Inhibition of calcium spikes by gamma-amino-butyric acid in the neurons of Lymnaea stagnalis L.
The modulation of action potentials (APs) and high-threshold calcium currents by gamma-aminobutyric acid (GABA) and GABAB receptor agonist baclofen was investigated in identified internally perfused neurons of Lymnaea stagnalis using current-clamp and whole-cell voltage-clamp techniques. GABA (5 x 10(-5) M) and baclofen (5 x 10(-5) M) reversibly reduced overshoot and afterhyperpolarization phase of the action potentials. Application of GABA or baclofen inhibited inward and outward voltage-gated ionic currents. GABA (10(-8)-10(-4) M) was found to suppress high-threshold calcium current in voltage- and dose-dependent manner. These effects were mimicked by baclofen (5 x 10(-5) M) but not by muscimol (5 x 10(-5) M). Inhibition of Ca(2+)-currents could not be prevented by pentylenetetrazole (5 x 10(-5) M) or with pertussis toxin (1 microgram/ml). These results provide evidences for the presence of GABAB receptors in the identified central neurons of Lymnaea stagnalis L.
Rubakhin
S S
SS
Balaton Limnological Research Institute of the Hungarian Academy of Sciences, Tihany, Hungary.
Szücs
A
A
Gurin
V N
VN
Rózsa
K S
KS
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D001418:Baclofen / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D018755:GABA Agonists / Q000494:pharmacology; D017136:Ion Transport / Q000187:drug effects; D008195:Lymnaea / Q000187:drug effects / Q000378:metabolism*; D009118:Muscimol / Q000494:pharmacology; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism*; D010433:Pentylenetetrazole / Q000494:pharmacology; D037342:Pertussis Toxin; D018080:Receptors, GABA-B / Q000187:drug effects / Q000378:metabolism; D010566:Virulence Factors, Bordetella / Q000494:pharmacology; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology*
D018755:GABA Agonists; D018080:Receptors, GABA-B; D010566:Virulence Factors, Bordetella; D009118:Muscimol; D005680:gamma-Aminobutyric Acid; D037342:Pertussis Toxin; D001418:Baclofen; D002118:Calcium; D010433:Pentylenetetrazole