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FURTHER ANALYSIS OF INHIBITORY EFFECTS OF PROPRANOLOL AND LOCAL ANAESTHETICS ON THE CALCIUM CURRENT IN Helix NEURONES
Author(s) -
AKAIKE N.,
ITO H.,
NISHI K.,
OYAMA Y.
Publication year - 1982
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.1476-5381.1982.tb09188.x
Subject(s) - propranolol , procaine , inhibitory postsynaptic potential , chemistry , biophysics , pipette , membrane potential , voltage clamp , membrane , pharmacology , biochemistry , endocrinology , biology
1 The effects of propranolol and local anaesthetics on Ca 2+ current (I Ca ), individually separated from other ionic currents, in Helix neurones were studied under voltage clamp, using a suction pipette technique. 2 Increases in external Ca 2+ concentrations overcame the inhibitory action of propranolol on lea‐Double reciprocal plots for peak I Ca versus external Ca 2+ concentrations in the presence or absence of propranolol did not intersect at the ordinate. 3 Internal application of propranolol (10 −4 m ) inhibited I Ca to about 40–60% of the control in a time‐dependent manner. 4 Lignocaine and procaine at concentrations of 10 −3 –10 −2 m inhibited I Ca without shifting the threshold in the I‐V relationships. Internal application of lignocaine (10 −3 –10 −2 m ) also inhibited I Ca : the ratio of depression of the I Ca was almost equivalent to that of the agent applied externally. 5 The results provide evidence that propranolol inhibits I Ca in a noncompetitive manner with Ca 2+ at the cell membrane, and suggest that the agents may occupy the receptor site in the Ca 2+ ‐channel somewhere between the outer surface and inner phase of the membrane.