A spin label study of the membrane effect of various psychoactive drugs in human erythrocytes

The effect of psychoactive agents with different clinical actions: three sedative neuroleptics (trifluoperazine, alimemazine tartrate, chlorpromazine), an anticholinergic agent (trihexyphenidyl hydrochloride), two tricyclic antidepressants (imipramine, desipramine) and lithium carbonate on the rotational correlation frequency (V+) of the spin label 16NS has been comparatively investigated in whole human erythrocytes. V+ was about 40% increased by the three neuroleptics, the anticholinergic agent and the antidepressant molecules at 0.2 mM. By contrast, lithium did not induce any significant change in V+ at the same concentrations. It can be suggested that the increase in "membrane fluidity", observed with a wide variety of drugs, is a non specific effect, unrelated to the psychotropic action, that can be ascribed to the amphiphilic properties of the tested drugs.