Effect of systemic blockade of α₁-noradrenergic receptors on sex behavior and vaginal-cervical stimulation-induced Fos in female rats

It is hypothesized that systemic α₁-noradrenergic antagonists may interfere with the transmission of sensory stimulation, particularly vaginal - cervical stimulation (VCS), which is crucial for reproductive functioning. To determine if α₁-noradrenergic transmission receptor activity is necessary for transmission of sensory information important for VCS-dependent events, we conducted an experiment using prazosin, a α₁-noradrenergic receptor antagonist. First, three doses of prazosin (1.0, 0.5 or 0.1 mg/kg) or the 10% ETOH in sesame oil vehicle were administered i.p. and sexual receptivity was assessed 30 min later in ovariectomized, hormone-treated female rats. The 1 mg/kg dose of prazosin significantly inhibited lordosis quotients and lordosis ratings. This dose of prazosin (1.0 mg/kg) was then administered 30 min prior to VCS or control scapular stimulation (CSS) and Fos-IR was examined in the posterodorsal medial amygdala (MeaPD), the medial preoptic area (mPOA), and the rostral ventromedial hypothalamus (rVMH). VCS significantly increased Fos-IR in all of the brain areas examined. Prazosin treatment inhibited the increase in Fos-IR in the mPOA and MeaPD but not in the rVMH. These results suggest that administration of systemic prazosin may selectively affect sensory inputs to the mPOA and MeaPD and these inputs are relevant for the control of female sexual behaviors by peripheral α₁-noradrenergic activity.