Effect of intrathecal capsaicin analogues on the immunofluorescence of peptides and serotonin in the dorsal horn in rats.
The intrathecal administration of capsaicin, a homovanillylamide derivative, has been demonstrated to cause analgesia in response to thermal stimuli. This analgesia has been correlated with a profound depletion of spinal substance P, a putative primary afferent transmitter. We studied the effects of capsaicin, a series of capsaicin analogues, piperine and kainic acid on the immunohistochemical staining of substance P, cholecystokinin, somatostatin, methionine-enkephalin and serotonin. Capsaicin and an analogue 1-nonenoyl-vanillylamide significantly elevated the tail flick latency and when the spinal cords of the rats were analyzed immunohistochemically, a profound depletion of substance P and cholecystokinin was observed. The spinal somatostatin-immunoreactivity of these rats was slightly reduced. Piperine also depleted substance P and reduced somatostatin staining but did not alter the staining intensity or density of cholecystokinin, methionine-enkephalin or serotonin. Kainate-depleted methionine-enkephalin but did not alter any other neuropeptides studied or serotonin. These results may indicate a link between capsaicin-induced analgesia and the concomitant depletion of cholecystokinin and substance P.
D000470:Alkaloids; D000818:Animals; D052117:Benzodioxoles; D002211:Capsaicin / Q000031:analogs & derivatives / Q000494:pharmacology*; D002766:Cholecystokinin / Q000378:metabolism; D004744:Enkephalin, Methionine / Q000378:metabolism; D005231:Fatty Acids, Unsaturated / Q000494:pharmacology*; D005727:Ganglia, Spinal / Q000187:drug effects*; D007608:Kainic Acid / Q000494:pharmacology; D008297:Male; D008856:Microscopy, Fluorescence; D009619:Nociceptors / Q000187:drug effects; D010455:Peptides / Q000378:metabolism*; D010880:Piperidines / Q000494:pharmacology; D053284:Polyunsaturated Alkamides; D051381:Rats; D011919:Rats, Inbred Strains; D012684:Sensory Thresholds; D012701:Serotonin / Q000378:metabolism*; D013004:Somatostatin / Q000378:metabolism; D013373:Substance P / Q000378:metabolism
D000470:Alkaloids; D052117:Benzodioxoles; D005231:Fatty Acids, Unsaturated; D010455:Peptides; D010880:Piperidines; D053284:Polyunsaturated Alkamides; D012701:Serotonin; D013373:Substance P; D013004:Somatostatin; D004744:Enkephalin, Methionine; D002766:Cholecystokinin; D002211:Capsaicin; D007608:Kainic Acid; C008922:piperine