| Abstract: | In chronic experiments on cats, the effects were investigated of iontophoretic application of the adrenomimetic ephedrine and the  -blocker obsidan (propranolol) on neuronal response induced in the motor cortex by conditioned stimulus presentation during performances of instrumental lever-pressing response. Inhibition of background firing activity and response in most neurons induced by conditioned stimuli was produced by ephedrine, whereas obsidan application enhanced this activity. It was concluded that steady, tonic inhibitory action of the noradrenergic system on background and induced firing activity in cortical neurons takes place during free-ranging behavior. Temporary reinforcement of noradrenergic influences could be an important element in mechanisms of external inhibition during stressful situations, aversive effects, and distractive stimuli.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 22, No. 5, pp. 680–688, September–October, 1990. |
