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Comparison of electrophysiological properties of two types of pre-sympathetic neurons present intermingled in hypothalamic paraventricular nucleus
Yiming Shen1, Seong Kyu Han2, Pan Dong Ryu1,*
1Department of Veterinary Pharmacology, College of Veterinary Medicine and Research Institute of Veterinary Science, Seoul National University, Seoul, Republic of Korea,
2Department of Oral Physiology & Institute of Oral Bioscience, School of Dentistry, Chonbuk National University, Jeonju, Republic of Korea
Correspondence to: Tel: +82-2-880-1254; Fax: +82-2-879-0378; E-mail: pdryu@snu.ac.kr
Received: January 24, 2018; Revised: March 6, 2018; Accepted: March 9, 2018; Published online: April 12, 2018.
The hypothalamic paraventricular nucleus (PVN) contains two types of neurons projecting to either the rostral ventrolateral medulla (PVNRVLM) or the intermediolateral horn (IML) of the spinal cord (PVNIML). These two neuron groups are present intermingled in the same subdivisions of the PVN, and differentially regulate sympathetic outflow. However, the electrophysiological evidence supporting such functional differences is largely lacking. Here, we compared the electrophysiological properties of these neurons by using patch clamp and retrograde tracing techniques. Most neurons in both groups (>70%) spontaneously fired in the cell-attached mode. When compared to the PVNIML neurons, the PVNRVLM neurons showed a lower firing rate with more irregular firing pattern (p<0.05). The PVNRVLM neurons showed smaller resting membrane potential, slower rise and decay times, and greater duration of spontaneous action potentials (p<0.05). The PVNRVLM neurons received greater inhibitory synaptic inputs (frequency, p<0.05) with a shorter rise time (p<0.05). Taken together, the results indicate that two pre-sympathetic neurons differ in their intrinsic and extrinsic electrophysiological properties that may explain the lower firing activity of the PVNRVLM neurons. The greater inhibitory synaptic inputs to the PVNRVLM neurons also imply that these neurons play more integrative roles in regulation of sympathetic activity.
Keywords: rostral ventrolateral medulla, intermediolateral horn of the spinal cord, miniature IPSC, patch clamp technique, spontaneous action potential

© 2018 The Korean Society of Veterinary Science.