RAT MODEL FOR THE STUDY OF PENILE ERECTION - PHARMACOLOGICAL AND ELECTRICAL-STIMULATION PARAMETERS

We report the use of a modified rat model for the study of the mechani sms of penile erection. In 92 Sprague-Dawley rats, the cavernous nerve was stimulated with different pulse intensities and frequencies, and the intracavernous pressure, time to maximal pressure and total durati on of tumescence were measured. A maximal response was elicited at 20 pulses per second (pps) and 1.5 mA. Using this as 100%, we determined the relative pressure responses obtained with other frequencies: 5 pps , 57.3% (p = 0.007), 10 pps, 84.9% (p = 0.043); 30 pps, 99.5% (p = 0.8 32); 40 pps, 97.8% (p = 0.168); 50 pps, 90.9% (p = 0.02 1); 100 pps, 7 6. 1 % (p < 0.00 1). The time to maximal pressure varied with differen t frequencies, but was in all cases significantly different from the 2 0-pps response. Erection time during continuous cavernous nerve stimul ation was significantly longer with frequencies below 20 pps (10 and 5 pps). In 30 rats, the physiologic response to intracavernous injectio n (0.03 ml) of acetylcholine, atropine, guanethidine, norepinephrine, phenylephrine, papaverine, terbutaline (intravenous also) and phentola mine was measured. Papaverine caused a dose-dependent rise in pressure ; acetylcholine, atropine (a parasympathetic blocking agent) and guane thidine all had minimal effects. Phentolamine and norepinephrine incre ased systemic blood pressure, whereas phenylephrine decreased the intr acavernous pressure in response to electrostimulation significantly. T his study confirms the feasibility of this inexpensive, readily availa ble model and defines the optimal parameters for studies of electrical stimulation of the cavernous nerve and intracavernous pharmacologic a gents, allowing neurophysiologic studies of erection.