A role for Q type Ca2+ channels in neurotransmission in the rat urinary bladder.
1. In isolated bladder strips of the rat, a substantial component (46%) of the Ca(2+)-dependent contractile response to electrical field stimulation (5 Hz) was resistant to combined block of both N and P type Ca2+ channels by omega-conotoxin-GVIA (300 nM) and omega-agatoxin-IVA (100 nM) respectively. 2. The resistant portion (non-N, non-P) was sensitive to omega-conotoxin-MVIIC (3 microM), which in addition to N and P also blocks Q type channels at this concentration. omega-Conotoxin-MVIIC administered alone, inhibited the neurogenic response to the same degree as that observed in the combined presence of omega-agatoxin-IVA, omega-conotoxin-GVIA and omega-conotoxin-MVIIC. 3. omega-Agatoxin-IVA (100 nM), a concentration that fully inhibits P type channels, had a negligible effect on the neurogenic response. Following blockade of N type Ca2+ channels with omega-conotoxin-GVIA (300 nM), omega-agatoxin-IVA (3 microM) (a concentration well above that used to block P channels, inhibits Q type channels, but spares N type channels), inhibited the residual response to the same degree as omega-conotoxin-MVIIC alone. 4. Results suggest that neurotransmission in rat urinary bladder is supported by both N and Q type Ca2+ channels.
Frew
R
R
Defence Research Establishment Suffield, Alberta, Canada.
Lundy
P M
PM
D000818:Animals; D002118:Calcium / Q000502:physiology; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D015220:Calcium Channels / Q000145:classification / Q000502:physiology*; D004347:Drug Interactions; D004351:Drug Resistance; D004558:Electric Stimulation; D066298:In Vitro Techniques; D008297:Male; D009043:Motor Activity / Q000187:drug effects; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology; D010455:Peptides / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013111:Spider Venoms / Q000494:pharmacology; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology*; D013779:Tetrodotoxin / Q000494:pharmacology; D001743:Urinary Bladder / Q000187:drug effects / Q000294:innervation*; D020867:omega-Agatoxin IVA; D020866:omega-Conotoxin GVIA; D020960:omega-Conotoxins
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D010455:Peptides; D013111:Spider Venoms; D020867:omega-Agatoxin IVA; D020960:omega-Conotoxins; C075851:omega-conotoxin-MVIIC; D013779:Tetrodotoxin; D020866:omega-Conotoxin GVIA; D002118:Calcium