[Mikroiontophoretic analysis of the interrelation between spike activity and chemical sensitivity of neurons of the medial thalamus to acetylcholine and noradrenaline in alert rats].

An interconnection between spontaneous impulse activity of medial thalamus (MT) neurones and their chemical sensitivity to acetylcholine (ACh) and noradrenaline (NA) was revealed in rats by means of microelectrode recording and microionophoresis in conditions of free behaviour and during immobilization stress. The neurones with the most rare reactions (inhibitory to ACh and excitatory to NA) had higher frequency and variance of discharges in comparison to the cells with most typical responses (excitatory to ACh and inhibitory to NA). The number of cases with changed sensitivity of single units in these conditions directly correlated with the firing rate and variance of the unit discharges. Qualitative changes in cells' sensitivity to ACh and NA elicited in rats both "spontaneously" in conditions of immobilization stress and under the action of electrocutaneous stimulation were not always tightly connected with the observed phasic changes of their discharges.