Effect of acute inhibition of nitric oxide synthesis by L-NAME on cardiovascular responses following peripheral autonomic blockade in rabbits.

Abstract

The pressor and chronotropic responses to acute inhibition of nitric oxide synthase enzyme by N(G)-nitro-L-arginine methyl ester (L-NAME) were studied in anaesthetized rabbits with intact autonomic nervous system (ANS) activity. Also, they were investigated when administration of L-NAME was preceded by peripheral autonomic blockade. Autonomic blockade had different forms: ganglionic (hexamethonium-induced), post-ganglionic beta-adrenergic blockade (propranolol induced), parasympathetic blockade (atropine induced), and complete autonomic blockade by coadministration of hexamethonium and atropine simultaneously. L-NAME injected intravenously (10 mg/kg) in animals with intact and blocked autonomic activity induced a pressor response. This pressor response was accompanied by bradycardia in rabbits with either intact autonomic activity or hexamethonium-induced ganglionic blockade. L-NAME exerted no effect on heart rate in animals with beta-adrenergic blockade or parasympathetic blockade. In rabbits with complete autonomic blockade, L-NAME evoked tachycardia. These experiments indicate that L-NAME-induced hypertension is not relying only on ANS. Also, L-NAME-induced tachycardia in rabbits treated with atropine plus hexamethonium suggests other humoral mechanisms that may be involved in the L-NAME induced chronotropic response.

• Authors: Ehab S Eldesoky
• Journal: Fundamental & clinical pharmacology (Fundam Clin Pharmacol) Vol. 20 Issue 3 Pg. 239-45 (Jun 2006) ISSN: 0767-3981 [Print] England
• PMID: 16671958 (Publication Type: Comparative Study, Journal Article)

Chemical References

• Enzyme Inhibitors
• Parasympatholytics
• Hexamethonium
• Atropine
• Propranolol
• Nitric Oxide Synthase
• NG-Nitroarginine Methyl Ester

Topics

• Animals
• Atropine (pharmacology)
• Blood Pressure
• Enzyme Inhibitors (administration & dosage, pharmacology)
• Heart (drug effects, innervation)
• Heart Rate
• Hexamethonium
• Injections, Intravenous
• Male
• NG-Nitroarginine Methyl Ester (administration & dosage, pharmacology)
• Nitric Oxide Synthase (antagonists & inhibitors)
• Parasympathetic Nervous System (drug effects)
• Parasympatholytics (pharmacology)
• Propranolol
• Rabbits
• Sympathectomy, Chemical
• Time Factors