Release of endogenous catecholamines from slices of hypothalamus of rats

The release of endogenous catecholamines from superfused slices of rat hypothalamus was studied under basal conditions and during release evoked by 40 mM K+. Catecholamines in superfusates, and in extracts of the tissue after stimulation, were isolated by column chromatography and quantitated by liquid chromatography with electrochemical detection. Norepinephrine (NE) was not consistently demonstrable in superfusate collected under basal conditions, but 40 mM K+ caused the release of from 2 to 4 ng/g of tissue per min. The addition of cocaine to the superfusate caused increases in basal and evoked release of NE. Epinephrine (E) could be measured in superfusates of slices from male but not female rats and then only when cocaine was added to the superfusate. Accordingly, the concentration of E in hypothalamus was greater in male rats than in female rats. Dopamine (DA) was not consistently measurable in the spontaneous overflow from slices either in the presence or absence of cocaine. K+-evoked release of DA could be demonstrated in slices from female rats. The addition of cocaine increased the evoked release of DA from slices from both sexes. Corticosterone, added to cocaine, had no effects on the efflux of any of the catecholamines. The experiments suggest that neuronal reuptake of all catecholamines is very efficient in the hypothalamus both under basal conditions and during evoked release.