Metabotropic GABA receptors regulate acetylcholine responses on snail neurons.
1. The A type of acetylcholine response of Helix neurons is downmodulated by low concentrations of GABA that do not elicit any measurable change in membrane potential or conductance. 2. We find that these physiological actions are associated with an increase in both intracellular cyclic AMP levels and 45Ca2+ influx. 3. The modulation of the acetylcholine response by GABA is blocked when the neurons are injected with EGTA to prevent a rise in intracellular Ca2+ concentration or when tolbutamide, an inhibitor of protein kinase A, is applied. 4. These results are consistent with the effects of GABA being mediated by a metabotropic GABA receptor that is activated at very low GABA concentrations and mediates modulation of the acetylcholine response via regulation of intracellular Ca2+ and cyclic AMP levels.
Azatian
K V
KV
Biophysics Center, Armenian Academy of Sciences, Yerevan, Armenia.
Ayrapetyan
S N
SN
Carpenter
D O
DO
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism; D006372:Helix, Snails / Q000502:physiology*; D009474:Neurons / Q000502:physiology; D018408:Patch-Clamp Techniques; D018079:Receptors, GABA / Q000502:physiology
D018079:Receptors, GABA; D000242:Cyclic AMP; D000109:Acetylcholine; D002118:Calcium