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5‐HT modulates multiple conductances in immature rat rostral ventrolateral medulla neurones in vitro
Author(s) -
Hwang L. L.,
Dun N. J.
Publication year - 1999
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.1469-7793.1999.0217z.x
Subject(s) - chemistry , reversal potential , membrane potential , tetrodotoxin , hyperpolarization (physics) , brainstem , rostral ventrolateral medulla , conductance , biophysics , electrophysiology , patch clamp , 5 ht receptor , endocrinology , neuroscience , medicine , medulla oblongata , central nervous system , serotonin , biology , receptor , biochemistry , stereochemistry , physics , condensed matter physics , nuclear magnetic resonance spectroscopy
1 Whole‐cell patch‐clamp recordings were made from rostral ventrolateral medulla (RVLM) neurones of brainstem slices from 8‐ to 12‐day‐old rats. In the presence of tetrodotoxin (0·5 μM), 5‐HT (50 μM) elicited an outward current (I 5‐HT,outward ) (10/44 neurones) associated with an increase in membrane conductance, and an inward current (I 5‐HT,inward ) (29/44 neurones) accompanied by a decrease or no significant change in membrane conductance. 2 The steady‐state I‐V relationship of I 5‐HT,outward showed an inward rectification; the 5‐HT‐induced current, which reversed at ‐87·9 ± 3·0 mV, was suppressed by 0·1 mM Ba 2+ . 3 Two types of steady‐state I‐V relationship for I 5‐HT,inward were noted: type I I 5‐HT,inward was characterized by a significant decrease in membrane conductance and reversed at a potential close to or negative to the theoretical K + equilibrium potential ( E K ), ‐94 mV, in 8/17 neurones; type II I 5‐HT,inward was not associated with a significant change in membrane conductance and was relatively independent of membrane potential. 4 Both type I and type II I 5‐HT,inward were significantly reduced in a low [Na + ] o solution. In this solution, I 5‐HT,inward decreased with hyperpolarization and had a linear steady‐state I‐V relationship with a reversal potential of approximately ‐110 mV. The reversal potential of type I I 5‐HT,inward shifted to about ‐80 mV as the [K + ] o was increased from 3·1 to 7·0 mM in low [Na + ] o solution. The type II I 5‐HT,inward did not reverse at the estimated E K in the same solution. 5 While not affected by externally applied Cs + (1 mM), I 5‐HT,inward was significantly smaller in RVLM neurones patched with Cs + ‐containing electrodes; the current reversed at ‐11·9 ± 6·4 mV in 8/15 responsive neurones. 6 It may be concluded that in rat RVLM neurones 5‐HT increases an inwardly rectifying K + conductance which may underlie the I 5‐HT,outward and that a combination of varying degrees of K + conductance decrease and a Cs + ‐insensitive, non‐selective cation conductance increase may account for the two types of conductance change associated with I 5‐HT,inward .