It is well established that the neurotransmitter
serotonin participates in the control of sexual behaviour in
the male rat. Recently, it has been found that serotonergic
activity may either inhibit or facilitate sexual behaviour,
depending on the subtypes of serotonin receptors involved.
However, the participation of 5-HT2 receptors in the control
of male rat copulation has received little experimental
attention, and the published data are equivocal.
In Experiments 1-4, it was established that the 5-
HT2/1C agonist DCI inhibits sexual behaviour in male rats;
this inhibition is effectively reversed by the antagonists
ritanserin, pirenperone, and ketanserin. Comparison of these
effects , with reference to the binding profiles of each
drug, provided strong evidence that 5-HT2/1C receptors
mediate an inhibitory influence on sexual behaviour in male
rats. In addition, a tentative claim may be made that the
effects of these drugs may be more attributable to 5-HT2
activity than 5-UT1C activity.
‘Wet dog shake’ behaviour in rats is known to be 5-HT2-
dependent. Experiments 5—7 evaluated the novel proposition
that the incidence of spontaneous wet dog shaking (WDS) by
male rats in mating tests may provide a behavioural assay of
concurrent 5—HT2 activity. WDS was found to be associated with copulatory inhibition in noncopulating males, compared
to normal copulators, and this relationship was specific to
mating situations. Activating 5-HT2/1C receptors with DOl
simultaneously induced WDS and inhibited copulation. Thus,
the incidence of spontaneous WDS in untreated males may
reflect the function of a 5—HT2—mediated neural mechanism
that tonically inhibits copulation in male rats. In
Experiment 8, DOl microinjection in the nucleus raphe
obscurus/inferior olivary complex also induced WDS and
inhibited copulation. This suggests that the hypothesized 5-
flT2-dependent inhibitory mechanism is vested in the
ventromedial brainstem. Recent anatomical findings support
this suggestion: cells in this region have bifurcating
axons, projecting collaterally to both the medial preoptic
area (implicated in sexual behaviour) and to the ventral
cervical spinal cord (implicated in WDS). Overall, the
results of the eight experiments provide strong evidence
that 5-HT2 receptors mediate some of the inhibitory effects
of serotonin on male rat sexual behaviour.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:BVAU.2429/6967 |
| Date | 05 1900 |
| Creators | Watson, Neil Verne |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Relation | UBC Retrospective Theses Digitization Project [http://www.library.ubc.ca/archives/retro_theses/] |
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