Selegiline enhances erectile activity induced by dopamine injection in the paraventricular nucleus of the hypothalamus in anesthetized rats

Apomorphine delivered in the paraventricular nucleus of the hypothalamus (PVN) induces penile erection in rats, suggesting a role of dopaminergic projection to the PVN in the control of penile erection. We assessed whether the selective inhibitor of monoamine oxidase B, selegiline, could enhance the erectile activity induced by dopamine delivery in the PVN. Intracavernous and blood pressure (ICP and BP) were monitored in anesthetized rats to quantify ICP rises (number and percentage of ICP maximum/mean BP (ICPmax/BP × 100)) elicited by 10 μg dopamine injection in the PVN after saline or 3 mg/kg i.v. selegiline (8 rats per group). The number of ICP rises (mean ± s.d.: 4.5 ± 2.9 vs 1.4 ± 1.9; P = 0.017) and their ICPmax/BP × 100 (49 ± 8% vs 34 ± 9%; P=0.015) were significantly greater upon dopamine injection in the PVN than upon vehicle. Compared to saline i.v., 3 mg/kg selegiline pretreatment significantly increased the number of ICP rises induced by dopamine injection in the PVN (9.4 ± 2.6 vs 4.5 ± 2.9; P < 0.001), without affecting their amplitude. This suggests that drugs potentiating dopaminergic responses in the central nervous system might enhance proerectile commands of supraspinal origin.