GABA Markers in the Hypothalamus : Topographical Distribution and Origin
A few lines of evidence have been gained over the last few years which suggest that γ-aminobutyric acid (GABA) might be involved as a putative inhibitory transmitter in the hypothalamus, a region much less studied than for instance the substantia nigra where such a function appears firmly established. GABA and its biosynthetic enzyme, glutamate decarboxylase (GAD) have been reported to be concentrated in the hypothalamus (Albers and Brady, 1959; Fahn and Coté, 1968). Hypothalamic slices present a high affinity GABA uptake system (Hökfelt et al., 1970) and a preferential release of physiologically active amino-acids, including GABA, was produced by electrical stimulation of rat hypothalamic synaptosomes (Edwardson et al., 1972). In some hypothalamic nuclei, inhibitory inputs either from an extrinsic or intrinsic origin were mimicked by GABA application and sensitive to picrotoxin and bicuculine, two drugs assumed to be GABA antagonists (Dreifuss and Matthews, 1972; Yagi and Sawaki, 1975). In addition, it has been recently reported that GABA may possibly be involved in the control of the release of hypophysiotropic hormone (Jones et al., 1976; Makara and Stark, 1974; Mioduszewski et al., 1976; Ondo and Pass, 1976; Schally et al., 1977).
KeywordsSubstantia Nigra Kainic Acid Median Eminence Arcuate Nucleus Hypothalamic Nucleus
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