Mechanisms of Serotonergic Facilitation of a Command Neuron

• Published in: Journal of neurophysiology Vol. 98; no. 6; pp. 3494 - 3504
• Main Authors: Antonsen, Brian L, Edwards, Donald H
• Format: Journal Article
• Language: English
• Published: United States Am Phys Soc 01.12.2007
• Subjects: Animals; Astacoidea - physiology; Cambaridae; Cell Membrane - drug effects; Cell Membrane - physiology; Electrophysiology; Escape Reaction - drug effects; Escape Reaction - physiology; Excitatory Postsynaptic Potentials - drug effects; Image Processing, Computer-Assisted; Mechanotransduction, Cellular - drug effects; Microscopy, Confocal; Neurons - drug effects; Neurons, Afferent - drug effects; Serotonin - pharmacology; Synapses - drug effects; Synaptic Transmission - drug effects; Synaptic Transmission - physiology
• ISSN: 0022-3077; 1522-1598
• DOI: 10.1152/jn.00331.2007

Biology Department, Georgia State University, Atlanta, Georgia Submitted 24 March 2007; accepted in final form 26 September 2007 The lateral giant (LG) command neuron of crayfish responds to an attack directed at the abdomen by triggering a single highly stereotyped escape tail flip. Experimentally applied serotonin (5-hydroxytrptamine, 5-HT) can increase or decrease LG's excitability, depending on the concentration, rate, and duration of 5-HT application. Here we describe three physiological mechanisms that mediate serotonergic facilitation of LG. Two processes strengthen electrical coupling between the primary mechanosensory afferent neurons and LG: first, an early increase in the conductance of electrical synapses between primary afferent neurons and LG dendrites and second, an early increase in the membrane resistance of LG dendrites. The increased coupling facilitates LG's synaptic response and it promotes recruitment of weakly excited afferent neurons to contribute to the response. Third, a delayed increase in the membrane resistance of proximal regions of LG increases the cell's input resistance near the initial segment. Together these mechanisms contribute to serotonergic facilitation of LG's response. Address for reprint requests and other correspondence: B. Antonsen, Dept. of Biological Sciences, Marshall University, 1 John Marshall Dr., Huntington, WV 25755 (E-mail: antonsenb{at}marshall.edu )