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The role of arginine vasopressin on peripheral cardiac parasympathetic nerve function in the rat.

Abstract：

:In rats, arginine vasopressin augments bradycardia associated with baroreflex activation. We investigated whether modulation of peripheral cardiac parasympathetic nerve function by AVP may play a role in this effect. To accomplish this we utilized an in vivo model with which we previously demonstrated both adrenergic and peptidergic modulation of cardiac parasympathetic nerve function. Urethane-anesthetized rats (250-350 g) were prepared with arterial and venous catheters and ECG leads. The cervical vagi were sectioned, and propranolol (1 mg/kg, i.v.) was administered to eliminate reflex changes in heart rate. To investigate potential preganglionic modulation by AVP, the right vagus nerve was electrically stimulated (0.5 mA; 0.5 msec; 1-10 Hz). To observe postganglionic effects through nicotinic activation, carbachol (a mixed nicotinic and muscarinic agonist) was injected (0.5 to 4.0 micrograms/kg, i.v.). To observe direct cholinergic effects at the SA node, methacholine (a pure muscarinic agonist) was injected (0.5 to 4.0 micrograms/kg). All three trials were performed before (control) and during AVP infusion (20 micrograms.kg.min). No consistent, significant differences in vagal-, carbachol- or methacholine-induced bradycardia were observed between control and AVP groups. Since endogenous plasma levels of AVP in the control situation may have saturated any vasopressinergic effect prior to AVP infusion, the experiments were repeated in Brattleboro rats, genetically deficient in AVP. Again, no consistent differences in heart rate responses to parasympathetic activation were noted between control and AVP-infused groups. These results suggest that in rats, vasopressinergic augmentation of baroreflex-induced bradycardia is not mediated by an effect on the peripheral cardiac parasympathetic innervation. However, it remains to be investigated whether AVP-mediated sympathetic withdrawal disinhibits cardiac parasympathetic nerve function.

journal_name

Ann N Y Acad Sci

journal_title

Annals of the New York Academy of Sciences

authors

Pardini BJ,Lund DD,Schmid PG

doi

10.1111/j.1749-6632.1993.tb55560.x

subject

Has Abstract

pub_date

1993-07-22 00:00:00

pages

363-74

eissn

0077-8923

issn

1749-6632

journal_volume

689

pub_type

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The role of arginine vasopressin on peripheral cardiac parasympathetic nerve function in the rat.