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Microelectrode study on the ionic mechanisms which contribute to the noradrenaline‐induced depolarization in isolated cells of the rabbit portal vein
Author(s) -
Amédée T.,
Large W.A.
Publication year - 1989
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1989.tb12596.x
Subject(s) - depolarization , microelectrode , conductance , biophysics , chemistry , reversal potential , membrane potential , ion , ionic bonding , patch clamp , electrode , biochemistry , biology , combinatorics , receptor , mathematics , organic chemistry
1 Experiments were carried out to determine the identity of the ionic mechanisms which contribute to the noradrenaline‐evoked depolarization recorded with microelectrodes in freshly dispersed rabbit portal vein cells. 2 In normal physiological salt solution with microelectrodes containing 1 m NaCl the reversal potential (E r ) of the noradrenaline‐induced response was −7.6 ± 2.9 mV. When the external NaCl was replaced by equipmolar concentrations of NaI, NaBr and NaNO 3 , E r was −33 ± 3.5 mV, −29.1 ± 5.2 mV and −18.4 ± 1.1 mV, respectively. 3 In physiological salt solution E r of noradrenaline‐evoked responses recorded with electrodes filled with 1 m NaI or 1 m NaNO 3 was + 16.3 + 3.9mV and +10.0 ± 7.6 mV, respectively. These results suggest that an increase in anion conductance contributes to the depolarization to noradrenaline. 4 Data from experiments with organic anions indicated that glutamate behaves as a less permeant anion but that benzenesulphonate blocks the anion conductance to unmask another conductance mechanism activated by noradrenaline. 5 When external NaCl was substituted by choline Cl and Tris Cl E r was −21.3 ± 3.7 mV and −20.5 ± 2.8 mV, respectively. These results suggest that noradrenaline also activates a cation conductance mechanism in freshly dispersed rabbit portal vein cells. It is concluded that the depolarization to noradrenaline recorded with a microelectrode is produced by the simultaneous activation of an anion channel and a separate cation channel.