Current responses mediated by endogenous GABAB and GABAC receptors in Xenopus oocytes

Qing Yang, Zhi Wang Li, Jin Bo Wei

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Abstract

The properties of GABA-activated current in Xenopus oocytes and its underlying mechanism were studied using the two-electrode voltage-clamp technique. External application of GABA (10-10∼10-3 mol/L) induced a concentration-dependent outward current in a proportion of oocytes (35.5%, 55/155). Selective GABAA receptor antagonist bicuculline (10-5 mol/L) did not block the GABA-activated current (n = 6). However, 2-hydroxysaclofen (10-4 mol/L), a GABAB receptor antagonist, reversed the GABA-activated outward current to an inward current (n = 9), which was abolished completely by application of I4AA (10-5 mol/L), a GABAC receptor selective antagonist (n = 6). In 20% (12/60) of oocytes, application of baclofen (10-10∼10-4 mol/L), a GABAB receptor agonist, also induced a concentration-dependent outward current 2-Hydroxysaclofen at the concentrations of 3 × 10-6, 3 × 10-5 and 3 × 10-4 mol/L blocked the baclofen (10-5 mol/L)-activated outward current by (6.3 ± 3.2)%, (44.1 ± 2.2)%, and (86.0 ± 1.6)%, respectively (n = 6). The reversal potential for baclofen-activated current was around -96.8 ± 7.2 mV (n = 6), and the baclofen-activated current could be blocked by TEA (n = 5) and Ba2+ (n = 5). These results suggest that there exist endogenous GABA receptors, GABAB receptors mediating a slow and sustained outward current and GABAC receptors mediating an inward current in follicular Xenopus oocytes.

Original languageEnglish (US)
Pages (from-to)311-315
Number of pages5
JournalActa Physiologica Sinica
Volume53
Issue number4
StatePublished - 2001
Externally publishedYes

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Keywords

  • 2-hydroxysaclofen
  • Baclofen
  • GABA receptor
  • GABA receptor
  • I4AA
  • Two-electrode voltage-clamp recording
  • Xenopus oocytes

ASJC Scopus subject areas

  • Physiology

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