Neurochemistry International, Vol. 5, No. 2, pp. 185 to 192, 1983 0197-0186/83/020185-08503.00/0 Printed in Great Britain © 1983 Pergamon Press Ltd.

COMMENTARY

NEUROTRANSMITTER-CONTROLLED STEROID HORMONE RECEPTORS IN THE CENTRAL NERVOUS

SYSTEM*

DANIEL P. CARDINALIt, MARIA I. VACASt, MONICA N. RITTA~ and PABLO V. GEJMAN~

Centro de Estudios Farmacol6gicos y de Principios Naturales, (CEFAPRIN), Serrano 665, 1414 Buenos Aires, Argentina

(Received 3 Auoust 1982; accepted 24 September 1982)

Al~traet--Results are discussed indicating that neurotransmitters affect steroid hormone activity not only by controlling via neuroendocrine events the hypophysial-gonadal and hypophysial-adrenal axes, but also by modulating cell responsiveness to steroids in target cells. Hyper- or hypoactivity of pineal nerves result in enhancement or impairment of estradiol and testosterone effects on pineal metabolism in vivo and in vitro. Pineal cytoplasmic and nuclear estrogen and androgen receptors are modulated by norepinephrine released from nerve endings at the pinealocyte level. Neural activity affects the cycle of depletion-replenishment of pineal estrogen receptors following estradiol administration. Another site of modulation of steroid effects on the pinealocytes is the intracellular metabolism of testosterone and progesterone; nerve activity has a positive effect on testosterone aromatization and a negative effect on testosterone and progesterone 5ct-reduction. NE activity on the pineal cells is mediated via fl-adrenoceptors and cAMP. In the central nervous system information on the neurotransmitter modulation of steroid hormone action includes the following observations: (a) hypothala- mic deafferentation depresses estrogen receptor levels in rat medial basal hypothalamus; (b)changes in norad- renergic transmission affect, via ~-adrenoceptors, the estradiol-induced increase of cytosol progestin receptor concentration in guinea pig hypothalamus; (c) cAMP increases testosterone aromatization in cultured neurons from turtle brain; (d) electrical stimulation of dorsal hippocampus augments, and reserpine or 6-hydroxy- dopamine treatment decrease, corticoid binding in cat hypothalamus. In the adenohypophysis changes in dopaminergic input after median eminence lesions or bromocriptine treatment of rats result in opposite modifi- cations of pituitary estrogen receptor levels. Therefore all these observations support the view that neurotrans- mitters can modulate the attachment of steroid hormones to their receptors in target cells.

During the 20 years elapsed since the initial obser- vations by Jensen and his co-workers on the binding of radiolabeled estradiol of high specific activity to uterine target cells, emphasis on steroid hormone research has been on the sequential metabolic changes initiated by the interaction of the hormone with its receptors, paying relatively less attention to the possible occurrence of modulatory influences on the major primary event (Jensen and Jacobson, 1960; Baulieu et al., 1975; Gorski and Gannon, 1976; Grody et al., 1982). However, in the last few years it has increasingly been recognized that besides the main dynamic relationship described above, an array of en-

* Studies from authors' Laboratory were supported by grant No. 6638 from Consejo Nacional de Investigaciones Cientificas y T6cnicas (CONICET), Argentina.

t Established Investigator, CONICET. :~ Research Fellow, CONICET.

dogenous and exogenous factors modulate the final response of the target cells to the steroid hormone (Muldoon, 1980). This article deals with the results obtained when one of those factors, i.e. the functional state of the afferent neuronal pathways, is assessed. Such relationship between nerve activity and cell re- sponse to the steroid hormone can be of importance in the modulation of steroid hormone effects on the CNS.

CONTROL BY SYMPATHETIC NERVES OF RECEPTORS, METABOLISM AND

BIOLOGICAL ACTIVITY OF STEROIDS IN THE PINEAL GLAND

Modulation of steroid hormone receptor activity by neurotransmitter is a phenomenon that was first de- scribed, and is most thoroughly known in the pineal

185

186 DANIEl_ P. ('ARDINAI I t ' l ~ll.

gland. This is partly due to the particular neuroendo- crine properties of the gland as well as to its easily accessible and manipulable innervation and homo- geneous cell structure (Cardinali, 1979, 1982). In mammals the pineal gland is an endocrine organ with some of the properties of a neuroendocrine transducer (Wurtman and Axelrod, 1965; Reiter, 1980). One of its major functions is to convert an input of neural sig- nals, namely norepinephrine (NE) released from the pineal sympathetic nerve endings to a hormonal out- put. i.e. methoxyindoles and polypeptides. In ad- dition, an increasing amount of evidence indicates that the pineal gland and its innervating sympathetic neurons located in the superior cervical ganglia (SCG) are active points of concurrency for hormonal signals carrying information from the internal milieu (Cardinali, 1981).

Steroids affect pineal structure and metabolism (for references see Cardinali, 1981). Estradiol treatment has been reported to influence a number of pineal constituents including size and matrix of pinealocyte mitochondria, lipid, nucleic acid and protein content, protein and RNA synthesis, progesterone metabolism, serotonin and NE turnover rates, NE-induced in- crease of adenyl cyclase activity and of cAMP con- tent, NE-induced changes of pineal electrical activity, hydroxyindole-O-methyl transferase (HIOMT) levels and melatonin release. Pineal metabolic activities and constituents that have been reported as affected by testosterone administration include protein synthesis, serotonin and NE turnover rates, HIOMT and mono- amine oxidase activities and pineal electrical activity. Progesterone treatment depressed rat pineal HIOMT, protein synthesis and melatonin release i~ vivo and in vitro, while corticoid removal modified the pineal perivascular contact area and HIOMT activity.

The pre-requisite for the existence of direct effects of hormones on pineal cells, i.e. the existence of hor- mone binding to pineal tissue, has been investigated both in vivo and in vitro. Experiments carried out in animals injected with labeled steroids, or on subcellu- lar fractions incubated with different radioactive hor- mones indicate that the pineal gland of various spe- cies (rat, sheep, cow, rhesus monkey) contains protein components which bind the hormone with high affin- ity and specificity. To date, putative receptors for estradiol (Cardinali et al., 1975; Cardinali, t977), testosterone [Cardinali et al., 1974), 5~-dihydrotestos- terone (5-DHT) (Cardinali et al., 1974}, progesterone (Vacas et al., 1979), prolactin (Cardinali, 1982) and melatonin (Vacas and Cardinali, 1980) have been detected in pineal subcellutar fractions (Fig. 1). Bio- chemical data about pineal steroid receptors have

received confirmation from autoradiographic studies: rats injected with tritiated estradiol, testosterone or 5-DHT exhibited nuclear incorporation of radioac- tivity in pineal cells (Stumpf and Sar, 1977). Enzyma- tic activities that reduce testosterone and progester- one in C3 and C5 positions are also present in the pinealocytes; additionally testosterone is aromatized to estradiol by the rat pineal gland (Cardinali et al.. 1974: Hanukoglu et al., 1977). Recently we observed that NE added to incubated rat pineal glands enhanced via fl-adrenoceptors and cAMP the aroma- tization of testosterone, while inhibited testosterone reduction to 5-DHT and 5~-androstanediol (5~-diol); likewise NE inhibited the 5a-reductive pathway of progesterone in pineal explants (Cardinali et al..

1982al. The first indication that the activity of the sympath-

etic nerves innervating the pineal gland may control the sensitivity of the gland to circulating estrogen or androgen was provided by the observation that superior cervical ganglionectomy (SCGx) depressed both cytoplasmic and nuclear hormone binding sites and inhibited hormone-induced increase of pineal tein synthesis (Cardinali et al., 1975, 1976). The ad- ministration of NE restored the depressed cytoplas- mic estrogen and androgen binding sites in SCGx rats; these effects were mediated by a /3-adrenoceptor and through changes in RNA synthesis. Further sup- porting this conclusion, sucrose gradient analysis revealed that isoproterenol treatment of SCGx rats increased significantly pineal cytosol estrogen and androgen receptor levels (unpublished results); such an effect on the estrogen receptor is shown in Fig. 2.

In the pineal gland of the adult spayed rat, cytosol estrogen receptors undergo a cycle of depletion and replenishment during the 18 h that follow a single injection of 2 #g of estradiol (a dose which achieved pineal estrogen receptor changes resembling those of the morning of proestrus in intact rats), (Cardinali, 1977). This observation is in general agreement with the results obtained when the depletion-replenish- ment pattern of hypothalamic and adenohypophysial estrogen receptor was examined in castrated rats (Muldoon, 1980; Lieberburg et al., t980; Leibl and Spona, t982; Cardinali et al., 1983).

After 1 week SCGx caused a significant impairment of the estradiol-induced translocation of estrogen- receptor complexes from pineal cytosol to nuclei (Cardinali, 1977). The effect of SCGx was only par- tially reversed by isoproterenol treatment, the/3-adre- noceptor agonist restoring cytoplasmic estrogen receptor levels but failing to affect the translocation to the nuclei. Blockage of/~-adrenoceptors by proprano-

Neurotransmitters and steroid receptors in CNS 187

PINEALOCYTE

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T r~ P Fig. 1. A hypothetical scheme of neurotransmitter-controlled steroid hormone receptor activity in rat pineal gland. NE released by the nerve ending acts on fl-adrenoceptors of the pineal cells to stimulate the activity of adenyl cyclase (Weiss and Costa, 1968). NE also acts on pineal ct-adrenoceptors (Vacas et al., 1980) with a concomitant increase in phosphatidylinositol turnover (Smith et al., 1979) and PGE2 synthesis (Ritta and Cardinali, 1982). Two apparently opposite effects on adenyl cyclase may result from the ct-adrenoceptor-mediated mechanism, since PGE2 stimulates via postsynaptic receptors pineal cAMP synthesis (Ritta and Cardinali, 1981) while an ct-adrenoceptor-mediated inhibition of adenyl cyclase has been reported in various tissues (Exton, 1981). The net increase in intracellular cAMP levels elicited by NE interaction with its receptors stimulates pineal RNA and protein synthesis (Morrisey and Lovenberg, 1978a,b) and melatonin synthesis and release (Wurtman et al., 1971). Additionally NE per se, via presynaptic adrenoceptors (Pelayo et al., 1977) or through increased PGE2 concentration in the synaptic cleft (Cardinali et al., 1982b), modulates its own release from pineal sympathetic nerve endings. NE via fl-adrenoceptors and cAMP stimulates testosterone (T) aromatization and inhibits T and pro- gesterone (P) 5or-reduction (Cardinali et al., 1982a). NE also controls the levels of cytoplasmic T, 5~-dihydrotestosterone (DHT) and estradiol (E2) receptors (R) (Cardinali et al., 1975), as well as the translocation of E2R to nuclei (Cardinali, 1977). PR (Vacas et al., 1979), melatonin R (Vacas and Cardinali, 1980) and prolactin (PRL) R (Cardinali, 1982) are present in pineal subcellular fractions.

Several other hormones affect also pineal function partly through changes in afferent neural input.

1ol inhibited partially estradiol-induced translocation of hormone-receptor complexes to the nuclei. Collec- tively these results led to the conclusion that although the sympathetic input was needed to keep the cycle of deplenishment-replenishment of cytosol estrogen receptor intact, repetitive injection of the fl-agonist isoproterenol failed to restore this parameter in SCGx rats. Perhaps the schedule of isoproterenol treatment (due to sequential changes in super and subsensitivity after pulse isoproterenol injection) failed to reproduce the normal interaction of NE with its pineal fl-adre- noceptors; alternatively another nerve-originated input besides NE might keep pineal estrogen receptor kinetics normal (Cardinali e t al., 1983).

In order to analyze some of these possibilities we took advantage of the so-called 'degeneration activity' of a sympathetically-innervated organ that follows the interruption of the neural input to the organ (Emme- lin and Trendelenburg, 1972; Stefano e t al., 1974; H~iggendal, 1980). In the salivary glands and the nicti- tating membrane SCGx is followed by a release of NE from the varicosities that begins at the 8-10th h and elapses for about 10-12h until the degeneration of terminals is completed. The transient adrenergic hyperactivity observed in the organ can be a useful tool to study the physiological meaning of the organ's sympathetic innervation. In the rat pineal gland the degeneration of sympathetic nerves, as measured by

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Fig. 2. Sedimentation pattern of the binding of aH-estradiol (E2) to rat pineal cytosol of spayed rats subjected to SCGx 7 days earlier (left panel) (Cardinali et al., 1975) or to SCGx 7 days earlier plus the s.c. injection of 1-isoproterenol (5 mg/kg) 19 and 3 h earlier (right panel) (unpublished results). Cytosols were incubated for 5 h at 0°C with 14 nM all-E2 in the presence or absence of 1 #M unlabeled E2. Incubated cytosols were layered on linear gradients of 5-20% sucrose in Tris-EDTA-mercaptoethanol buffer and was centrifuged for 18 h at 37,000rev/min in a Spinco SW 39 rotor. BSA: bovine serum

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the decay in pineal NE content, is observed as early as 8-10 h after SCGx, and ends about 10 h later (Mor- gan and Hansen, 1978). Interestingly enough, translo- cation of cytoplasmic estrogen receptor complexes to

the nuclei was maximal in the pineal gland of estra- diol-treated rats during the post-SCGx degeneration of nerves, and was impaired either prior or after this time (Cardinali e t al., 1983). Propranolol but not

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Fig. 3. Nuclear estradiol (E2) receptor complex concentration and conversion of ~4C-serotonin to 14C-5- methoxyindoles in rat pineal glands incubated in vitro for 10 h with estradiol, propranolol or phentol- amine. 14C-serotonin metabolites and 3H-E2 nuclear exchange were determined as described elsewhere (Cardinali, 1977). Methoxyindole synthesis was estimated as the sum of melatonin, 5-methoxytryptophol and 5-methoxy-indole-acetic acid fractions. Shown are the means _+ S.E.M. (N = 4 in each group)

(*)P < 0.05.

Neurotransmitters and steroid receptors in CNS 189

PINEAL " C - ~ F t O N E METABOLISM

RNEAL PROTEIN

SYNTHESIS PINEJ~ TESTOSTERONE RECEPTORS

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Fig. 4. Pineal ]4C-testosterone metabolism, protein synthesis and testosterone receptors in castrated male rats killed at the end of the dark (D) phase (0600 h) or in the middle of the light (L) phase (1400 h) of daily photoperiod. To study 14C-testosterone metabolism 8 pineal glands were incubated for 24 h in TC 199 medium and 14C-estradiol (E2), 5ct-dihydrotestosterone (5-DHT) and 5~t-androstanediol (5ct-diol) were measured after ether extraction, phenolic partition and thin layer chromatography (Cardinali et al., 1982). Shown are dpm/8 pineals (E2) or dpm/pineal (5~t-reduced metabolites) means + S.E.M. (N). Results on the effect of testosterone proprionate (TP) on pineal protein synthesis are reproduced from Nagle et al. (1975). Testosterone binding sites were examined as described elsewhere (Cardinali et al.,

1976); results are presented as Scatchard plots. (*) P < 0.05; (**)P < 0.01.

phentolamine impaired the 'degeneration' hypersti- mulation of estrogen receptor accumulation in pineal nuclei supporting the conclusion that both the levels of cytoplasmic estrogen binding sites and their translocation to the nuclei are under the control of sympathetic nerves via a fl-adrenoceptor (Fig. 1).

In v i tro the degeneration of pineal sympathetic nerves endings is expected to occur shortly after the initiation of cultures due to the lack of a 'protective' effect of a long axonal stump (which accounts for the latency observed after SCGx) (Emmdin and Trende- lenburg, 1972; H~iggendal, 1980). Addition of estradiol to the culture medium of flesh pineal explants brought about a significant increase of both nuclear estradiol-receptor complex levels and serotonin con- version to methoxy-indoles (Cardinali, 1977). Either a 10h-preincubation period (to allow complete de- generation of nerve endings) or the addition of pro- pranolol (Fig. 3) blocked estradiol effects. Thus, as in vivo, the continuous interaction of NE with poadreno- ceptors appears to be an absolute requirement for controlling both translocation and physiologic effects of estradiol in the pineal gland.

Another physiological example of neuronal modu- lation of pineal responsiveness to circulating hormone signals was given by studies at different times of the day in rats. In male rats pineal response to androgens as well as to other hormones, e.g. ACTH (Schotman et al., 1981) depends largely on the time of day when the hormone is injected (Fig. 4). The extent of stimu- lation of pineal protein synthesis brought about by testosterone parallels the daily rhythm in pineal NE content and turnover (Brownstein and Axelrod, 1974), pineal testosterone uptake in vivo (Nagle et al., 1974) and pineal testosterone receptor levels (Fig. 4) in that all these reach maximal values during the night. At this time testosterone aromatization was high whereas testosterone 5~-reduction was low (Fig. 4). Recently time-dependent effects of testosterone on pineal elec- trical activity (Semm et al., 1981) and cAMP-phos- phodiesterases (Epplen et al., 1982) have been reported. Collectively these results indicate that the overall effect of testosterone on the pinealocytes depends on the level of activity of the innervating sympathetic neurons through regulation of hormone binding sites and metabolism in target pineal cells (Fig. 1).

191) D A N I I I P. ( ' A R D I N A l l tq ~ll.

N EU ROTRANSMITTER-MEDIATED CONTROl. OF STEROID RECEPTORS AND ACTION IN THE CNS AND THE

ADENOHYPOPHYSIS

In order to test the proposition that steroid action within brain target cells is modulated by neurotrans- mitters, Nock et al. (1981) carried out a detailed study in female guinea pigs in which lordosis (a steroid- dependent behavior) is influenced by NE trans- mission. In a first experiment they examined the effect of the dopamine-/3-hydroxylase inhibitor U-14,624 on cytoplasmic progestin receptor in estrogen-primed female guinea pigs. Twelve hours after drug adminis- tration a 36°; less progestin receptor was detectable. Activation of :~-adrenoceptors with clonidine com- pletely reversed the effect of U-14,624, which was not attributable to competition of the drug with the radioligand used for receptor binding studies, nor to a decreased affinity of the receptor.

Blockade of :~-adrenoceptors by phenoxybenzamine resulted in a relative reduction of hypothalamic bind- ing sites for progestins (Nock et al., 198t). There was a 3-4 h delay between ~-adrenoceptor blockage and progestin receptor decline, a finding which supports the concept that as in the pineal gland and the adeno- hypophysis (see below) a continuous intereaction of neurotransmitter with its receptors was needed to keep steroid responsiveness of target cells normal. The changes in hypothalamic progestin concentration following adrenergic drugs could not be explained by modifications of circulating progesterone levels. Since phenoxybenzamine was unable to alter hypothalamic progestin receptors in the absence of estrogen priming Nock et al. (1981) concluded that changes in NE transmission were due to interference by the drug with the estrogen-induced increase of those receptors.

Carrillo and Sheridan (19801 provided also evidence that estrogen activity in rat hypothalamus is modu- lated by the neural input via modification of receptor levels. Complete deafferentation of the hypothalamus caused a 50}o-reduction in cytosol estrogen receptors without changing receptor levels in the preoptic area. These data are compatible with the phenotiazine- induced decrease of 3H-estradiol uptake in rat median eminence reported by Shani et al., (1976), as well as with the observation on a diurnal rhythm of hypo- thalamic cytoplasmic estrogen receptors in the absence of circulating estrogens described by Roy and Wilson (1981).

There is evidence that aromatization is a key meta- bolic pathway to mediate certain neuroendocrine and behavioral responses to testosterone in the CNS

(McEwen, 1980). By regulating the amounts of estro- gen available for binding with receptors in target neurons, changes in aromatase activity can be one of the ways of modulating target organ response. Recently Callard (1981! reported that dibutyryl cAMP added to primary neuronal cultures from aduh turtle brain increased estrogen synthesis from testos- terone. Hence, as shown for the mechanisms by which NE controls estrogen receptor levels and effects in the pineal gland and hypothalamus, the basic processes underlying neurotransmitter modulation of intracellu- lar testosterone metabolism may be the same regard- less of the neuroendocrine region examined.

The sensitivity of hypothalamic cells to adrenal steroids appears also to be influenced by the activity of neurons innervating the hypothalamus. Stith et al.

(1976) demonstrated that the electrical stimulation of the dorsal hippocampus, but not of the amygdala, caused an increase in the uptake and nuclear binding of -~H-cortisol by cat hypothalamic cells. Reserpine or 6-hydroxydopamine treatment depressed 3H- dexamethasone binding in hypothalamus and hippocampus, suggesting again a neurotransmitter modulation at the steroid receptor level (Stith and Weingarten, 1979; Stith and Person, t982).

To study the possible influence of the CNS on pituitary steroid receptors Weinsenberg et al. (1979) examined the binding and uptake of estradiol in the adenohypophysis and hypothalamus of rats bearing median eminence lesions. A time-course study indi- cated that the binding of 3H-estradiol in the adeno- hypophysis was lower than normal as early as 1 h after lesion placement, and remained depressed for at least 21 days. Of the two possible signals involved in the changes observed, namely increased plasma prolactin levels or suppressed dopamine input to the adeno- hypophysis, the former could be ruled out since in rats rendered hyperprolactinemic by anterior pituitary transplants under the kidney capsule, estrogen receptor levels of the in situ pituitaries were similar to those of the nongrafted controls (De Nicola et al.,

1981). Moreover administration of the dopamine agonist bromocriptine restored adenohypophysial estrogen receptor levels in animals bearing median eminence lesions. Therefore De Nicola et al. (1981) postulated that when dopamine is prevented from reaching the pituitary via the portal vessels, there is a reduction in estradiol binding in parallel to the incre- ment in serum prolactin levels. These observations largely extend the concept that as in the pineal gland and the brain neurotransmitters modulate the attach- ment of a steroid hormone to its receptors in the adenohypophysis.

Neurotransmitters and steroid receptors in CNS 191

CONCLUDING REMARKS

The major idea underlying the foregoing discussion is that the basic processes of neuroendocrine integra- tion occur at all neuroendocrine structures regarde- less of their cellular or biochemical complexity. Deriv- ing from experiments first carried out in the pineal gland and later extrapolated to the brain and pitui- tary the general hypothesis can be put forth that in addition to the two major relationships between steroids and brain neurotransmitters described inso- far, namely steroid-modulated changes in neuro- transmission and neurotransmitter-regulated modifi- cations in steroid hormone secretion (via neuroendo- crine events in the hypothalamic-hypophysial axis), a third type of interaction arises. Modulation of cell responsiveness to steroids can be an important mech- anism by which neuronal activity affect hormone- dependent processes in neuroendocrine structures. Further experiments will test the general heuristic val- idity of this neuroendocrine concept.

REFERENCES

Baulieu, E.-E., Atger, M., Best-Belpomme, M., Corvol, P., Courvalin, J.-C., Mester, J., Milgrom, E., Robel, P., Rochefort, H. and De Catalogne, D. (1975). Steroid hor- mone receptors. Vitams Horm. 33, 649-736.

Brownstein, M. and Axelrod, J. (1974). Pineal gland: 24-hour rhythm in norepinephrine turnover. Science, N.Y. 14B, 163-165.

Callard, G. V. (1981). Aromatization is cyclic AMP-depen- dent in cultured brain cells. Brain Res. 204, 461464.

Cardinali, D. P. (1977). Nuclear receptor estrogen in the pineal gland. Modulation by sympathetic nerves. Neuro- endocrinology 24, 333-346.

Cardinali, D. P. (1979). Models in neuroendocrinology. Neurohumoral pathways to the pineal gland. Trends Neurosci. 21, 250-253.

Cardinali, D. P. (1981). Hormone effects on the pineal gland. In: The Pineal Gland. Vol. I. Anatomy and Bio- chemistry (Reiter, R. J., ed.), pp. 243-272. CRC Press, Boca Raton, FA.

Cardinali, D. P. (1982). Molecular mechanisms of neuro- endocrine integration in the central nervous system. An approach through the study of the pineal gland and its innervating sympathetic pathway. Psychoneuroendocrin- ology 7.

Cardinali, D. P., Gejman P. V. and Ritta, M. N. (1983) Further evidence on adrenergic control of intracellular levels and translocation of estrogen receptors in rat pineal gland. Endocrinology, in press.

Cardinali, D. P., Gomez, E. and Rosner, J. M. (1976). Changes in 3H-leucine incorporation into pineal pro- teins following estradiol or testosterone administration: Involvement of the sympathetic superior cervical gang- lion. Endocrinology 94, 849-858.

Cardinali, D. P., Nagle, C. A. and Rosner, J. M. (1974). Metabolic fate of androgens in the pineal organ: Uptake, binding to cytoplasmic proteins and conversion of

testosterone into 5~-reduced metabolites. Endocrinology 95, 179-187.

Cardinali, D. P., Nagle, C. A. and Rosner, J. M. (1975). Control of estrogen and androgen receptors in the rat pineal gland by catecholamine transmitter. Life Sci. 16, 93-106.

Cardinali, D. P., Ritta, M. N. and Gejman, P. V. (1982a). Norepinephrine stimulates testosterone aromatization and inhibits 5~-reduction via fl-adrenoceptors in rat pineal. Mol. Cell. Endocr. 28, 199-209.

Cardinali, D. P., Ritta, M. N., Pereyra, E. and Gonzalez Solveyra, C. (1982b). Role of prostaglandins in rat pineal neuroeffector junction. Prostaglandin E2 increases mela- tonin secretion and impairs norepinephrine release in vitro. Endocrinology, l l l , 53(~534.

Carrillo, A. J. and Sheridan, P. J. (1980). Estrogen receptors in the medial basal hypothalamus of the rat following complete deafferentation. Brain Res. 186, 157-164.

De Nicola, A. F., Weisenberg, L., Arakelian, M. C. and Libertun, C. (1981). Effects of bromocriptine on [aH]es- tradiol binding in cytosol of anterior pituitary. Endocrin- ology 109, 83 86.

Emmelin, N. and Trendelenburg, U. (1972). Degeneration activity after parasympathetic or sympathetic denerva- tion. Rev. Physiol. biochem, exp. Pharmacol. 66, 148-204.

Epplen, J. T., Kaltenhauser, H., Engel, W. and Schmidtke, J. (1982). Pattern of cyclic AMP phosphodiesterases in the rat pineal gland: Sex differences in diurnal rythmi- city. Neuroendocrinoloyy 34, 4654.

Exton, J. H. 0981). Molecular mechanisms involved in ~t-adrenergic responses. Mol. Cell. Endocr. 23, 233 264.

Gorski, J. and Gannon, F. (1976). Current models of steroid hormone action: A critique. A. Rev. Physiol. 38, 425450.

Grody, W. W., Schrader, W. T. and O'Malley, B. W. (1982). Activation, transformation and subunit structure of steroid hormone receptors. Endocrine Rev. 3, 141-163.

Hiiggendal, J. (1980). The disappearance of dopamine-fl- hydroxylase from the rat salivary glands after extirpation of the superior cervical ganglion. J. Neural. Trans. 48, 249-260.

Hanukoglu, I., Karavolas, H. J. and Goy, R. W. (1977). Progesterone metabolism in the pineal gland, brain stem, thalamus and corpus callosum of the female rat. Brain Res. 125, 313-324.

Jensen, E. V. and Jacobson, H. I. (1960). Fate of steroid estrogens in target tissues. In Biological Activity of Steroids in Relation to Cancer. (Pincus, G. and Vollmer, E. P., eds), pp. 161-178. Academic Press, New York.

Leibl, H. and Spona, J. (1982). Differential stimulation by 17fl-estradiol and synthetic estrogens of progesterone- receptor and of translocation of estrogen-receptor in rat pituitary and uterus. Endocrinology 110, 265-271.

Lieberburg, I., MacLusky, N. and McEwen, B. S. (1980). Cytoplasmic and nuclear estradiol-17fl binding in male and female rat brain: Regional distribution, temporal aspects and metabolism. Brain Res. 193, 487-503.

McEwen, B. S. (1980). Binding and metabolism of sex steroids by the hypothalamic-pituitary unit: Physiologi- cal implications. Ann. Rev. Physiol. 42, 97-110.

Morgan, W. W. and Hansen, J. T. (1978). Time course of the disappearance of pineal noradrenaline following superior cervical ganglionectomy. Exp. Brain Res. 32, 429434.

N.C.L 5/2 c

192 I ) A N I I [ P. ( 'ARI ) INAI 1 et Ill.

Morrisey, J. J. and Lovenberg, W. 11978a). Synthesis of RNA in pineal gland during serotonin-N-acetyltransfer- ase induction. Biochem. Pharmae. 27, 551 555.

Morrisey, J. J. and Lovenberg, W. (1978b). Protein syn- thesis in pineal gland during serotonin. N-acetyltransfer- ase induction. Arch. biochem. Biophys. 191, 1 7.

Muldoon, T. G. (1980). Regulation of steroid hormone ac- tivity. Endocrine Rev. I, 339 364.

Nagle, C. A., Cardinali, D. P. and Rosner, J. M. (1974). Diurnal rhythms in tissue radioactivity uptake after 3H-estradiol and 3H-testosterone administration to cas- trated rats. Steroids Lip. Res. 5, 107 112.

Nagle, C. A., Cardinali, D. P. and Rosner, J. M. (1975), Testosterone effects on protein synthesis in the rat pineal gland. Modulation by the sympathetic nervous system. L{tb Sei. 16, 81 92.

Nock, B., Blaustein, J. D. and Feder, H. H. (1981). Changes in noradrenergic transmission alter the concentration of cytoplasmic progestin receptors in hypothalamus. Brain Res. 207, 371 396.

Pelayo, F., Dubocovich, M. L. and Langer, S. Z. (1977) Regulation of noradrenaline release in the rat pineal through a negative feedback mechanism mediated by presynaptic :~-adrenoceptors. Eur. J. Pharmae. 69. 421 426.

Reiter, R. J. (1980). The pineal and its hormones in the control of reproduction in mammals. Endocrine Rev. 1, 109 131.

Ritta, M. N. and Cardinali, D. P. (1981). Prostaglandin E2 increases adenosine Y,5'-monophosphate concentration and binding site occupancy and stimulates serotonin-N- acetyltransferase activity in rat pineal glands in vitro. Molee. Cell. Endoer. 23, 151 159.

Ritta, M. N. and Cardinali, D. P. (1982). Involvement of :~-adrenoceptors in norepinephrine-stimulated prosta- glandin E2 release by rat pineal gland ill vitro. Neurosci. Lett. 31. 307 311,

Roy, E. J. and Wilson, M. A. {1981). Diurnal rhythm in cytoplasmic estrogen receptors in the rat brain in the absence of circulating estrogen. Science, N.Y. 213, 1525 t 526.

Schotman, P., Allart, J. and Gispen, W. H. (1981). Pineal protein synthesis highly sensitive to ACTH-like peptides. Brain Res. 219, 12t 136.

Serum, P., Demaine, C. and Vollrath, L. (1981). The effects of sex hormones, prolactin and chorionic gonadotrophin on pineal electrical activity in guinea pigs. Cell. molee. Neurobiol. 1,259 269.

Shani, J., Roth, Z.. Givant, Y., Goldhaber, G. and Sulman,

1-. G. 11976). Competition between [-~H]estradioJ and prolactin releasing phenotiazines for cstradiol receptors ill ritro. Israel J. reed. Sci. 12, 1338 1339.

Smith. T. L., Eichberg, J. and Heuser, G. (1979/. Postsyn- aptic localization of the alpha receptor-mediated stimu- lation of phosphatidylinositol turnover in pineal gland. L!I~' Sei. 24, 2179 2184,

Stefimo, F. J., Perec, C. J. and Tumilasci, O. R. 11974). Changes in neuronal uptake and metabolism of, and sen- sitivity to norepinephrine during the degeneration se- cretion in the rat submaxillary ghmd. J. Pharmae. exp. Ther. 191,403 417.

Stith, R. D. and Person, R. J. (1982). Effect of cenlral cate- cholamine depletion on 3H-dexamethasone binding in the dog. Neuroendocrinology 34, 410 414.

Stith, R. D., Person, R. J. and Dana, R. C. (1976}. Effects of hippocampal and amygdalar stimulation on uptake and binding of 3H-hydrocortisone in the hypothalamus of the cat. J. neurosci. Res. 2, 31% 322.

Stith, R. D. and Weingarten, D. P. (1979) Effect of a single injection of reserpine on kinetics of -~H-dexamethasone binding to receptors of the cat hypothalamus and hippo- campus. Neuroendocrinolo,qy 29, 363- 373.

Stumpf, W. E. and Sar, M. (1977). Steroid hormone target cells in the periventricular brain: Relationship to peptide hormone producing cells. Fed. Proc. 36, 1973-- 1983.

Vacas, M. I. and Cardinali, D. P. {1980) Binding sites for melatonin in bovine pineal gland. Hormone Res. 13, 121 131.

Vacas, M. 1., Lowenstein, P, R. and Cardinali, D. P. i1979}. Characterization of a cytosol progesterone receptor in bovine pineal gland. Neuroendocrinology 24, 84--89.

Vacas, M. I., Lowenstein, P. R and Cardinali, D. P. {1980). Dihydroergocryptine binding sites in bovine and rat pineal glands. J. Aut. Nerv. System. 2, 305 313.

Weisenberg, L., De Nicola, A. F., Arakelian, M. (7. and Libertun, C. (1979). Effect of median eminence lesions on E3H]estradiol binding in the anterior pituitary and hypothalamus. Endocrinology 10fi, 1152 -l 157.

Weiss, B. and Costa, E. 11968). Selective stimulation of ade- nyl cyclase of rat pineal gland by pharmacologically active catecholamines. J. Pharmac. exp. Ther. 101, 310~319.

Wurtman, R. J. and Axelrod, J. 11965). The pineal gland, Sci. Amer. 213, 50-60.

Wurtman, R. J., Sheim H. M. and Larin, F. (1971). Media- tion by beta-adrenergic receptors of effect of norepine- phrine on pineal synthesis of ~'*C serotonin and 14C melatonin. J. Neuroehem. 18, 1683- 1687.