[Electrophysiologic and chemoreceptive characteristics of pontomedullary and thalamic neurons during the process of ontogenetic development].

The background and evoked activity of reticular units in the medulla, pons and ventrobasal complex of the thalamus was studied on cat's fetuses and kittens 54-65 and 1-60 days old, respectively. 63% (pons) and 92% (medulla) of spontaneously active cells were recorded in the fetuses. The highest percentage of evoked responses (60% in the fetuses) was observed upon stimulation of the tongue. Repeated application of stimuli facilitated the firing during the interstimulus intervals, especially during the early developmental stages. Sensitivity to transmitters in the fetuses was maximal to noradrenalin (87%) and glutamate (70%) and minimal to acetylcholine (43%). With development of the animal the number of adrenosensitive units decreased, that of the cholinosensitive increased, and the sensitivity to glutamate remained at the same level. A conclusion is made that the synaptic processes at early developmental stages are mainly of adrenergic and glutamate nature.