In vitro release of endogenous catecholamines from the neural and intermediate lobe of the hypophysis

This paper shows for the first time that the dopamine present in the neural and intermediate lobe (NIL) of the pituitary gland can be released in vitro by depolarization of the tissue with increased [K+]. The release is Ca++ dependent. This observation is in accordance with the concept that dopamine has a function as a neural transmitter substance in the NIL. At a [Ca++] of 2.5 mM it was also possible to measure the norepinephrine release from the NIL. The dopamine release from the NIL was unaffected by GABA. In contrast, the release of dopamine (but not of norepinephrine) from the medial-basal hypothalamus was enhanced by GABA.