Different effects of reducing agents on omega-conotoxin GVIA inhibition of [3H]-acetylcholine release from rat cortical slices and guinea-pig myenteric plexus.
1. The effect of reducing reagents on omega-conotoxin GVIA (omega-CgTX) inhibition of the release of [3H]-acetylcholine ([3H]-ACh) induced by tityustoxin, K+ 50 mM and electrical stimulation was investigated in rat brain cortical slices. 2. In cortical slices the inhibition of tityustoxin or electrically-stimulated [3H]-ACh release by omega-CgTX was dramatically increased by reducing reagents ascorbate or beta-mercaptoethanol. Dehydroascorbic acid did not substitute for ascorbate. 3. Depolarization induced by K+ 50 mM caused [3H]-ACh release from cortical slices which was not inhibited by omega-CgTX, even in the presence of ascorbate. 4. In the guinea-pig myenteric plexus, omega-CgTX inhibition of the tityustoxin induced release of [3H]-ACh was independent of ascorbate. 5. It is suggested that N-type-like calcium channels in guinea-pigs myenteric plexus may have pharmacological/biochemical diversity from similar channels of rat cerebral cortex.
Casali
T A
TA
Departamento de Farmacologia, ICB-UFMG, Brasil.
Gomez
R S
RS
Moraes-Santos
T
T
Romano-Silva
M A
MA
Prado
M A
MA
Gomez
M V
MV
D000109:Acetylcholine / Q000378:metabolism*; D000818:Animals; D001205:Ascorbic Acid / Q000494:pharmacology; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D002540:Cerebral Cortex / Q000187:drug effects / Q000378:metabolism*; D004558:Electric Stimulation; D004594:Electrophysiology; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008623:Mercaptoethanol / Q000494:pharmacology; D009197:Myenteric Plexus / Q000187:drug effects / Q000378:metabolism*; D009498:Neurotoxins / Q000494:pharmacology; D010455:Peptides / Q000494:pharmacology*; D051381:Rats; D019163:Reducing Agents / Q000494:pharmacology*; D012604:Scorpion Venoms / Q000494:pharmacology; D015222:Sodium Channels / Q000187:drug effects / Q000378:metabolism; D020866:omega-Conotoxin GVIA
D002121:Calcium Channel Blockers; D009498:Neurotoxins; D010455:Peptides; D019163:Reducing Agents; D012604:Scorpion Venoms; D015222:Sodium Channels; C003609:tityustoxin; D008623:Mercaptoethanol; D020866:omega-Conotoxin GVIA; D000109:Acetylcholine; D001205:Ascorbic Acid