Pena F, Neaga E, Amuzescu B, Nitu A, Flonta ML. Amitriptyline has a dual effect on the conductive properties of the epithelial Na channel.
J Pharm Pharmacol 2002;
54:1393-8. [PMID:
12396302 DOI:
10.1211/002235702760345482]
[Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
This study was undertaken with the aim of testing the action of amitriptyline on the epithelial Na channel (ENaC), which belongs to the same family (Deg/ENaC) as ASICs (acid-sensing ion channels) and many other putative members in the brain. We assumed that, having a common protein structure, characterization of the amitriptyline-ENaC interaction could help to elucidate the analgesic mechanism of this tricyclic antidepressant. Na-channel characteristics were derived from the analysis of blocker-induced lorentzian noise produced by amiloride. The effect of amitriptyline, present in the mucosal bathing solution, on the transepithelial short-circuit current (I(sc)) and conductance (G(t)), and on the blocker-induced noise of apical Na channels, was studied on isolated ventral skin of the frog Rana ridibunda. Amitriptyline exerted a dual effect on the macroscopic short-circuit current and conductance of the epithelia, increasing these two parameters in the concentration range 0.1-50 microM, while at higher concentrations (100-1000 microM) it showed an inhibitory action. The decrease in the association rate (k(01)) of amiloride to the apical Na channels from 15.6+/-4.2 microM(-1) s(-1) in control Cl-Ringer to 7.4+/-1.7 microM(-1) s(-1) at 200 microM amitriptyline in a concentration-dependent manner suggests a competitive binding of amitriptyline to the pyrazine ring binding site for amiloride.
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