Noradrenaline inhibits depolarization-induced 3H-serotonin release from slices of rat hippocampus

The depolarization (26 mM K+)-induced release of 3H-serotonin and 3H-noradrenaline from slices of rat hippocampus was studied with a superfusion method. Exogenous NA (in the presence of 10 muM desipramine) inhibited 3H-5-HT release (EC50 3 X 10(-7) M) as well as 3H-NA release (EC50 10(-7) M) by more than 70%. Both of these effects were competitively antagonized by phentolamine, but not by propranolol. It is tentatively suggested that the inhibitory effect of NA on 3H-5-HT release from hippocampus slices reflects the activation of postsynaptic alpha-receptors which are localized on serotonergic nerve terminals.