Peptidergic control of male sexual behavior: effects of intracerebrally injected substance P and cholecystokinin

Dornan, Wayne Allan (1988) Peptidergic control of male sexual behavior: effects of intracerebrally injected substance P and cholecystokinin. Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

At this point, nothing is known about how peptidergic afferents/efferents of the medial preoptic-anterior hypothalamic continuum (MPOA-AH) participate in the neural control of male rat sexual behavior. In this dissertation an attempt was made to elucidate the roles of substance P(SP) and cholecystokinin (CCK) (two peptides found within the MPOA-AH) in male reproductive behavior. In experiments 1 through 4, a variety of parameters of male copulatory behavior were recorded subsequent to intracerebral injections of SP into the MPOA-AH or the dorsal caudate/putamen (CP). Data from these experiments revealed that bilateral cannulae implanted in the MPOA-AH produced a partial lesion which disrupted the pattern of male copulatory behavior which was dependent on a post-operative test interval. Following the establishment of a new testing interval, a second series of experiments were conducted using a similar approach to that of experiments 1-4. In Experiments 8 and 9, an undiluted SP antiserum (0.3 ul or 2 ul) was injected bilaterally into the MPOA-AH. In Experiment 11, three different doses of CCK-8 (sulphated) were bilaterally injected into the MPOA-AH and the effects on male copulatory behavior following these doses were examined. Bilateral injections of 10, 100, and 200 ng/cannula, of acidified SP into the MPOA-AH significantly reduced the late3ncy to initiate copulation, while the two lower doses also reduced ejaculation latencies. In addition, all three doses of SP significantly reduced the number of mounts while the 100 ng dose also decreased the number of intromissions prior to ejaculation. In contrast to gonadally intact males, MPOA-AH injections of 10 ng of SP in castrated testosterone-deprived animals had no appreciable effect on copulatory behavior. Bilateral injections of 2 ul of a SP antiserum significantly increased mount, intromission, and ejaculations latencies and caused a significant increase in the inter-copulatory interval. In contrast to the MPOA-AH, bilateral injections of SP into the CP had no appreciable effect on male copulatory behavior. Injections of SP into the LV significantly reduced the number of intromissions to ejaculation, while at the same time lengthened both mount latencies and the inter-copulatory interval. CCK-8 injections into the MPOA-AH had no significant effect on any of the parameters of copulatory behavior, although there was a non-significant trend for reduced latencies following the larger doses of CCK-8 compared to saline injected controls. This is the first study to demonstrate that SP, a peptide previously implicated in female sexual behavior, and with a sexually differentiated distribution in the CNS, plays an important role in the neural regulation of male sexual behavior.

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