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Updated: Aug 29, 2026

Rapid In Situ Hybridization using Oligonucleotide Probes on Paraformaldehyde-prefixed Brain of Rats with Serotonin Syndrome
Published on: September 23, 2015
Serotonergic depression of spinal monosynaptic transmission is mediated by 5-HT1B receptors
Motoko Honda1, Mitsuo Tanabe, Hideki Ono
1Laboratory of CNS Pharmacology, Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe-dori, Mizuho, Nagoya 467-8603, Japan. honda@phar.nagoya-cu.ac.jp
Abstract:
In the spinal cord, various subtypes of serotonin (5-hydroxytryptamine; 5-HT) receptors are involved in the modulation of motor output. Although the excitatory role of 5-HT(2) receptors is known, the receptor subtypes mediating the inhibitory effect of 5-HT on monosynaptic reflex transmission remain unclear. In this study, segmental spinal reflexes were recorded to examine the receptor subtypes underlying 5-HT-mediated inhibition of monosynaptic reflex transmission in spinalized rats. Under conditions of monoamine oxidase blockade with clorgyline, the 5-HT precursor L-5-hydroxytryptophan depressed the monosynaptic reflex. 3-Hydroxybenzylhydrazine dihydrochloride (NSD-1015), a centrally active decarboxylase inhibitor, abolished this inhibition, confirming that the depression of the monosynaptic reflex by L-5-hydroxytryptophan was due to 5-HT. In the presence of GR127935 or isamoltane, which show high affinity for 5-HT(1B) receptors, L-5-hydroxytryptophan did not suppress the monosynaptic reflex, whereas 5-HT(1A), 5-HT(1D), 5-HT(2) and 5-HT(7) receptor antagonists did not alter the inhibitory effect of L-5-hydroxytryptophan. These results suggest that serotonergic depression of monosynaptic reflex transmission is mediated by 5-HT(1B) receptors.
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