Interaction of Ca-channel blockers and high pressure at the crustacean neuromuscular junction.
Exposure to high pressure causes a significant depression of synaptic transmission. We examined the effects of various Ca-channel blockers and their interaction with high pressure on excitatory neuromuscular junction currents (EJCs) of lobster abdominal muscles. Reduced [Ca2+]o to half of normal concentration or exposure to 40-60 microM CdCl2, 10-20 microM NiCl2 and 1 microM omega-conotoxin decreased EJCs by 50%. Nifedipine, Nitrendipine and Bay K-8644 were ineffective. Either Ca-blockers or reduced [Ca2+]o, enhanced EJC suppression exerted by high pressure. The data suggest that high pressure primarily affects Ca2+ inflow at the presynaptic terminals through N-type voltage-gated Ca-channel.
Grossman
Y
Y
Department of Physiology, Corob Center for Medical Research, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel.
Colton
J S
JS
Gilman
S C
SC
D000818:Animals; D002104:Cadmium / Q000494:pharmacology; D019256:Cadmium Chloride; D002118:Calcium / Q000494:pharmacology; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D004553:Electric Conductivity / Q000187:drug effects; D066298:In Vitro Techniques; D007700:Kinetics; D008121:Nephropidae; D009469:Neuromuscular Junction / Q000187:drug effects / Q000502:physiology*; D009532:Nickel / Q000494:pharmacology; D010456:Peptides, Cyclic / Q000494:pharmacology; D011312:Pressure; D020960:omega-Conotoxins
D002121:Calcium Channel Blockers; D010456:Peptides, Cyclic; D020960:omega-Conotoxins; D002104:Cadmium; C053423:Conus magus toxin; C022838:nickel chloride; D009532:Nickel; D019256:Cadmium Chloride; D002118:Calcium