Changes in gene expression within the nucleus accumbens and striatum following sexual experience

Abstract

Sexual experience, like repeated drug use, produces longterm changes including sensitization in the nucleus accumbens and dorsal striatum. To better understand the molecular mechanisms underlying the neuroadaptations following sexual experience, we employed a DNA microarray approach to identify genes differentially expressed between sexually experienced and sexually naïve female hamsters within the nucleus accumbens and dorsal striatum. For 6 weeks, a stimulus male was placed in the home cage of one-half of the hormonally primed, ovariectomized female hamsters. On the seventh week, the two experimental groups were subdivided, with one half paired with a stimulus male. In comparison with sexually naïve animals, sexually experienced hamsters receiving a stimulus male on week 7 exhibited an increase in a large number of genes. Conversely, sexually experienced female hamsters not receiving a stimulus male on week 7 exhibited a reduction in the expression of many genes. For directional changes and the categories of genes regulated by the experimental conditions, data were consistent across the nucleus accumbens and dorsal striatum. However, the specific genes exhibiting changes in expression were disparate. These experiments, among the first to profile genes regulated by female sexual behavior, will provide insight into the mechanisms by which both motivated behaviors and drugs of abuse induce long-term changes in the mesolimbic and nigrostriatal dopamine pathways.

Integrating Neural Circuits Controlling Female Sexual Behavior

“…Still, sexual experience can modify these sexual interactions (Bradley et al, 2005; Meerts et al, 2014). In hamsters this change in copulatory efficiency was tested by giving females different levels of sexual experience and measuring the frequency of intromissions by the male.…”

“…In hamsters this change in copulatory efficiency was tested by giving females different levels of sexual experience and measuring the frequency of intromissions by the male. Giving female hamsters 6 weekly tests (but not 2 tests) for sexual behavior increased the percentage of the male's mounts that included intromission (termed “hit rate”) on the following test (Bradley et al, 2005; Hedges et al, 2009). This was true whether that seventh test was conducted 1 or 6 weeks after the last sexual experience test (Bradley et al, 2005).…”

“…Giving female hamsters 6 weekly tests (but not 2 tests) for sexual behavior increased the percentage of the male's mounts that included intromission (termed “hit rate”) on the following test (Bradley et al, 2005; Hedges et al, 2009). This was true whether that seventh test was conducted 1 or 6 weeks after the last sexual experience test (Bradley et al, 2005). Thus, sexual experience seems to increase the female hamster's ability to regulate intromission by the male (in Berridge's term, increases “wanting”) and these effects of experience are persistent for at least several months without any further experience.…”

Sex, Drugs, and Rock ‘N’ Roll: Hypothesizing Common Mesolimbic Activation as a Function of Reward Gene Polymorphisms

“…Bradley and colleagues (2005) while studying hamsters using microarray analysis found that the sexual experience in either male or female animals differentially up- or down-regulated mRNA expression of a series of genes in the NAc. They found that in comparison with sexually naive animals, sexually experienced hamsters receiving a stimulus male on week seven exhibited an increase in a large number of genes.…”

Natural Reward Experience Alters AMPA and NMDA Receptor Distribution and Function in the Nucleus Accumbens

“…Together, these brain areas mediate naturally rewarding behaviors including feeding [2], [3], [4], [5], drinking [6], maternal behavior [7], social bonding [8], [9] and sexual behavior [10], [11], [12], [13], [14]. Behavioral studies have demonstrated that male rat sexual behavior is rewarding and reinforcing as male rats form a conditioned place preference for copulation [15], [16], [17], develop faster running speeds in T-mazes [18], straight-arm runway [19] or hurdle climbing [20], and perform operant tasks to gain access to sexually receptive females [21], [22].…”