The effect of L-tryptophan on spinal cord C-fiber reflexes.
C-fiber reflex were recorded from an ipsilateral S1 ventral root in the acute decerebrate spinal (T10) cat after stimulation of the superficial peroneal nerve. L-Tryptophan, infused in a dose of 150 mg/kg, increased the C-fiber reflex to 210% (S.E.M. +/- 30.1%) of control. This effect was antagonized by cyproheptadine, 0.5 mg/kg. L-Tryptophan increased the C-fiber reflex to 176% (S.E.M. +/- 13.0%) of control after p-chlorophenylalanine pretreatment. Pretreatment of the cats with the decarboxylase inhibitor alpha-methyldopa, 100 mg/kg, 30 minutes before infusion, antagonized the facilitatory effects of L-Tryptophan. L-Tryptophan, 150 mg/kg, had no effect on the monosynaptic or short latency polysynaptic reflexes. 5-Hydroxytryptophan, 20 mg/kg, had erratic effects on the C-fiber reflex producing both facilitation and depression which were not statistically significant. The recovery of tryptamine from brain perfusates, after perfusion of the anterior cerebellum and pons, with a modified Gaddum push-pull cannula, decreased across time. L-Tryptophan caused a slight increase in tryptamine release which was not statistically significant, whereas in cats pretreated with p-chlorophenyl alanine, a significant increase in tryptamine release was seen.
D006916:5-Hydroxytryptophan / Q000494:pharmacology; D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D002262:Carboxy-Lyases / Q000037:antagonists & inhibitors; D002415:Cats; D003533:Cyproheptadine / Q000494:pharmacology; D003655:Decerebrate State; D004558:Electric Stimulation; D005260:Female; D010134:Fenclonine / Q000494:pharmacology; D008297:Male; D008750:Methyldopa / Q000494:pharmacology; D010477:Perfusion; D012018:Reflex / Q000187:drug effects*; D012023:Reflex, Monosynaptic / Q000187:drug effects; D013116:Spinal Cord / Q000502:physiology*; D013126:Spinal Nerve Roots / Q000502:physiology; D013997:Time Factors
D003533:Cyproheptadine; D008750:Methyldopa; D006916:5-Hydroxytryptophan; D002262:Carboxy-Lyases; D010134:Fenclonine