Emerging data demonstrate that women are more vulnerable on certain aspects of cocaine addiction than are men, suggesting that women and men may require different strategies for the prevention and treatment of cocaine addiction. The primary objective of this project is to understand the mechanistic process by which sex and ovarian hormones influence responding on different aspects and stages of cocaine addiction in order to better understand cocaine addiction in males and females. In addition to dopamine (DA), it has been proposed that the molecular underpinnings of dysregulated glutamatergic signaling may be differentially involved in modulating responding for cocaine, particularly at later stages of addiction (i.e., following chronic excessive use and during cocaine relapse). While there is evidence demonstrating sex and ovarian hormone modulation of mesolimbic DAergic signaling following initial cocaine exposure, very little information is available on sex differences at later stages of addiction or on sex differences in glutamatergic signaling that may cause males and females to respond differently to cocaine. The possibility that the DAergic and glutamatergic processes that mediate responding for cocaine may differ between males and females as a function of stage of addiction is thus a primary focus of this project.
In Aim 1 we will determine the conditions under which sex and hormonal influences are relevant focusing on two behavioral processes that are thought to be critical for maintaining cocaine addiction: cocaine reinforcement and cocaine reinstatement. Cocaine reinforcement will be examined under a progressive-ratio schedule prior to and following extended access self-administration under a 24- hr access discrete trial procedure (4 cocaine infusions/hr, 1.5 mg/kg infusions of cocaine). Cocaine reinstatement will be examined following extended access self-administration under both cocaine-primed and cue-induced conditions.
In Aim 2 the relative contribution of DAergic and glutamatergic signaling in mediating cocaine reinforcement and reinstatement will be determined in both males and females by examining the effects of blockade of D1 and D2 DA receptors and AMPA/kainate and NMDA glutamate receptors in the nucleus accumbens.
In Aim 3 we will determine whether the neuroadaptations that occur in the nucleus accumbens following extended access self-administration are the same or different between males and females focusing on markers of DA (i.e., PKA phosphorylation of tyrosine hydroxylase and DARPP-32) and glutamate (PKA phosphorylation of NR1 and GluR1 subunits of the NMDA and AMPA glutamate receptors) signaling as well as ERK signaling because this pathway requires coincident activation by DA and glutamate receptors. The studies proposed here will expand our understanding of the neurobiological basis of addiction to include the relevant processes in females, and they will provide a much needed foundation for the development of sex-specific pharmacotherapy.
The studies proposed here with both males and females will expand our understanding of the biological basis of addiction to include the biological processes relevant for the development and expression of addiction in females. The implication of studies thus far is that women have an increased biological vulnerability to cocaine's rewarding effects, and the data with regard to estrogen have implications for adolescent females, women cocaine abusers taking birth control pills, and postmenopausal women on estrogen replacement. These studies will provide a much needed foundation for the development of hormonal, pharmacological, and/or molecular based therapeutics for cocaine abuse, especially in women.
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