orexin and binge-like consumption: sucrose, saccharin, ethanol andy deemer

Orexin and binge-like consumption:

Sucrose, Saccharin, Ethanol

ANDY DEEMER

Bingeing• Eating, Drinking, Drugs

• Orexin plays a role but…• Caloric Status? (Non-)Caloric reward?

• Conditioning? Cue-induced reward seeking

• ♂ ♀ differences?

• Inconsistencies in several studies

• Methodology related? Gender related?

• Gender Differences• Orexin system

• ♀ rat - higher Orexin A and OXR1 in HL than ♂• Responses to food restriction• More studies = more differences revealed.

Economic, Social and Therapeutic Potential of Orexin Research

• Overconsumption of ______________ is a significant public health/economic issue.

• Potential applications in obesity, diabetes, drug abuse

• Understanding factors at play = better therapy

• Caloric restriction important?

• Gender diffs?

• Bingeing substance (caloric/non, hedonic)

• Orexin system sexual dimorphism

• Eating disorders more common in women

• OX system gender differences may play a role

• Hedonic vs Homeostatic

• Saccharin vs sucrose

Cason & Aston-Jones 2014

Role of orexin/hypocretin in conditioned sucrose-seeking in female rats

Methods

• Female Sprague-Dawley rats

• Two Feeding Treatments

• Ad libitum (AL) = free access

• Food-restricted (FR) =

• 1 daily feeding - maintained at 85% of AL body mass)

• Drug = SB-334867 (OXR1 antagonist)• 3 doses used in this study 10, 20, and 30 mg/kg

• Intraperitoneal (4 mL/kg)"SpragueDawleyRat" by Jean-Etienne Minh-Duy Poirrier - http://www.flickr.com/photos/jepoirrier/422469518/in/set-72157594329856603/. Licensed under CC BY-SA 2.0 via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:SpragueDawleyRat.jpg#/media/File:SpragueDawleyRat.jpg


Methods• Training – self-administer sucrose pellets

• Press lever = get sucrose pellet

• Compound cue (light and sound)

• Fixed ratio (FR) 1 responding• Until 10 sessions earning > 9 sucrose pellets

• Progressive ratio (PR) responding• Using mice previously trained from FR experiment

• Find breakpoint for lever presses

Images adapted from: http://rnpsychology.org/demo/index.htm


Fixed vs Progressive Ratio Schedule

Progressive Ratio = 5ePelletNumber*0.2 – 5

Point at which no more rewards are earned over an hour = breakpoint.


Methods - Ratio Experiments

Fixed Ratio:

Train Vehicle/Drug injection Self-administration session

Progressive Ratio:

Use rats from fixed ratio experiment Train Injection

Self-administration session

Each rat was tested at multiple doses (2 doses)

Vehicle/Drug injected 30 minutes prior to

test sessions (all 3 of today’s papers)


Cue-induced reinstatement of sucrose-seeking

• Take mice used for FR1 (but not PR)

• Daily extinction sessions

• Lever presses = nothing happens• Untraining

• Until 2 consecutive sessions with < 25 active lever presses

• Bring cues back (but no sucrose)

• Measure SB effect on presses

• 2 late extinction and 2 reinstatement sessions


Self-Admin Training

• # days to train similar for FR and AL rats

• Food-restricted

• More active and inactive presses + pellets earned


Fixed Ratio Experiment

• FR more active presses + pellets earned

• SD sig. effect on active presses only at high dose

• No sig. effect of SD on pellets earned


Progressive Ratio Experiment

• No effect of group or SB dose on breakpoint


Cue-induced reinstatement of sucrose-seeking

• Food group effect• No sig. SB effect on

CIRSS• Contrary to their previous

findings in ♂ rats

• AL and FR rats met extinction criteria < 5 extinction sessions

• SB attenuation of active presses - late extinction


Cason & Aston-Jones Take Homes

• Cue-induced reinstatement and SB-334867

• Sex-dependent story

• ♀ - OXR1 unnecessary; important in ♂

• Increased extinction responding • Orexin role in learning/reward valuation in females?

• Future Research: • Systems at play in ♀ cue-induced seeking (e.g. leptin, insulin,

ghrelin, estrogen)

• Untangling ♂ ♀ circuitry differences

• SB-334867 effects on Fos expression in orexin targets


Cason & Aston-Jones Take Homes

• Agree with conclusion?

• “Our findings show that OxR1 regulates operant responding for sucrose reinforcement, but not motivation to work…”

• Fig 4, Panel 1:

With OXR1 unblocked, try less = regulates motivation to work?


• Objectives:

• SB-334867 effect on binge consumption of sucrose and saccharin in ad libitum-fed mice

• Effect of repetitive sucrose and saccharin bingeing on OX mRNA expr in LH• Mirror chronic morphine, cocaine, ethanol?

Binge-like consumption of caloric and non-caloric palatable substances in ad libitum-fed C57BL/6J mice: Pharmacological and molecular evidence of orexin involvement

Alcaraz-Iborra et al. 2014

Methods

• Male C57BL/6J (8 wks old @ start)

• Drug = SB-334867 (OXR1 antagonist)

• Intraperitoneal (10 mL/kg)

• Drinking-in-the-Dark (DID) procedure

• High voluntary bingeing on ethanol, sucrose, saccharin during early part of dark cycle

• Provide sucrose/saccharin ~ 3 hrs. into dark cycle

• Open-field activity monitoring

• qPCR


Experiment 1: Effect of SB on sucrose and saccharin binge

drinking• Binge-training / screening

• 3 days of DID (2 hrs bottle access)• ip injection w/ vehicle - habituation

• 4th day = test day (4 hrs bottle access)• Injection of SB (10, 20 or 30 mg/kg) or vehicle 30 min prior to test

• Measure:• Liquid imbibed

• Calories consumed (chow included)


Total calories consumed (kcal/g/4 h) on test day

Sucrose group

(kcal/g)Saccharin group

(kcal/g)VEH 3.47 ± 0.20 2.74 ± 0.42

SB (10 mg) 2.24 ± 0.14** 0.20 ± 0.09**SB (20 mg) 1.11 ± 0.28** 1.24 ± 0.49**SB (30 mg) 0.97 ± 0.19** 0.64 ± 0.39**

*

• ip SB-334867 ↓ sucrose and saccharin bingeing

• Higher doses ↓ sucrose bingeing more than lowest dose

• Strange calories consumed data in saccharin group


Experiment 2: Effect of SB on locomotor activity

• Open-field locomotor activity monitoring• Days 1-3: Habituate to injection (vehicle) and activity chamber & record behavior

• Day 4: 30 mg/kg SB → activity chamber

• Evaluate difference

• Purpose: SB-334867 impact distance traveled and movement time?• Explanation for reduced fluid/food intake?

• Results: No sig. diff.• The means they present seem fairly different, but no sig. diff


Experiment 3: Repeated sucrose/saccharin bingeing and mRNA expression

in the HL

• Repeated bingeing (DID – i.e. voluntary)• Four 2-hour daily binge sessions

• Sucrose, Saccharin, or Water group

• Brain dissection → LH removed → RNA extracted

• qPCR with GAPDH for comparison


Consumption data (ml/kg/2 h) associated with the mRNA study.

Water consumption (ml/kg/2 h)

Sucrose consumption (ml/kg/2 h)

Saccharin consumption (ml/kg/2 h)

Day 1 34.40 ± 0.64 72.42 ± 8.78 67.70 ± 6.86

Day 2 23.42 ± 3.50 117.72 ± 10.46 94.41 ± 15.24

Day 3 22.14 ± 0.87 125.80 ± 4.16 77.88 ± 6.87

Day 4 21.12 ± 2.29 103.74 ± 8.07 86.69 ± 3.64

• Repeated bingeing ↓ HL OX mRNA

• Sucrose group: 5x > water intake


Alcaraz-Iborra et al. 2014: Take-homes

• OXR1 role in caloric bingeing in AL-fed animals

• SB-334867 ↓ caloric & non-caloric bingeing in AL-fed ♂ mice

• Unclear why in AL-fed mice (ip injection)• Future Research: Site-directed SB studies

• 1st evidence of OXR1 role in non-caloric bingeing/hedonic overconsumption

• Repeated daily bingeing ↓ HL OX expr (qPCR)

Alcaraz-Iborra et al. 2014: Take-homes

• SB effect on bingeing not caused by SB-altered locomotion.

• Why not show more data?

• DID potential issue:

• Energy status at time of DID

• Future Research: Alter energy status during DID

Binge-like consumption of Ethanol and Other Salient Reinforcers is Blocked by

Orexin-1 Receptor Inhibition and Leads to a Reduction in Hypothalamic Orexin

Immunoreactivity

Olney et al. 2015

Illustration by Emily Coren.

Purpose

• Characterize OXR1 role in “binge” drinking

• Ethanol, sucrose, saccharin

• Binge-like EtOH and Sucrose drinking

• Effect on OX immunoreactivity in HL

• Effect of ip SB

• SB specificity for EtOH modulation

• Compare with saccharin bingeing

Olney et al. 2015

Methods

• C57BL/6J male mice (7-9 wks old)

• SB-334867 (0, 5, 10 mg/kg)

• Bingeing cycles:

• 1 or 3 cycles; EtOH or Sucrose

• DID (modified 2 hrs not 4 – short drug action)

• Except experiment 1 – used 4 hrs.

• Blood alcohol content

• Brain dissection

• Orexin A immunoreacitivy (LH and PFA)

Olney et al. 2015

Methods

• SB ip injection

• Reduced EtOH consumption? Saccharin?

• Each mouse, all doses• 4 day cycle with 3 days rest between doses

• Locomotion

• Open field test with Saccharin group mice

• 2 hours

• 0 or 10 mg/kg SB

Olney et al. 2015

Olney et al. 2015

• No cycle effect on:

• EtOH Consump.• Sucrose Consump• BEC

• EtOH bingeing ↓ LH OX levels

Olney et al. 2015

EtOH Bingeing reduced HL OX

Olney et al. 2015

• SB ↓ EtOH consumption• Short-lived (Hr 1 vs. Hr 2)• BEC levels parallel total consumption

• SB ↓ Saccharin consumption• Only signif. largest dose over 2 hrs.

• Take Home: SB effect on ↓ bingeing not specific to EtOH or caloric foods

Olney et al. 2015

Locomotion

• Like Alcaraz-Iborra: • SB-induced general lethary

cause of reduced bingeing?

• Open field test: • No impairment of

locomoter activity

Olney et al. 2015: Take-homes• OXR1 role in caloric and non-caloric bingeing

• Not EtOH specific

• Bingeing ↓ HL OXR1

• SB effects not due to altered locomotion

• DID 4hr vs 2hr

• Duration of drug effect may be less than 4 hrs

• Inconsistent dose effects between researchers• SB variability: Supplier effects, batch effects

• Future Research:

• Mechanisms responsible for post-binge OX and OXR1 levels

• Interplay of dynorphin and OX w/in VTA

Overall Take-homes

Site-specific studies necessary (not ip injection)

- ID OX circuits underlying phenomena

- VTA likely involved

Thank You!

orexin and binge-like consumption: sucrose, saccharin, ethanol andy deemer

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