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Mechanisms of orexin‐induced depolarizations in rat dorsal motor nucleus of vagus neurones in vitro
Author(s) -
Hwang LingLing,
Chen ChiungTong,
Dun Nae J.
Publication year - 2001
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.2001.00511.x
Subject(s) - dorsal motor nucleus , orexin , chemistry , depolarization , excitatory postsynaptic potential , hyperpolarization (physics) , patch clamp , orexin a , biophysics , reversal potential , electrophysiology , membrane potential , endocrinology , medicine , neuroscience , vagus nerve , neuropeptide , receptor , biology , biochemistry , stimulation , stereochemistry , nuclear magnetic resonance spectroscopy
1 Whole‐cell patch‐clamp recordings were made from neurones of the dorsal motor nucleus of the vagus (DMNV), including Fluoro‐gold‐labelled parasympathetic preganglionic neurones (PPNs), in slices of the rat medulla. In the latter case, rats had received an i.p. injection of Fluoro‐gold solution (10 μg) 2‐3 days earlier. 2 Superfusion of orexin A or B (10‐300 n m ) caused a slow depolarization in approximately 30 % of the DMNV neurones, including PPNs. Orexin‐induced depolarizations, which persisted in TTX (0.5 μ m )‐containing Krebs solution, were reduced by 70 % in a low‐Na + (26 m m ) Krebs solution, indicating the involvement of Na + ions. A significant change in orexin‐induced depolarizations was not obtained in either a high‐K + (7 m m ) or Cd 2+ (100 μ m ) Krebs solution. 3 Inclusion of the hydrolysis‐resistant guanine nucleotide GDP‐β‐S in the patch solution significantly reduced the orexin A‐ or B‐induced depolarizations. 4 Under whole‐cell voltage‐clamp conditions, the orexin‐induced inward current declined with hyperpolarization, but did not reverse polarity in the potential range between ‐120 and 0 mV. In low‐Na + solution, the orexin‐induced current was reduced, and the I–V curve reversed polarity at about ‐105 mV; the response was further reduced and the reversal potential shifted to ‐90 mV in a low‐Na + , high‐K + Krebs solution. 5 It is concluded that the peptides orexin A and B, acting on orexin receptors, which are GTP‐binding‐protein coupled, are excitatory to DMNV neurones. In addition, more than one conductance, which may include a non‐selective cation conductance and a K + conductance, appears to be involved in the orexin‐induced depolarization.