dynamics of responsiveness of cortical neurons towards the repeated combined action of L-glutamate and acetylcholine

The probability, direction, and intensity of changes in mean firing rate of spike activity elicited by application of L-glutamate (Gl) and acetylcholine (ACh) have been compared in a series of successive responses of neuronal units in the sensorimotor cortex of unanesthetized rats; delayed paired application of the above transmitters was used. It is shown that the neurons significantly more often decrease their excitatory responses to the associated action of transmitters, and that responses are not enhanced. In the population of neurons studied, decreases in responsiveness with respect to Gl and ACh occurred with the same probability and in similar fashion over the whole period of testing (60 applications). After long-term transmitter application, potentiation became more typical of the responses to Gl than to ACh.Translated from Neirofiziologiya, Vol. 25, No. 2, pp. 94–97, March–April, 1993.