PARTICIPATION OF HIPPOCAMPAL-FORMATION IN NEGATIVE FEEDBACK INHIBITION OF PENILE ERECTION IN THE RAT

Detailed information on how the central nervous system regulates penil e erection, particularly the inhibitory aspect, is sparse. We observed in Sprague-Dawley rats anesthetized and maintained with chloral hydra te that administration of papaverine (400 mu g) directly into the corp ora cavernosum of the penis produced an increase in intracavernous pre ssure (ICP). This elicited experimental index for penile erection was accompanied by a transient increase in the root mean square values, co ncurrent with a shift in the contribution of Theta (increase) and delt a (decrease) power to the hippocampal electroencephalographic (hEEG) a ctivity. Reversal blockade of these hEEG responses with xylocaine, giv en either intrathecally at the L6-S1 spinal levels or unilaterally to the hippocampal formation, significantly heightened and prolonged the ICP response. Pretreatment with xylocaine by itself, however, did not alter appreciably the baseline ICP or hEEG activity. These results sug gest the presence of a novel negative feedback inhibitory mechanism in the hippocampal formation, which is triggered by ascending sensory in puts initiated by tumescence of the penis during normal erectile proce sses. (C) 1998 Elsevier Science B.V.