title: 5-HT Modulation of identified segmental premotor interneurons in the lamprey spinal cord.
abstract: Ipsilaterally projecting spinal excitatory interneurons (EINs) generate the hemisegmental rhythmic locomotor activity in lamprey, while the commissural interneurons ensure proper left-right alternation. 5-HT is a potent modulator of the locomotor rhythm and is endogenously released from the spinal cord during fictive locomotion. The effect of 5-HT was investigated for three segmental premotor interneuron types: EINs, commissural excitatory and commissural inhibitory interneurons. All three types of interneurons produced chemical postsynaptic potentials in motoneurons, but only those from EINs had an electrical component. The effect of 5-HT was studied on the slow afterhyperpolarization, involved in spike frequency regulation, and on the segmental synaptic transmission to motoneurons. 5-HT induced a reduction in the slow afterhyperpolarization and a depression of synaptic transmission in all three types of segmental interneurons. Thus 5-HT is a very potent modulator of membrane properties and synaptic transmission of last-order segmental premotor interneurons. Such modulation of locomotor network interneurons can partially account for the observed effects of 5-HT on the swimming pattern in lamprey.
authors.affiliation: Department of Neuroscience, the Nobel Institute for Neurophysiology, Karolinska Institutet, SE 171 77 Stockholm, Sweden.
authors.forename: Zoltán
authors.initials: Z
authors.lastname: Biró
authors.forename: Russell H
authors.initials: RH
authors.lastname: Hill
authors.forename: Sten
authors.initials: S
authors.lastname: Grillner
mesh_terms: D000200:Action Potentials / Q000502:physiology; D000818:Animals; D004594:Electrophysiology; D019054:Evoked Potentials, Motor / Q000502:physiology; D006651:Histocytochemistry; D007395:Interneurons / Q000502:physiology*; D007798:Lampreys / Q000502:physiology*; D009046:Motor Neurons / Q000502:physiology*; D012701:Serotonin / Q000502:physiology*; D013116:Spinal Cord / Q000166:cytology / Q000502:physiology*; D009435:Synaptic Transmission / Q000502:physiology
chemical_list: D012701:Serotonin