Relationship between noradrenalin uptake and secretion by cortical nerve endings in rats during conditioning

The intensity of highly selective uptake (inactivation) of noradrenalin (NA) and of spontaneous and evoked secretion by synaptosomes in the rat cerebral cortex were investigated by the use of ³H]-NA 30 min after defensive conditioning. Changes in the efficiency of adrenergic synaptic transmission during formation and fixation of the temporary connection were judged on the basis of these parameters. Changes in uptake and spontaneous secretion were not observed in the trained and control rats, whereas the intensity of its secretion induced by KC1 (60 mM) was considerably higher in the trained rats than in the controls. An increase in the intensity of evoked secretion was observed only during conditioned reflex formation. It is concluded that conditioning leads to a specific increase in the efficiency of adrenergic synaptic transmission, which is observable in nerve ending isolated 30 min after formation of the reflex.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR. Translated from Neirofiziologiya, Vol. 14, No. 4, pp. 367–372, July–August, 1982.