[Effect of enkephalins and morphine on the neurons of the midbrain reticular formation]

It has been established in experiments on conscious cats that variation in spontaneous activity of the midbrain reticular formation neurones in response to microiontophoretic application of morphine largely coincides with the pattern of changes in impulsation in response to administration of leu-enkephalin rather than to met-enkephalin. Concurrent application of the subthreshold dose of enkephalins and morphine has revealed a possibility of the effects summation, the highest pharmacological activity being exhibited by leu-enkephalin combined with morphine. Selective blocking by enkephalins and morphine has been observed of evoked neuronal responses to peripheral exposures (ECS, stimulation of the sciatic nerve). Meanwhile the responses of cortical origin have been found to remain unchanged.