[The effect of electrical stimulation of the locus coeruleus on the neuronal activity of the parietal associative cortex].

In experiments performed on cats operated under ketamine anaesthesia and subsequently immobilized by myorelaxin it was demonstrated that locus coeruleus (LC) being stimulated by a train of pulses can exert influence on 79% of parietal cortex neurons. Inhibition of the background activity for 300-700 ms or a decrease in its frequency by 16-32% were observed in them after the LC stimulation. During intracellular recording neurons with background activity and "silent" neurons responded to LC stimulation by hyperpolarization (5-7 mV) lasting for 120-500 ms with latency of 30-90 ms. The duration of the inhibitory pause in background activity caused by transcallosal stimulation increased by 50-200 ms due to conditioning stimulation of LC. The duration of IPSPs evoked by transcallosal stimulation also increased by 50-100 ms under the influence of LC stimulation. It is concluded that the influence of LC stimulation on the activity of the parietal cortex neurons can be exerted either directly as inhibition of background activity and hyperpolarization or as modulation of effects of other neurotransmitters.