[The comparative roles of acetylcholine and noradrenaline in regulation of spontaneous spike activity of cortical neurons].

The effects of acetylcholine and noradrenaline applications on neuronal sponta-neous activity were investigated in slices of guinea-pig parietal cortex. Iontophoretic ejections of both neurotransmitters to the cortical neurons evoked the same-type slowly-developing and long-lasting increase in the rate of spike activity. The different temperature sensitivity of cholinergic and noradrenergic reactions were revealed. During the temperature shift from 32-34 degrees C to 35-36 degrees C the cholinergic effect on neuronal spike activity became extremely strong, that is why even silent at t = 32-32 degrees C neurons became to acetylcholine responsive. Temperature-dependent changes in spike reaction to acetylcholine were accompanied by stable increase in spontaneous spike activity. The noradrenergic reactions did not change with temperature in limits from 32-34 to 35-36 degrees C. In this temperature range spike reactions to glutamate, the main excitation transmitter in the cortex, remained constant. The results obtained suggest that acetylcholine is the main neurotransmitter regulating spontaneous spike activity in cortical neurons.