5-HT Modulation of identified segmental premotor interneurons in the lamprey spinal cord.
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.
Biró
Zoltán
Z
Department of Neuroscience, the Nobel Institute for Neurophysiology, Karolinska Institutet, SE 171 77 Stockholm, Sweden.
Hill
Russell H
RH
Grillner
Sten
S
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
D012701:Serotonin