In vivoMicrodialysis of 5-Hydroxyindoleacetic Acid and Glutamic Acid in the Hamster Suprachiasmatic Nuclei

Abstract

SYNOPSIS. The technique of in vivo brain microdialysis rapidly is becoming a popular tool for research on the neurochemical basis of physiological and behavioral functions. The present study describes the application of microdialysis to investigate the endogenous release of 5-hydroxyindoleacetic acid (5-HIAA) and glutamic acid in the suprachiasmatic nuclei (SCN) of hamsters. There were apparent circadian patterns of release of both of these neurosecretions, with peak levels occurring during the dark phase. Pharmacological manipulations of serotonin release and reuptake, using tetrodotoxin and citalopram, respectively, provided evidence that the nocturnal increase in 5-HIAA reflects an increase in serotonergic synaptic activity, rather than intraneuronal metabolism of unreleased serotonin. These results illustrate the usefulness of the microdialysis technique for studies on the neurochemistry of central pacemaker function.