Paraventricular nucleus of hypothalamus – a brain locus in central neural regulation of penile erection in the rat

Abstract

Keywords: intracavernous pressure, paraventricular nucleus of hypothalamus, penile erection, ratThe approval of sildenafil (Viagra) by the FDA has once again put the subject of male erectile dysfunction (ED) at the forefront of medicine. Over the past decade, a great deal of progress has been made on the study of the physiology of penile erection, mostly on the vascular aspect. However, the issue of central neural regulation of penile erection is relatively less well explored. The paraventricular nucleus of the hypothalamus (PVN) is considered to be an integrative part in the central nervous system for endocrine and autonomic functions, which are speculated to be important mechanisms in the regulation of penile erection. Therefore, we have conducted studies to investigate the role of the PVN in the central regulation of penile erection utilizing the intracavernous pressure (ICP) as an experimental index for penile erection in male adult Sprague-Dawley rats (200±300 g) in an attempt to address part of the issue. The results of our study included the following. 1 Electrical stimulation of the PVN elicited penile erection in terms of a significant increase of ICP. Chemical activation (L-glutamate) of the PVN also induced an increase of ICP. By studying the neural pathways between the hippocampus and the PVN, it can be seen that an electrolytic lesion of the PVN may reduce or eliminate the penile erection-inducing effect from electrical activa-tion of the hippocampus. These observations suggest that the PVN may be a locus in the brain involved in the central regulation of penile erection. In addition, the PVN may be in the efferent neurotransmission pathway from the hippocampus in the regulation of penile erection. 2 Administration of apomorphine (dopamine receptor agonist) into the PVN may also induce a significant increase of ICP through its action on the D2 receptor subtype in the PVN. This observation suggests that PVN may be involved in the central regulation of apomorphine-induced penile erection in the rat. 3 Administration of N-type Ca 2+ channel blocker oconotoxin into the PVN may eliminate the apomorphine-induced penile erection through the PVN. This implies that peripheral administration of apomorphine may activate the PVN through its effect on the Ca 2+ channel in the neurons of the PVN. Based on the above results, it is suggested that the PVN may be an important brain locus that participates in the central neural regulation of penile erection in the rat. Dopaminergic neurotransmission may be one of the pathways in PVN activation-induced penile erection through the Ca 2+ channel in the neurons of the PVN.

The Role of Hypothalamus and Endocrine System in Sexuality.

“…This may contribute to the nitric-oxide production in the PVN and activates oxytocin neurons, thus mediating this sexual response (Melis, Succu, Spano, & Argiolas, 2000). Dopamine neurotransmission to the PVN is also supposed to be involved in penile erection (Chen, 2000). In addition, oxytocin may reduce maternal aggression in a period shortly after the birth, when lactating females show naturally high levels of this behavior (Giovenardi, Padoin, Cadore, & Lucion, 1998).…”