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Functional significance of subtypes of 5-HT receptors in the rat spinal reflex pathway
1Department of Toxicology and Pharmacology, Faculty of Pharmaceutical Sciences, University of Tokyo, Japan.
Abstract:
1. The functional significance of subtypes of 5-hydroxytryptamine (5-HT) receptors was studied in the rat spinal reflex pathway. 2. Ketanserin had no effect on the mono- (MSR) or polysynaptic reflex (PSR) in spinal rats, but decreased the PSR in intact rats. 3. 8-Hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) and 5-methoxy-N,N-dimethyltryptamine (5-MeODMT) decreased the MSR and increased the PSR in spinal rats. 4. Ketanserin antagonized the effects of 5-MeODMT without antagonizing the effects of 8-OH-DPAT. 5. Cinanserin had similar effects to those of ketanserin. 6. These results suggest that both 5-HT1A and 5-HT2 receptors mediate MSR inhibition and PSR augmentation in the spinal reflexes of spinal rats, and that the 5-HT2 receptor has a supraspinal tonic excitatory influence on the PSR in intact rats.