Bed nucleus of the stria terminalis alpha(1)-adrenoceptor modulates baroreflex cardiac component in unanesthetized rats.

Abstract

The bed nucleus of stria terminalis (BST) has a tonic modulating role on the baroreflex parasympathetic component. In the present study, we verified that local BST-adrenoceptors modulate baroreflex-evoked bradycardiac responses in unanesthetized rats. Bilateral microinjection of the selective alpha(1)-adrenoceptor antagonist WB4101 (15 nmol/100 nL) into the BST increased the gain of reflex bradycardia in response to mean arterial pressure increases caused by intravenous (i.v.) infusion of phenylephrine, suggesting that BST alpha(1)-adrenoceptors modulate baroreflex bradycardiac response. Bilateral microinjection of either the selective alpha(2)-adrenoceptor antagonist RX821002 (15 nmol/100 nL) or the non-selective beta-adrenoceptor antagonist propranolol (15 nmol/100 nL) into the BST had not affected baroreflex bradycardia. Animals were pretreated intravenously with the cholinergic muscarinic receptor antagonist homatropine methyl bromide (HMB, 1.5 mg/Kg) to test the hypothesis that activation of alpha(1)-adrenoceptors in the BST would modulate the baroreflex parasympathetic component. Baroreflex bradycardiac responses evoked before and after BST treatment with WB4101 were no longer different when rats were pretreated with HMB. These results suggest that parasympathetic activation accounts for the effects saw after BST pharmacological manipulation and ruling out the possibility of a sympathetic withdraw. In conclusion, our data point out that local alpha(1)-adrenoceptors mediate the BST tonic influence on the baroreflex bradycardiac response modulating parasympathetic cardiac activity.

• Authors: Carlos C Crestani, Fernando H F Alves, Leonardo B M Resstel, Fernando M A Correa
• Journal: Brain research (Brain Res) Vol. 1245 Pg. 108-15 (Dec 15 2008) ISSN: 1872-6240 [Electronic] Netherlands
• PMID: 18950605 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Adrenergic alpha-Antagonists
• Dioxanes
• Receptors, Adrenergic, alpha
• Tropanes
• homatropine methylbromide
• (2-(2',6'-dimethoxy)phenoxyethylamino)methylbenzo-1,4-dioxane

Topics

• Adrenergic alpha-Antagonists (administration & dosage, toxicity)
• Animals
• Baroreflex (drug effects, physiology)
• Blood Pressure (drug effects, physiology)
• Bradycardia (chemically induced, physiopathology)
• Dioxanes (administration & dosage, pharmacology)
• Heart Rate (drug effects, physiology)
• Male
• Microinjections
• Parasympathetic Nervous System (drug effects, physiology)
• Rats
• Rats, Wistar
• Receptors, Adrenergic, alpha (metabolism, physiology)
• Septal Nuclei (cytology, drug effects, physiology)
• Tropanes (administration & dosage, toxicity)