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Differential regulation of 5‐hydroxytryptamine release by GABA A and GABA B receptors in midbrain raphe nuclei and forebrain of rats
Author(s) -
Tao Rui,
Ma Zhiyuan,
Auerbach Sidney B.
Publication year - 1996
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1996.tb16049.x
Subject(s) - dorsal raphe nucleus , median raphe nucleus , nucleus accumbens , bicuculline , chemistry , raphe nuclei , muscimol , gabab receptor , endocrinology , medicine , gabaa receptor , receptor , biology , serotonin , serotonergic , biochemistry
1 Extracellular 5‐hydroxytryptamine (5‐HT) was determined in dorsal raphe nucleus (DRN), median raphe nucleus (MRN) and nucleus accumbens by use of microdialysis in unanaesthetized rats. 2 Infusion of the γ‐aminobutyric acid (GABA) A receptor agonist muscimol into DRN and MRN resulted in decreased 5‐HT in DRN and MRN, respectively. Muscimol infusion into nucleus accumbens had no effect on 5‐HT. 3 Infusion of the GABA A receptor antgonist bicuculline into DRN resulted in increased DRN and nucleus accumbens 5‐HT. Bicuculline infusion into MRN had no effect on 5‐HT. This suggests that endogenous GABA had a tonic, GABA A receptor‐mediated inhibitory effect on 5‐HT in DRN, but not in MRN. 4 Infusion of the GABA B receptor agonist baclofen into DRN produced a decrease in DRN 5‐HT. Baclofen infusion into nucleus accumbens resulted in decreased nucleus accumbens 5‐HT. This suggests that GABA B receptors are present in the area of cell bodies and terminals of 5‐hydroxytryptaminergic neurones. 5 Infusion of the GABA B receptor antagonists phaclofen and 2‐hydroxysaclofen had no effect on midbrain raphe and forebrain 5‐HT. This suggests that GABA B receptors did not contribute to tonic inhibition of 5‐HT release. 6 In conclusion, 5‐HT release is physiologically regulated by distinct subtypes of GABA receptors in presynaptic and postsynaptic sites.