The suppression of stimulus-evoked release of amino acid neurotransmitters from synaptosomes by verapamil.
Verapamil at 200 microM, prevented the respiratory stimulation, K+ loss, transmitter release, and 45Ca2+ entry into incubated synaptosomes evoked by veratrine (25 to 75 microM) or by high K+ (56 mM). Verapamil (100 microM) also blocked gamma-aminobutyric acid homoexchange, whilst tetrodotoxin was ineffective. Much lower concentrations of verapamil (less than 1 microM) blocked the 45Ca2+ entry caused by veratrine, but not its action in releasing neurotransmitter or K+. It is concluded that verapamil, at 30 to 200 microM, blocks active Na+ channels, thereby preventing depolarization. At greater than 1 microM, verapamil blocks Ca+ channels selectively.
D000596:Amino Acids / Q000378:metabolism*; D000818:Animals; D001224:Aspartic Acid / Q000378:metabolism; D001693:Biological Transport, Active; D002118:Calcium / Q000378:metabolism; D002540:Cerebral Cortex / Q000187:drug effects / Q000378:metabolism*; D005260:Female; D005971:Glutamates / Q000378:metabolism; D018698:Glutamic Acid; D018377:Neurotransmitter Agents / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D013574:Synaptosomes / Q000187:drug effects / Q000378:metabolism*; D013779:Tetrodotoxin / Q000494:pharmacology; D013912:Threonine / Q000378:metabolism; D014700:Verapamil / Q000494:pharmacology*; D014701:Veratridine / Q000494:pharmacology; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
D000596:Amino Acids; D005971:Glutamates; D018377:Neurotransmitter Agents; D013912:Threonine; D001224:Aspartic Acid; D018698:Glutamic Acid; D013779:Tetrodotoxin; D005680:gamma-Aminobutyric Acid; D014701:Veratridine; D014700:Verapamil; D002118:Calcium