Moxidectin interference on sexual behavior, penile erection and hypothalamic GABA levels of male rats.

Programa de Pós-Graduação em Neurociências e Comportamento, Instituto de Psicologia, Universidade de São Paulo, Brazil.
Research in Veterinary Science (Impact Factor: 1.77). 03/2008; 84(1):100-6. DOI: 10.1016/j.rvsc.2007.04.003
Source: PubMed

ABSTRACT The moxidectin (MXD) is an antiparasitic drug used in domestic animals. The mechanism of action, in mammals, involves GABA, a neurotransmitter with an important role in the sexual behavior control. Presently, the effects of 0.2 mg/kg therapeutic dose were studied on sexual behavior, sexual motivation, penile erection and central GABA levels. Sexual behavior results showed increased latencies to the first mount and intromission as well as in inter-intromission interval; a reduction in total mounts was detected on the drug post-treatment. No difference was observed between sexual motivation of control and experimental animals. MXD treatment reduced penile erection and hypothalamic GABA levels. The results suggest that MXD reduced sexual behavior and penile erection by an action on the hypothalamic GABA system. Probably, the lack of effects in the motivational test and the increased mount and intromission latencies as well as decreased total mounts could be explained as a consequence of reduced male rat erection process.

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    ABSTRACT: Doramectin (DOR) is an antiparasitic drug that is widely used in domestic animals. In mammals, DOR act as a γ-aminobutyric acid receptor agonist. This neurotransmitter plays an important role in the regulation of sexual behavior. The present study investigated the effects of two medically relevant doses of DOR on sexual behavior in male rats. We also examined whether previous sexual experience modulates responses to DOR. General activity was first observed in an open field 24, 48, and 72h after administration of 0.1 and 0.3mg/kg DOR to determine the dose and time effects of the drug. Apomorphine-induced penile erection and sexual behavior in inexperienced male rats were then analyzed. The effects of previous sexual experience on subsequent sexual behavior in DOR-treated rats (0.3mg/kg, 24h prior to the test) were also assessed. The standard therapeutic dose (0.2mg/kg) did not modify general activity or penile erection. A slightly concentrated dose of 0.3mg/kg, which is still within the therapeutic range, decreased apomorphine-induced penile erection, whereas 0.2mg/kg did not modify this behavior. Compared with controls, sexual behavior in inexperienced male rats was impaired after 0.3mg/kg DOR. Previous sexual experience had little impact on the effects of 0.3mg/kg DOR. In conclusion, the 0.2mg/kg dose of DOR did not affect motor behavior or apomorphine-induced penile erection. At a more at a slightly higher dose level, the appetitive and consummatory phases of sexual behavior in inexperienced male rats was impaired. Previous sexual experience was unable to reverse this sexual impairment, suggesting that previous sexual experience does not exert a positive effect in attenuating sexual impairment produced by DOR treatment.
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