The role of N-type Ca2+ channels in regulating excitability of guinea-pig sympathetic neurones.
Ca2+ entry through voltage-gated channels activated during the action potential modifies neuronal excitability by activating several types of K+ channel. We have determined the effects of Ca2+ influx through N-type Ca2+ channels in sympathetic paravertebral neurones of the guinea-pig, using the specific antagonist, omega-conotoxin GVIA. Blockade of large conductance (BK) Ca2(+)-activated K+ channels slowed action potential repolarization but did not affect the peak amplitude of the conductance (gKCal) underlying the afterhyperpolarization. Blockade of small conductance (SK) Ca2(+)-activated K+ channels decreased gKCal but did not affect action potential repolarization. Blockade of N-type Ca2+ channels slowed action potential repolarization and reduced the peak amplitude of gKCa1. We conclude that Ca2+ entry via N-type channels activates both BK and SK channels in guinea-pig sympathetic neurones. This differs from our previous observations in rat sympathetic neurones.
Ireland
D R
DR
Prince of Wales Medical Research Institute, Randwick, NSW, Australia. d.ireland@unsw.edu.au
Davies
P J
PJ
McLachlan
E M
EM
D000818:Animals; D001030:Apamin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000502:physiology*; D003035:Cobalt / Q000494:pharmacology; D005260:Female; D006168:Guinea Pigs; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology; D051036:Large-Conductance Calcium-Activated Potassium Channels; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009474:Neurons / Q000737:chemistry* / Q000187:drug effects / Q000502:physiology*; D018408:Patch-Clamp Techniques; D010455:Peptides / Q000494:pharmacology; D015221:Potassium Channels / Q000502:physiology; D024681:Potassium Channels, Calcium-Activated; D051640:Small-Conductance Calcium-Activated Potassium Channels; D017783:Superior Cervical Ganglion / Q000737:chemistry* / Q000166:cytology / Q000502:physiology; D020866:omega-Conotoxin GVIA
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D051036:Large-Conductance Calcium-Activated Potassium Channels; D010455:Peptides; D015221:Potassium Channels; D024681:Potassium Channels, Calcium-Activated; D051640:Small-Conductance Calcium-Activated Potassium Channels; D001030:Apamin; D003035:Cobalt; C064719:iberiotoxin; D020866:omega-Conotoxin GVIA; D002118:Calcium