Modifications of the dopaminergic receptors sensitivity and learning of normoxic or hypobaric hypoxic rats.

In the present work we attempted to show whether a modification of the sensitivity of the dopaminergic receptors could act on the learning process in hypobaric hypoxia. Acute treatment with 1 mg/kg-1/day-1 pimozide increases the hypoxia-induced deleterious effect on a conditioned avoidance test whilst chronic administration of pimozide improves behavioral performances in hypoxic rats. Chronic treatment with apomorphine does not modify the learning both in normoxic and hypoxic rats in comparison with control rats, while acute treatment induces an anti-hypoxic protection and a fall in total responses (avoidance + escape). A pimozide-induced hypersensitivity (by chronic treatment) or a direct apomorphine-induced stimulation (by acute treatment) of post-synaptic dopaminergic receptors oppose the deleterious effects of hypobaric hypoxia.