Nicotine Induces Estrus in Adult Female Rats

Rebecca Philip

Nicotine

• Mimics Ach• Binds to

NAChR Increases levels of dopamine

Females are more likely to become addicted to nicotine.

Why?

Estrous Cycle

Leukocyte

Proestrus Estrus Metestrus Diestrus

Metestrus Diestrus Proestrus Estrus

Estrogen

Progesterone

LH

FSH

Hormone Levels

Methods

Nicotine

30 m 60 m

Vaginal Cytology Injection30 m Post

Injection Swab60 m Post

Injection Swab

0.6 0.8 1 1.20

0.2

0.4

0.6

0.8

1

1.2

proestrus

estrus

metestrus

diestrus

dose (mg/kg)

stag

e (%

rats

)

The majority of rats transitioned into estrus stage following nicotine administration.

Pre-Injection: Proestrus30 m Post-Injection:

Estrus60 m Post-Injection:

Estrus

Slide Analysis

At 0.6 mg/kg nicotine rats continued to transition into estrus 30m and 60m post

injection

proestrus estrus metestrus diestrus0

0.2

0.4

0.6

0.8

1

1.2

0 m

30 m

60 m

stage

% ra

ts

ConclusionsNicotine administration induced estrus in adult female rats.

A lack of ovarian hormones could be related to the sex difference related to nicotine addiction.

Estrogen

Progesterone

LH

FSH

Before administration: no significance in % rats in each stage.

Nicotine could have caused:

• A decrease in the levels of ovarian hormones

• Desensitization of hormone receptors which mimicked a decrease in hormone levels

Progesterone

Estrogen

LHFSH

Discussion• Ovarian hormones

could serve as protection against the effects of drug addiction.

• Nicotine causes a decrease in estrogen and progesterone

they are not present to protect against its effects females become more susceptible to its effects

Could testosterone be more effective protection against the effects of nicotine?

At 1.2 mg/kg nicotine, rats experienced no change in stage 30 m and 60 m post administration.

proestrus estrus metestrus diestrus0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0m30m60m

stage

% ra

ts

Future Research

• No increase or decrease at the high dose

• Possible explanation:Desensitization after 2 weeks of administration.

• Are females also more likely to become desensitized?

Peak transition into estrus occurred at 0.8 mg/kg nicotine.

0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.30.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

Dose (mg/kg)

% in

crea

se in

rats

Future Research

• Dose response curve for nicotine administration is incomplete.– More research is

necessary on the relationship between hormone action and dose.

• The exact mechanism for nicotine’s interaction with ovarian hormones is not clear.