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- Title
Involvement of Different Calcium Channels in the Depolarization-Evoked Release of Noradrenaline from Sympathetic Neurones in Rabbit Carotid Artery.
- Authors
Uhrenholt, Torben R.; Nedergaard, Ove A.
- Abstract
The calcium channels coupled to noradrenaline release from sympathetic neurones in the rabbit isolated carotid artery were examined. Rings of carotid artery were preloaded with (-)-[3H]noradrenaline and the fractional 3H overflow evoked by electrical-field stimulation was determined by liquid scintillation spectrometry. The N-type Ca2+ channel blocking agent ω-conotoxin GVIA (3×10−9-6×10−8 M) reduced the stimulation-evoked 3H overflow. The maximal inhibition was seen with 3×10−8 M. The maximal reduction was more marked at a low (2 Hz) stimulation frequency than at a high one (30 Hz). Mibefradil (10−6 M) irreversibly reduced the 3H overflow evoked by field stimulation (2 Hz). At 30 Hz, the reduction was more marked than at 2 Hz. Mibefradil (3×10−6–10−5 M) enhanced the passive 3H outflow. The reduction of the stimulation (30 Hz)-evoked 3H overflow seen with ω-conotoxin GVIA (3×10−8 M) was enhanced by mibefradil (10−6 M) and unaffected by nimodipine (10−5 M) and ω-agatoxin IVA (10−8 M). We conclude that the stimulation-evoked release of noradrenaline from sympathetic neurones in rabbit carotid artery at a low frequency (2 Hz) is mediated mainly by the N-type calcium channels. At a high frequency (30 Hz), T-type Ca2+ channels are also involved.
- Subjects
CALCIUM channels; NORADRENALINE; NEURONS; CAROTID artery; SCINTILLATION spectrometry; ION channels
- Publication
Basic & Clinical Pharmacology & Toxicology, 2005, Vol 97, Issue 2, p109
- ISSN
1742-7835
- Publication type
Article
- DOI
10.1111/j.1742-7843.2005.pto_90.x