Dopaminergic modulation of the septo-hippocampal cholinergic system activity under stress

The effects of the dopaminergic agonist apomorphine or the antagonist sulpiride on high affinity choline uptake and newly synthesized acetylcholine release by hippocampal synaptosomal preparations, were examined in rats subjected to immobilization stress. Increased dopamine uptake by septal synaptosomal preparations was taken as evidence for increased mesoseptal dopaminergic activity in response to stress. While apomorphine treatment failed to alter choline uptake or acetylcholine release in unhandled rats, it did however prevent the stress-induced increase in these cholinergic parameters. In contrast, after treatment with sulpiride both choline uptake and acetylcholine release were increased in unhandled rats, as they were after acute stress. Acute stress of sulpiride treated rats however resulted in changes similar to those produced by administration of either sulpiride or stress separately. We conclude that the mesoseptal dopaminergic system plays an important role in modulating the activity of the septo-hippocampal cholinergic system under stress.