5-Hydroxytryptamine as a sensitizer of somatic nociceptors for pain-producing substances.
Experiments were performed on loosely restrained, conscious dogs in the femoral artery of which a chronic catheter was implanted. All substances were administered through the catheter and vocalization responses to them were used as a principal measure of nociception. In 10 experiments done on 7 dogs, after a single injection of 3 or 10 mumol of 5-hydroxytryptamine, threshold doses (about 0.5 mumol) of acetylcholine for vocalization produced vocalization responses comparable with those to about 3 times threshold doses. In 5 experiments on 5 dogs, after 10 mumol of 5-hydroxytryptamine, threshold doses (about 0.3 nmol) of bradykinin for vocalization produced vocalization responses comparable with those to about twice threshold doses. These doses of 5-hydroxytryptamine produced small vocalization responses in only 3 of the 12 dogs. These results indicate that 5-hydroxytryptamine, although almost devoid of the activity producing noceceptive responses, sensitizes somatic nociceptors for pain-producing substances.
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D001920:Bradykinin / Q000494:pharmacology; D004285:Dogs; D004357:Drug Synergism; D005260:Female; D008297:Male; D009638:Norepinephrine / Q000494:pharmacology; D010146:Pain / Q000139:chemically induced*; D011955:Receptors, Drug / Q000187:drug effects*; D012701:Serotonin / Q000494:pharmacology*; D014828:Vocalization, Animal / Q000187:drug effects
D011955:Receptors, Drug; D012701:Serotonin; D000109:Acetylcholine; D001920:Bradykinin; D009638:Norepinephrine