GABAA receptor-mediated K(+)-evoked GABA release from globus pallidus--analysis using microdialysis.
Presynaptic modulation of gamma-aminobutyric acid (GABA) release in the globus pallidus of rat was examined using in vivo microdialysis procedures. The addition of nipecotic acid (0.5 mM), a neuronal GABA uptake inhibitor, into perfusate, resulted in an increase in the basal GABA released from the globus pallidus. GABA release from the globus pallidus was also augmented dose-dependently by the addition of KCI. Muscimol, a GABAA receptor agonist, caused a significant suppression of the high potassium (100 mM)-evoked release of GABA, and this suppressive effect of muscimol was antagonized invariably by bicuculline, a GABAA receptor antagonist. On the other hand, baclofen, a GABAB receptor agonist, did not induce any significant changes in the 100 mM KCl-evoked GABA release. Similarly, 3-aminopropylphosphonous acid, a GABAB receptor agonist, failed to suppress the GABA release induced by high (100 mM) and low (50 mM) concentrations of KCl from the globus pallidus. Furthermore, CGP 54626A,-a GABAB receptor antagonist, had no significant effect on these KCl-evoked GABA releases. These results suggest that presynaptic modulation of GABA release in the globus pallidus may be mediated by the GABAA autoreceptor.
Hashimoto
T
T
Department of Pharmacology, Kyoto Prefectural University of Medicine Kawaramachi Hirokoji, Japan.
Kuriyama
K
K
D000818:Animals; D001418:Baclofen / Q000494:pharmacology; D015226:Dinucleoside Phosphates / Q000494:pharmacology; D018755:GABA Agonists / Q000494:pharmacology; D005917:Globus Pallidus / Q000378:metabolism*; D008297:Male; D017551:Microdialysis; D009118:Muscimol / Q000494:pharmacology; D009557:Nipecotic Acids / Q000378:metabolism; D011189:Potassium Chloride / Q000494:pharmacology*; D011392:Proline / Q000031:analogs & derivatives*; D051381:Rats; D017208:Rats, Wistar; D011963:Receptors, GABA-A / Q000378:metabolism*; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
D015226:Dinucleoside Phosphates; D018755:GABA Agonists; D009557:Nipecotic Acids; D011963:Receptors, GABA-A; C012276:diadenosine pyrophosphate; C030278:nipecotic acid; D009118:Muscimol; D005680:gamma-Aminobutyric Acid; D011189:Potassium Chloride; D011392:Proline; C010983:homoproline; D001418:Baclofen