Spinal cord monoamines modulate the antinociceptive effects of vaginal stimulation in rats.
Perispinal administration (into the lumbar intrathecal space) of phentolamine (40 micrograms), an alpha-adrenergic receptor blocking agent, reduced the analgesic effect of vaginal stimulation by 39.7% (measured by tail flick latency) and 57.1% (measured by vocalization threshold) as compared to controls. Perispinal administration of methysergide (10 micrograms), a serotoninergic receptor blocking agent, reduced the analgesic effect of vaginal stimulation by 48.5% (measured by vocalization threshold), although it did not significantly affect the tail flick measure. In a separate experiment, vaginal stimulation activated the release of norepinephrine and serotonin into a superfusate of the spinal cord. During vaginal stimulation, levels of norepinephrine and serotonin increased about 2-fold above resting levels. These findings indicate that vaginal stimulation releases norepinephrine and serotonin into the spinal cord, thereby exerting an analgesic effect.
D000698:Analgesia; D000818:Animals; D004597:Electroshock; D005260:Female; D008784:Methysergide / Q000494:pharmacology; D009638:Norepinephrine / Q000134:cerebrospinal fluid / Q000378:metabolism*; D059408:Pain Management; D010646:Phentolamine / Q000494:pharmacology; D010812:Physical Stimulation; D051381:Rats; D012701:Serotonin / Q000134:cerebrospinal fluid / Q000378:metabolism*; D013116:Spinal Cord / Q000378:metabolism*; D013623:Tail; D014621:Vagina / Q000502:physiology*; D014828:Vocalization, Animal
D012701:Serotonin; D009638:Norepinephrine; D008784:Methysergide; D010646:Phentolamine