In vivo release of neurotransmitters in the medial basal hypothalamus of the monkey.

In vivo release rates of norepinephrine (NE), epinephrine (E), dopamine (DA), gamma-aminobutyric acid (GABA), glutamate (GLU) and beta-endorphin (beta E) in the medial basal hypothalamus (MBH) of unanaesthetized female macaca fascicularis monkey, and the effects thereon of estrogen (E2) treatment, have been estimated using push-pull perfusion methodology. DA, NE, E, GABA, GLU and beta E were all detectable in 30 min perfusate fractions. No direct correlation between their release rates and those of LH and PRL could be observed. E2 induced an initial decrease, then an increase, in LH and PRL secretion, and concomitant changes in the release patterns of DA, NE, E. GABA and GLU were apparent. This study demonstrates that in vivo push-pull perfusion methodology may be applied to the unanaesthetized monkey, and when combined with venous catheterization for serial blood sampling may prove to be a powerful tool in the investigation of the central molecular events governing neuroendocrine functions.