[Inhibitory effect of noradrenaline on dopamine release from the hypothalamus of the rat].

1. The release of dopamine from the anterior hypothalamic/preoptic region of the anesthetized and artificially ventilated rats was investigated in vivo using a superfusion technique with a push-pull cannula. L-DOPA and pargyline were added to synthetic cerebrospinal fluid superfusing the area. Dopamine was measured by electrochemical detection after separation by liquid chromatography. Dopamine release rapidly reached stable values after the addition of L-DOPA. 2. Serotonin (10-6M) slightly inhibited dopamine release. Other experiments are necessary to characterize this interaction. 3. Lesions of the ventral noradrenergic bundle by a knife cut significantly increased the release of dopamine. 4. This lesion prolonged the apparent half-life of noradrenaline in the AH/PO. 5. Low concentration (10-7M) of noradrenaline inhibited dopamine release when a lesion was performed prior to the superfusion. 6. These data are compatible with a tonic noradrenergic mechanism mediating an inhibitory control of dopamine release in the AH/PO.