To examine whether the actions of nitric oxide (NO) were critical to the apomorphine-generated genital vasocongestive arousal (GVA) responses in both intact and ovariectomized (OVX) young adult female rats. We also investigated whether the diminished GVA responses in aged rats could be restored using an antihypertensive treatment.

In female Wistar rats (n=8), apomorphine- induced GVA responses were assessed following various treatments. Young adult females were ovariectomized or treated with the NO synthase (NOS) inhibitor Nnitro-L-arginine methyl ester (30mg/kg, i.v.) followed by an NO-mimetic, sodium nitroprusside (10mg/kg/min, i.v.). Aged females (18 months-old; n=8) were treated for 2 weeks with the angiotensin converting enzyme inhibitor (ACEI) enalapril (30mg/kg per day, p.o.) + low sodium

(0.04%).

Age-associated reduction in sexual responses in normotensive rats was greatly enhanced by brief, aggressive antihypertensive treatment. The enhanced vasocongestive responses persisted for 5 weeks off-treatment. Both OVX and NOS inhibition significantly decreased sexual responses in the young female rats. Systemic administration of an NO-mimetic recovered vasocongestive responses in the NOS blocked rats, but not in OVX animals.

Brief aggressive ACEI treatment markedly improved sexual responses in aged female rats, and systemic delivery of a NO-mimetic recovered sexual responses in globally NOS blocked animals.