[Effect of neurotropic compounds on the transmembrane potential of synaptosomes]

Using the potential-sensitive dye (3,3-dipropylthiodicarbocyanine) [dis-C3-(5)] it has been shown that synaptosomes isolated from the rat brain cortex by the method of Hajôs retain their transmembrane potential (TMP) close to the K+-diffusional one. In the Krebs-Ringer medium containing 5 mM KCl the TMP of the synaptosomes was equal to 70-80 mV. The cytostatics cytochalazine B and colchicine and the peptides leu- and met-enkephalins and tuftcin in concentrations up to 10(-3) and 10(-4) M did not affect the TMP of the synaptosomes. Cytochalazine B in a concentration of 4 X 10(-4) M and over caused synaptosomal aggregation. The neuroleptics aminazine, trifluoroperazine, haloperidol, the antidepressant imipramine in concentrations about 10(-4) M as well as the tranquilizers diazepam and phenazepam in concentrations about 10(-3) M completely depolarized synaptosomal membranes.