| Abstract: | The effect of penicillin on the membrane potential (MP) and synaptic activity of motoneurons in the isolated spinal cord of the river lamprey was investigated. In cells with a low initial MP (58.7±5.2 mV, n=28), penicillin (2.5 mmole·liter–1) caused a depolarization, and potentiated excitatory postsynaptic potentials (EPSPs) that were evoked by stimulating spinal tracts and dorsal roots. The EPSPs were potentiated by 80–220% relative to their initial amplitude. In motoneurons with a higher MP (72.0±5.7 mV, n=20), a depolarization did not develop, and the potentiation of EPSPs did not exceed 25–70%. The effects of penicillin were inhibited when antagonists of excitatory and inhibitory amino acids were added to the superfusate. The results obtained imply that the motoneuron membranes have two acceptor sites for penicillin.Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, Saint Petersburg Institute of Biological Research, Belgrade, Yugoslavia. Translated from Neirofiziologiya, Vol. 24, No. 2, pp. 151–160, March–April, 1992. |
