Acute Cocaine Differentially Induces PKA Phosphorylation Substrates in Male and Female Rats

Background: Sex differences in intracellular dopamine pathways may contribute to the known sex differences in psychomotor responses to cocaine and differential development of dependence. This study aimed to determine whether there are sex differences in the activation of the extracellular signal-regulated kinases (ERK1/2, or p44/p42 MAPK) and PKA phosphorylation-dependent substrates in the nucleus accumbens (NAcc) of male and female rats at baseline or after acute cocaine administration. Methods: 60-day-old male and female Fischer rats were injected with saline or cocaine (30 mg/kg) and sacrificed 5, 15, 30, 45 or 90 minutes later. Total locomotor activity, Stereotypic, rearing, and ambulatory behaviors was measured for 90 minutes using a two-frame automated Photobeam Activity Results: Similar to our previous findings, total locomotor activities were higher in female rats after this single cocaine administration. Females had higher levels of phosphorylated PKA substrates after cocaine administration, and this change lasted longer and had a greater magnitude than in cocaine treated male rats. Furthermore, although cocaine administration increased the phosphorylation of ERK proteins, there were no sex differences in p-ERK protein levels either at baseline or after acute cocaine administration. Conclusion: Taken together, these findings suggest that sex differences in basal and cocaine-induced alterations in PKA signaling activity in the NAcc may contribute to sex differences in psychomotor responses to cocaine. However, not all the components of the DA-intracellular signaling pathway maybe heightened in female rats as ERK phosphorylation patterns did not differ between the sexes

Why we should consider sex (and study sex differences) in addiction research

Among mammals, every cell has a biological sex, and the sex of an individual pervades its body and brain. In this review, we describe the processes through which mammals become phenotypically male or female by organizational and activational influences of genes and hormones throughout development. We emphasized that the molecular and cellular changes triggered by sex chromosomes and steroid hormones may generate sex differences in overt physiological functions and behavior, but they may alternatively promote endâ point convergences between males and females. Clinical and preâ clinical evidences suggest that sex and gender differences modulate drug consumption as well as of the transition towards drugâ promoted pathological states such as dependence and addiction. Additionally, sex differences in drug pharmacokinetics and pharmacodynamics will also influence dependence and addiction as well as side effects of drugs. These effects will further interact with socially gendered factors to result in sex differences in the access to, engagement in and efficacy of any therapeutic attempt. Finally, we maintain that â sex samenessâ is as important as â sex differencesâ when building a complete understanding of biology for both males and females and provide a framework with which to classify and guide investigation into the mechanisms mediating sex differences and sex sameness.Sex is a multilayered source of biological bias that promotes multiple physiological divergences and convergences in females and males’ development and activities, including their social and environmental interactions (gender). Current evidence suggests that sex and gender modulate drug consumption and the transition towards drug dependence and addiction as well as the engagement and outcomes of their therapeutic treatment. We provide a framework with which to classify and guide investigation into sex differences and sex sameness in addiction and in other domains of bioâ behavioral research.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/133587/1/adb12382.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/133587/2/adb12382_am.pd

Sex differences in animal models of decision making

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/137573/1/jnr23810.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/137573/2/jnr23810_am.pd

How reward and emotional stimuli induce different reactions across the menstrual cycle

Despite widespread belief that moods are affected by the menstrual cycle, researchers on emotion and reward have not paid much attention to the menstrual cycle until recently. However, recent research has revealed different reactions to emotional stimuli and to rewarding stimuli across the different phases of the menstrual cycle. The current paper reviews the emerging literature on how ovarian hormone fluctuation during the menstrual cycle modulates reactions to emotional stimuli and to reward. Behavioral and neuroimaging studies in humans suggest that estrogen and progesterone have opposing influences. That is, it appears that estrogen enhances reactions to reward, but progesterone counters the facilitative effects of estrogen and decreases reactions to rewards. In contrast, reactions to emotionally arousing stimuli (particularly negative stimuli) appear to be decreased by estrogen but enhanced by progesterone. Potential factors that can modulate the effects of the ovarian hormones (e.g., an inverse quadratic function of hormones’ effects; the structural changes of the hippocampus across the menstrual cycle) are also discussed

Estradiol replacement in ovariectomized rats is antihyperalgesic in the formalin test

A subcutaneous implant of 17 beta-estradiol or progesterone provides steady-state serum hormone levels from 7 to 24 days after implantation and allows the evaluation of the effects of the replacement with these hormones on phase 1 and phase 2 formal in-induced behaviors in ovariectomized (OVX) rats. Graded doses of 17 beta-estradiol (5% to 40%) reduce formalin-induced behavior by 35% to 49% during phase 2 but not during phase 1, as; measured with an automated formalin apparatus. The maximal response is seen with 20% 17 beta-estradiol. The antihyperalgesic effect of 20% 17 beta-estradiol is significant at 8 days after implantation and persists at 21 days. In contrast, graded doses of progesterone have no effect on either phase of formalin. The estrogen receptor antagonist tamoxifen completely prevents the antihyperalgesic effect of the 20% 17 beta-estradiol implant. Formalin-induced behaviors during phase 2 are significantly less in proestrus females and OVX rats given 20% 17 beta-estradiol compared with OVX control rats. Also, the formalin-induced increase in serum corticosterone is attenuated in OVX control rats compared with proestrus females and OVX rats given 20% 17 beta-estradiol. These results indicate that estrogen replacement in OVX rats restores the maximal corticosterone response to tonic pain and, by an estrogen receptor-mediated process, inhibits tonic pain. Pe rspective: Hormone replacement (HR) therapy remains a widely used modality. We used a pharmacokinetically based rat HR model that results in continuous physiological levels of 17 beta-estradiol to demonstrate the analgesic (antihyperalgesic) effects of estrogen replacement in an inflammatory pain model (formalin). These results suggest a potentially important consequence of HR therapy. (C) 2007 by the American Pain Society

Pharmacokinetics and effects of 17 beta-estradiol and progesterone implants in ovariectomized rats

For the pharmacokinetic evaluation of Silastic capsules, ovariectornized (OVX) rats were implanted subcutaneously with this dosage form containing 17 beta-estradiol (5, 10, 15, or 20% in cholesterol, where 5% 17 beta-estradiol equals 0.4 mg) or progesterone (20, 40, 110, or 220 mg of crystalline progesterone). The time-course of serum 17 beta-estradiol and progesterone released from these capsules in the OVX rat is characterized by an initial increase in serum hormone levels followed by a decline and then an apparent steady-state that persists from 7 to 24 days postimplant. Both hormones have large clearance values (total clearance is 97.7 L/day for 17 beta-estradiol and 20.9 L/clay for progesterone). For 17 beta-estradiol and progesterone only, 11% of the dose was released from the implant after 24 days. Thus, the Silastic membrane represents the rate controlling barrier for these hormones. The relationship between graded doses of 17 beta-estradiol or progesterone and serum concentration was linear. Neither tail flick latencies measured at 48, 52.5, and 55 degrees C nor the antinociceptive potency of morphine (ED50 values) were altered by continuous administration to steady-state of graded doses of 17 beta-estradiol or progesterone. We demonstrate how a dose-dependent analysis of some of the behavioral effects of 17 beta-estradiol or progesterone can be conducted at steady-state serum hormone concentrations. Perspective: we describe a method to obtain sustained serum levels of estrogen or progesterone and the consequences of these sustained hormone levels on acute thermal nociception and the antinociceptive response to morphine. This rat model of hormone replacement may provide insights into the role of these hormones in pathological pain states