Autonomic control of heart rate and blood pressure in spontaneously hypertensive rats during aversive classical conditioning.

Examined heart rate (HR) and blood pressure (BP) responses of 26 spontaneously hypertensive rats (SHR) and 21 genetically-controlled Wistar/Kyoto (WKY) rats during aversive classical conditioning. Assessments were made of the effects of selective autonomic blockade by methyl atropine (10 mg/kg), phentolamine (2 mg/kg), and propranolol (2 mg/kg). The decelerative SHR HR CR was not secondary to baroreceptor reflex activity, although such activity was involved in the pressor BP and decelerative HR orienting response (OR) and UCR complex of the SHRs on initial applications of the CS and UCS. Augmented pressor BP ORs, CRs, and UCRs in the SHRs and differential drug effects on BP and HR baselines of the 2 strains suggested the presence of enhanced sympathetic activity in the SHRs that was not reflected in the SHR decelerative HR CR. Phentolamine unmasked evidence of reflex beta?-vasodilation deficiency in the SHRs that could have contributed to the enhancement of their BP OR and CR. (27 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)