Criteria for intracellular identification of pre-sympathetic neurons in the rostral ventrolateral medulla in the rat.
Previous studies revealed that a relatively small group of reticulospinal neurons located in the rostral ventrolateral medulla (RVLM) plays a key role in the generation of resting vasomotor tone and in reflex control of arterial blood pressure. These medullary pre-sympathetic neurons have been extensively studied with extracellular microelectrodes, but so far few attempts have been made to examine their intracellular properties in vivo. This report, based on intracellular recordings from 8 RVLM pre-sympathetic neurons in anaesthetised rats, sets out criteria for intracellular identification of such neurons. We propose that two features are sufficient to classify RVLM neurons as pre-sympathetic during intracellular recording: inhibitory response to stimulation of the aortic depressor nerve with short bursts of pulses applied at low frequency; and antidromic stimulation from the upper thoracic segments. Cardiac oscillations in the membrane potential or responses during large changes in blood pressure can be due to movement artefact, and are therefore not reliable as a means of demonstrating baroreceptor input. Further intracellular studies of these neurons will undoubtedly result in further progress in understanding their function.
Lipski
J
J
Department of Physiology, School of Medicine, University of Auckland, New Zealand.
Kanjhan
R
R
Kruszewska
B
B
Rong
W F
WF
D000818:Animals; D001794:Blood Pressure / Q000502:physiology; D004558:Electric Stimulation; D004594:Electrophysiology; D007424:Intracellular Fluid / Q000502:physiology; D008297:Male; D008526:Medulla Oblongata / Q000166:cytology* / Q000502:physiology; D009474:Neurons / Q000166:cytology* / Q000502:physiology; D011311:Pressoreceptors / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D013564:Sympathetic Nervous System / Q000166:cytology* / Q000502:physiology