STRUCTURAL EFFECTS OF N-ARYLCARBAMOYLPYRAZOLINES ON CALCIUM-UPTAKE INRAT-BRAIN SYNAPTOSOMES

N-Arylcarbamoylpyrazolines with various substituents at the para posit ion of the carbamoyl benzene ring inhibited ATP-dependent Ca2+-uptake in synaptosomes prepared from the rat brain. The activity of these com pounds was evaluated as log(1/I-50), the reciprocal logarithm of half inhibitory concentration, I-50 (M), from the concentration-response cu rve for the inhibition of Ca2+-uptake. Among the compounds tested, met hyl methylphenyl)carbamoyl]-2-pyrazoline-4-carboxylate was the most po tent, the I-50 value of which as 9.12 x 10(-7) M. Variations in the ac tivity in terms of log(1/I-50) were quantitatively analysed using a su bstituent parameter, showing that the higher the electron-withdrawing effect of the substituent, the higher was the activity. The substituen t effects were similar to those on insecticidal activity against the A merical cockroach. The higher the inhibitory activity against Ca2+ upt ake, the higher seemed to be the insecticidal activity. Methyl chlorop henyl)carbamoyl]-2-pyrazoline-4-carboxylate had higher inhibitory acti vity against Ca2+-uptake and higher insecticidal activity than the R-i somer, but the difference was greater in the Ca2+-uptake system.