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Omega-conotoxin GVIA, the N-type calcium channel inhibitor, is sympatholytic but not vagolytic: consequences for hemodynamics and autonomic reflexes in conscious rabbits.
- Source :
-
Journal of cardiovascular pharmacology [J Cardiovasc Pharmacol] 1990 Oct; Vol. 16 (4), pp. 675-80. - Publication Year :
- 1990
-
Abstract
- We investigated the effects of the N-type calcium channel blocking agent, omega-conotoxin GVIA, on the resting hemodynamics and on some autonomic reflexes in the conscious rabbit. omega-Conotoxin 3 and 10 micrograms/kg i.v. reduced mean arterial blood pressure by 16 +/- 2 and 25 +/- 3 mm Hg, respectively, over 30 min accompanied by a tachycardia. Renal vascular conductance (Doppler flowmeter) increased by 27.6 +/- 3.7 and 38.6 +/- 10.3% at 30 min after omega-conotoxin 3 and 10 micrograms/kg, respectively. Vasodilatation was also observed but to a lesser extent in the hindquarter and mesenteric vascular beds. The baroreceptor-heart rate reflex was evoked by a drug method (bolus injection of sodium nitroprusside and phenylephrine) and by inflation of perivascular balloons implanted on the thoracic vena cava and aorta. omega-Conotoxin (3 micrograms/kg) abolished the sympathetic component of the cardiac baroreceptor reflex without affecting vagal efferent activity. In addition, marked vagal-mediated bradycardia from (a) the "Bezold-Jarisch-like" reflex evoked by serotonin (1-10 micrograms/kg i.v.) and (b) the nasopharyngeal reflex evoked by cigarette smoke were unaffected by omega-conotoxin (3-10 micrograms/kg). We conclude that omega-conotoxin-induced N-type calcium channel blockade abolishes sympathetic but not vagal cardiac efferent activity. The hypotension and peripheral vasodilatation are probably due to the prejunctional sympatholytic action of the peptide. These N-type calcium channels are thus limited to the sympathetic varicosities in the rabbit.
- Subjects :
- Analysis of Variance
Animals
Drug Evaluation, Preclinical
Heart Rate drug effects
Male
Nasal Cavity innervation
Neurons, Efferent drug effects
Pressoreceptors drug effects
Rabbits
Reflex drug effects
Splanchnic Circulation drug effects
omega-Conotoxin GVIA
Calcium Channel Blockers pharmacology
Hemodynamics drug effects
Peptides, Cyclic pharmacology
Sympatholytics pharmacology
Vagus Nerve drug effects
Subjects
Details
- Language :
- English
- ISSN :
- 0160-2446
- Volume :
- 16
- Issue :
- 4
- Database :
- MEDLINE
- Journal :
- Journal of cardiovascular pharmacology
- Publication Type :
- Academic Journal
- Accession number :
- 1706812
- Full Text :
- https://doi.org/10.1097/00005344-199010000-00022