Pharmacological dissection of high-voltage-activated Ca2+ current types in acutely dissociated rat supraoptic magnocellular neurons.
1. We used pharmacological blockers and whole cell voltage-clamp recordings from acutely dissociated magnocellular neurons from the rat supraoptic nucleus to test for the presence of L-, N-, P-, Q-, and R-type calcium currents. 2. We found clear evidence for L-type (dihydropyridine sensitive), N-type (blocked by omega-conotoxin (GVIA), and P-type (blocked by omega-agatoxin IVA) currents. Nifedipine blocked 28 +/- 2% (mean +/- SE) of the current, omega-conotoxin GVIA blocked 26 +/- 4%, and omega-agatoxin IVA (25-30 nM) blocked 17 +/- 4%. In addition, omega-conotoxin MVIIC blocked about half (54 +/- 2%) of the current remaining after L-, N-, and P-type currents were blocked, suggesting the presence of Q-type currents. 3. About 20% of the whole cell current was unblocked by the combination of all four blockers, suggesting the presence of a fifth current type. This residual current inactivated slowly at -10 mV.
Foehring
R C
RC
Department of Anatomy and Neurobiology, University of Tennessee, Memphis 38163, USA.
Armstrong
W E
WE
D000818:Animals; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000187:drug effects / Q000378:metabolism*; D020864:Calcium Channels, N-Type; D007032:Hypothalamus, Anterior / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D066298:In Vitro Techniques; D015640:Ion Channel Gating; D008297:Male; D009474:Neurons / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D051381:Rats; D017207:Rats, Sprague-Dawley
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D020864:Calcium Channels, N-Type