Serotonin-induced inhibition of locomotor rhythm of the rat isolated spinal cord is mediated by the 5-HT1 receptor class.
The neurotransmitter serotonin (5-HT) induces rhythmic motor patterns (fictive locomotion) of the neonatal rat spinal cord in vitro; this is a useful experimental model to study the generation of a motor programme at exclusively spinal level. Nevertheless, 5-HT slows down the fictive locomotion typically elicited by activation of NMDA glutamate receptors, suggesting a complex action of this monoamine. By means of electrophysiological recordings from multiple ventral roots we demonstrated that the decrease caused by 5-HT in NMDA-induced periodicity was dose-dependent, enhanced after pharmacological blocking of 5-HT2 excitatory receptors, and imitated by pharmacological agonists of the 5-HT1 receptor family. Selective blockers of the 5-HT1A or 5-HT1B/D receptor classes, either alone or in combination, largely (but not completely) attenuated this inhibitory action of 5-HT. It is concluded that the principal inhibitory action of 5-HT on the spinal locomotor network was mediated by certain subtypes of the 5-HT1 receptor class, which tends to oppose the 5-HT2 receptor-mediated excitation of the same network.
Beato
M
M
Biophysics Sector, International School for Advanced Studies (SISSA), Trieste, Italy. beato@sissa.it
Nistri
A
A
D000818:Animals; D000831:Animals, Newborn; D004594:Electrophysiology; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D066298:In Vitro Techniques; D009043:Motor Activity / Q000187:drug effects* / Q000502:physiology; D016202:N-Methylaspartate / Q000494:pharmacology; D010507:Periodicity; D051381:Rats; D017208:Rats, Wistar; D011985:Receptors, Serotonin / Q000187:drug effects / Q000378:metabolism*; D012701:Serotonin / Q000494:pharmacology*; D012702:Serotonin Antagonists / Q000494:pharmacology; D013116:Spinal Cord / Q000187:drug effects* / Q000502:physiology
D018690:Excitatory Amino Acid Agonists; D011985:Receptors, Serotonin; D012702:Serotonin Antagonists; D012701:Serotonin; D016202:N-Methylaspartate