Transient expression of a novel type of GABA response in rat CA3 hippocampal neurones during development

J Physiol. 1994 Nov 1;480 ( Pt 3)(Pt 3):493-503. doi: 10.1113/jphysiol.1994.sp020378.

Abstract

1. Intracellular recordings were used to study the effects of gamma-aminobutyric acid (GABA) on rat CA3 hippocampal neurones during the first two weeks of postnatal life. 2. In the presence of tetrodotoxin (TTX, 1 microM), from postnatal day 0 (P0) to P12 both associated with an increase in input conductance whereas baclofen (30-100 microM) produced a membrane hyperpolarization. 3. Bicuculline (50 microM) reduced the effects of GABA and abolished the response to isoguvacine without affecting the response to baclofen. 4. This novel bicuculline-insensitive GABA response was chloride dependent and was blocked by picrotoxin (10-100 microM) in an uncompetitive way. In bicuculline and picrotoxin, a GABAB-mediated hyperpolarization appeared. 5. Towards the end of the second postnatal week, bicuculline blocked the GABA-induced depolarization and revealed a small hyperpolarizing response which was blocked by the GABAB antagonist CGP 35348 (0.5-1 mM). 6. It is suggested that, during development, the GABA response was mediated through the conventional GABAA and GABAB receptors as well as a new bicuculline-baclofen-insensitive type of receptor.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aging / physiology*
  • Animals
  • Animals, Newborn / growth & development
  • Animals, Newborn / physiology*
  • Baclofen / pharmacology
  • Bicuculline / pharmacology
  • Hippocampus / cytology
  • Hippocampus / drug effects*
  • Neurons / drug effects*
  • Rats
  • Rats, Wistar
  • Receptors, GABA / drug effects
  • Time Factors
  • gamma-Aminobutyric Acid / pharmacology*

Substances

  • Receptors, GABA
  • gamma-Aminobutyric Acid
  • Baclofen
  • Bicuculline