In vivo monitoring of brain neurotransmitter release for the assessment of neuroendocrine interactions.

1. The neurotransmitter mechanisms regulating neuroendocrine processes have been traditionally inferred from the effects of drugs purportedly acting through specific transmitter systems. The direct appraisal of changes in endogenous neuromediators had to rely initially on analyses of brain samples obtained post-morten. 2. Currently, a more physiological assessment is available through the monitoring ot the extracellular levels of neurotransmitters and their metabolites in discrete brain areas of living animals. Two methodologies, namely in vivo voltammetry and microdialysis, are being increasingly used for this purpose. This article summarizes their principles, relative merits, and limitations and presents some relevant applications. 3. Thus, microdialysis data show a differential response in the amphetamine-induced dopamine release in the nucleus accumbens in adult male and female rats castrated prepuberally. Given their high time-resolution, in vivo electrochemistry techniques seem especially suited for studying the fast, non-genomic effects of steroid hormones. This is illustrated by the voltammetric detection of a rapid release of dopamine in the corpus striatum induced by progesterone in males. 4. These methodologies should be regarded as complementary tools for the assessment of the neurochemical correlates of neuroendocrine interactions.