Extracellular serotonin in the lateral hypothalamic area is increased during the postejaculatory interval and impairs copulation in male rats.
Serotonin (5-HT) is generally inhibitory to masculine sexual behavior. It has been suggested that 5-HT released after ejaculation may promote the sexual quiescence of the postejaculatory interval (PEI). The following experiments were conducted to test (1) whether extracellular 5-HT increases in either the anterior lateral hypothalamic area (LHAA) or the medial preoptic area (MPOA) of male rats after ejaculation; (2) whether increasing 5-HT in these sites, by microinjecting the selective serotonin reuptake inhibitor alaproclate, could inhibit copulatory abilities; and (3) whether copulation deficits produced by alaproclate were attributable to locomotor impairments. The effects of local application of alaproclate on extracellular 5-HT levels in the LHAA and the MPOA were also tested. Extracellular serotonin was measured in all experiments using in vivo microdialysis. Ejaculation was correlated with enhanced 5-HT release from the LHAA; no 5-HT increases were observed before ejaculation, and levels were decreased toward basal values during a subsequent copulatory series. Elevating 5-HT in the LHAA by microinjecting alaproclate inhibited copulation by increasing the latency to mount, intromit, and ejaculate. This inhibition did not result from nonspecific locomotor impairments. In the MPOA, 5-HT release remained stable throughout copulation, and microinjecting alaproclate into this site did not significantly alter sexual behavior. These data support the large body of evidence suggesting that 5-HT is inhibitory to masculine sexual behavior. Furthermore, the LHAA, but not the MPOA, may be one site responsible for serotonergic inhibition of copulation during the PEI.
Lorrain
D S
DS
Department of Psychology, State University of New York at Buffalo, Buffalo, New York 14260, USA.
Matuszewich
L
L
Friedman
R D
RD
Hull
E M
EM
D000409:Alanine / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D003307:Copulation / Q000187:drug effects / Q000502:physiology*; D004542:Ejaculation / Q000187:drug effects / Q000502:physiology*; D007172:Erectile Dysfunction / Q000503:physiopathology*; D005110:Extracellular Space / Q000737:chemistry; D007031:Hypothalamus / Q000737:chemistry* / Q000378:metabolism / Q000502:physiology; D008124:Locomotion / Q000187:drug effects; D008297:Male; D017551:Microdialysis; D008845:Microinjections; D011301:Preoptic Area / Q000737:chemistry; D051381:Rats; D012701:Serotonin / Q000032:analysis* / Q000378:metabolism; D017367:Selective Serotonin Reuptake Inhibitors / Q000494:pharmacology
D000409:Alanine; D012701:Serotonin; D017367:Selective Serotonin Reuptake Inhibitors; C025293:alaproclate