Involvement of 5-HT1 and 5-HT5A Receptors in Modulation of Synaptic Transmission and Intrinsic Membrane Properties of Spinal Motoneurons of the Frog (Rana ridibunda)

• Published in: Journal of evolutionary biochemistry and physiology 2022, Vol.58 (1), p.138-148
• Main Authors: Kalinina, N. I., Vesselkin, N. P.
• Format: Article
• Language: English
• Subjects: Action potential; Animal Physiology; Biochemistry; Biomedical and Life Sciences; Dorsal roots; Electrophysiological recording; Evolutionary Biology; Experimental Papers; Intracellular; Latency; Life Sciences; Motor neurons; Potentiation; Rana ridibunda; Receptor mechanisms; Serotonin S1 receptors; Serotonin S5 receptors; Spinal cord; Synaptic transmission
• ISSN: 0022-0930; 1608-3202
• DOI: 10.1134/S0022093022010124

The endogenous monoamine serotonin (5-HT) is involved in the modulation of motor output in vertebrates by interacting with different types of 5-HT receptors. Previously, 5-HT 5A receptors were detected immunohistochemically on rat lumbar motoneurons, supposed to be located postsynaptically. However, we found no information on the presence of 5-HT 5A receptors in the lumbar spinal cord of lower vertebrates, including amphibians. In the present work, we investigated the possible involvement of 5-HT 5A receptors (along with 5-HT 1 receptors) in the modulation of motor output of spinal motoneurons in the frog Rana ridibunda using a pharmacological approach, as well as extracellular and sharp-electrode intracellular recording of potentials. The results of extracellular recordings using the application of 5-CT, a 5-HT 1 and 5-HT 5A receptor agonist, and SB-699551, a selective 5-HT 5A receptor antagonist, indicate a spatiotemporal modulation of the activity of ventral horn neurons. Changes in the amplitude of the antidromic field potential, peak amplitude of the evoked root potential and intracellular dorsal root postsynaptic potential, as well as 5-CT-induced changes in the frequency of extracellular spikes and latency of the first intracellular action potential (AP), were time-dependent: potentiation occurred within the first minutes and was later followed by depression. Taken together, our results indicate the involvement of 5-HT 5A receptors, along with 5-HT 1 receptors, in the modulation of motor output of frog spinal motoneurons.