The activation of γ aminobutyric acid A receptors in the paraventricular nucleus of the hypothalamus reduces non-contact penile erections in male rats

Abstract

Male rats show 4–6 penile erection episodes when put in the presence of an inaccessible receptive female. These non-contact penile erections were reduced dose-dependently by muscimol, a γ aminobutyric acid (GABA) A receptor agonist, when given into the paraventricular nucleus of the hypothalamus (0.1, 0.5, 1 and 2 μg). In contrast, baclofen, a GABA B receptor agonist (2 μg) was ineffective. Muscimol reduction of non-contact penile erections was not seen when male rats were pretreated with bicuculline methiodide (2 μg) given 5 min before muscimol into the paraventricular nucleus. Since muscimol injected into the paraventricular nucleus also prevents penile erection induced by drugs (e.g. apomorphine, oxytocin or N-methyl- d-aspartic acid), the present results show that an increased GABAergic activity in the paraventricular nucleus can impair the expression of penile erection induced not only by drugs but also by sexual physiological stimuli.