EFFECTS OF PARAVENTRICULAR LESIONS ON SEX BEHAVIOR AND SEMINAL EMISSION IN MALE RATS

Oxytocinergic neurons of the paraventricular nucleus (PVN) of the hypo thalamus have been implicated in modulating male sexual responses in r ats. Previous investigators have shown that cerebrospinal fluid concen trations of oxytocin (OT) increased after ejaculation and that intrave ntricular administration of OT and electrolytic lesions of the PVN inc reased temporal measures of male sexual behavior. Recently, we have de monstrated that OT-immunoreactive neurons in the parvocellular subnucl ei of the PVN project to lower levels of spinal cord. In the present s tudy, N-methyl-D-aspartic acid lesions, which have been shown to destr oy parvocellular PVN neurons while leaving magnocellular neurons intac t, were used to evaluate the role of parvocellular neurons on male cop ulatory behavior and seminal emissions. OT-immunoreactive fibers were reduced in the lower lumbar spinal cord (L-5-L-6) following N-methyl-D -aspartic acid lesions in the PVN. This reduction was associated with a significant decrease in seminal emission at the time of ejaculation, but mount, intromission and ejaculatory latencies were unaffected. (C ) 1998 Elsevier Science Inc.