PARTICIPATION OF PARAVENTRICULAR NUCLEUS OF HYPOTHALAMUS IN CENTRAL REGULATION OF PENILE ERECTION IN THE RAT

Purpose: To investigate the possible participation of the paraventricu lar nucleus of hypothalamus in central regulation of penile erection. Materials and Methods: Male adult Sprague-Dawley rats were anesthetize d and maintained with pentobarbital sodium. The intracavernous pressur e (ICP) was used as an experimental index for penile erection, and was recorded alongside systemic arterial pressure and heart rate. The eff ect on ICP of electrical (30-s train of 30-120 mu A, 40-160 Hz, 1-ms r ectangular pulses) or chemical (L-glutamate, 0.5 nmol/50 nl.) activati on of the paraventricular nucleus of hypothalamus (PVN) or hippocampal formation was evaluated. Results: Electrical activation of the PVN el icited both multiple and single episodes of elevation in ICP, along wi th visible erection and ejaculation. The former pattern exhibited an i ncrease in ICP that was more sustained, with higher peak amplitude and longer latency. Chemical stimulation of neuronal perikarya in the PVN also resulted in similar patterns of rise in ICP and visible erection . These effects were, nonetheless, not accompanied by significant alte rations in systemic arterial pressure and heart rate. Activation of th e hippocampal formation, as we reported previously, similarly elicited multiple and single episodes of increase in ICP. These erectile respo nses, however, were substantially reduced or eliminated upon electroly tic lesion of the ipsilateral PVN. Conclusion: These observations sugg est that the PVN may be an important; nucleus that participates in cen tral neural regulation of penile erection in the rat. Furthermore, an efferent; pathway(s) from the hippocampal formation to PVN may constit ute part of the neural circuitry in the forebrain in the regulation of erectile functions.