Cohabitation with receptive females under D2-type agonism in adulthood restores partner preference and brain dimorphism in the SDN-POA following neonatal gonadectomy in male rats.

Perinatal testosterone, or its metabolite estradiol, organize the brain toward a male phenotype. Male rodents with insufficient testosterone during this period fail to display sexual behavior and partner preference for receptive females in adulthood. However, cohabitation with non-reproductive conspecifics under the influence of a D2 agonist facilitates the expression of conditioned partner preference via Pavlovian learning in gonadally intact male rats. In the present experiment, three groups of neonatal PD1 males (N = 12/group) were either gonadectomized (GDX), sham-GDX, or left intact and evaluated for social preferences and sexual behaviors as adults. We then examined whether the effects of GDX could be reversed by conditioning the males via cohabitation with receptive females under the effects of the D2 agonist quinpirole (QNP) or saline, along with the size of some brain regions, such as the sexually dimorphic nucleus of the preoptic area (SDN-POA), suprachiasmatic nucleus (SCN), posterior dorsal medial amygdala (MeApd) and ventromedial hypothalamus (VMH). Results indicated that neonatal GDX resulted in the elimination of male-typical sexual behavior, an increase in same-sex social preference, and a reduction of the area of the SDN-POA. However, GDX-QNP males that underwent exposure to receptive females in adulthood increased their social preference for females and recovered the size in the SDN-POA. Although neonatal GDX impairs sexual behavior and disrupts partner preference and brain dimorphism in adult male rats, Pavlovian conditioning under enhanced D2 agonism ameliorates the effects on social preference and restores brain dimorphism in the SDN-POA without testosterone.

Androgen receptors in Purkinje neurons are modulated by systemic testosterone and sexual training in a region-specific manner in the male rat.

The androgen receptor (AR) is a widely distributed molecule indicating the spread actions of its ligand steroid, and plays an important role underlying male sexual behavior. Nevertheless, the influence of steroid hormones and their receptors on cerebellar neurons, as foundation of sexual behavior, is largely unknown. We sought to determine the influence of peripheral hormones on the AR expression in Purkinje neurons across cerebellar lobules in the vermis of male rats. First, we found a basal AR expression in Purkinje neurons that was higher in the superficial region than the deep region only in cerebellar lobules 2, 4, 5, 7, 8 and 9. Moreover, only the cerebellar lobule 10 showed a significant difference between the coordinates 0.1, 0.3 and 0.9. Second, males with four sessions of sexual training showed a decreased AR density in cerebellar lobules 7, 8, 9 and 10, but not in lobules 2, 4 or 5 when compared to males with one session of sexual training. However, sexual training did not affect AR expression in Purkinje neurons according to their location in any of the cerebellar lobules studied. Third, castration decreased the AR density in the cerebellar lobules 1, 2, 5 and 9 in the superficial region, while in the deep region all cerebellar lobules, except lobule 6, showed a lower AR density after castration. Finally, testosterone replacement restored AR density to control levels in all cerebellar lobules in the superficial region that were affected by castration. Contrary, in the deep region hormonal replacement failed to restore the AR density to control level in the majority of the cerebellar lobules that were affected by castration. Altogether, our findings indicate that Purkinje neurons in the vermis are influenced by systemic testosterone in a region-dependent manner highlighting a link between the cerebellum and gonads in the male rat. The AR function in Purkinje neurons may be related to cerebellar plasticity since both estrogen and progesterone receptors, members of the nuclear receptor family, regulate plasticity processes in Purkinje neurons. We concluded the cerebellum is an important component of the neural circuit for male sexual behavior.

Amino acid tissue levels and GABAA receptor binding in the developing rat cerebellum following status epilepticus.

Incidence of status epilepticus (SE) is higher in children than in adults and SE can be induced in developing rats. The cerebellum can be affected after SE; however, consequences of cerebellar amino acid transmission have been poorly studied. The goal of this study was to determine amino acid tissue concentration and GABA(A) receptor binding in the immature rat cerebellum after an episode of SE. Thirteen-day-old (P13) rat pups received intraperitoneal injections of lithium chloride (3 mEq/kg). Twenty hours later, on P14, SE was induced by subcutaneous injection of pilocarpine hydrochloride (60 mg/kg). Control animals were given an equal volume of saline subcutaneously. Animals were killed 24h after SE induction, the cerebellum was quickly removed, and the vermis and hemispheres were rapidly dissected out on ice. Amino acid tissue concentrations in the vermis and hemispheres were evaluated by HPLC and fluorescent detection. GABA(A) receptor binding in the medial vermis was analyzed by in vitro autoradiography. SE increased the tissue levels of the inhibitory amino acids taurine (80%) and alanine (91%), as well as glutamine (168%) in the cerebellar hemisphere; no changes were observed in the vermis. SE did not modify GABA(A) receptor binding in any cerebellar lobule from the vermis. Our data demonstrate that SE produces region-specific changes in amino acid concentrations in the developing cerebellum.