Background: Sex differences in cocaine abuse are well established. Females have a higher sensitivity and thus higher vulnerability to cocaine abuse compared to males. There are many studies showing that sensitivity to cocaine reward varies during the estrus cycle.
Methods: Vaginal smears were examined through a DIFF staining kit and viewed through a microscope to determine the estrus cycle stage. Smears were taken immediately before and after cocaine and/or caffeine injections. Furthermore, we suggest a new tool to analyze the estrus cycle by using electrical resistance of the vaginal mucosa.
Results: In the present study, we discovered that cocaine directly induced changes in the estrus cycle. Interestingly, caffeine did not affect the estrus cycle and nor did the combination of cocaine and caffeine. We observed that caffeine blocked the cocaine-induced estrus cycle changes using conventional exfoliate cytology. Therefore, caffeine may have neuroprotective properties on the changes induced by cocaine.
Conclusion: These phase changes in the estrus cycle may be the underlying cause of sex differences in cocaine addiction that can be blocked by caffeine. Thus, we propose a valuable insight into sex differences in cocaine abuse and reveal a possible treatment with antagonizing the adenosine system.
Introduction
Cocaine abuse is seen in more than 1.8 million Americans, and the number of women users is increasing at an alarming rate.1 Given the highly addictive properties of cocaine, this phenomenon has become a public health concern. Cocaine significantly increases neurotransmitters, such as dopamine (DA) and serotonin, in the reward areas of the brain.2 More and more evidence is pointing to the increased vulnerability of cocaine abuse in women compared to men.3 In laboratory animals, females self-administer cocaine more rapidly, become dependent earlier, and relapse faster compared to males. However, the reason for these sex differences remains uncertain.
Sex hormones, such as estrogen, are regarded as the underlying cause. Estrogen levels fluctuate throughout the four stages of the estrus cycle.4 Laboratory animals with higher estrogen levels also have higher sensitivity to cocaine.
If you are interested in learning more about this. Then click here.