Lesions of the amygdaloid central nucleus block conditioned cardiac arrhythmias in the rabbit receiving digitalis.
We have previously reported [15] that malignant cardiac arrhythmias can be evoked in the rabbit receiving digitalis by cardiovascular changes in response to (a) a Pavlovian aversively conditioned stimulus (CS) or (b) electrical stimulation of the amygdaloid central nucleus (ACE), a structure which contributes to Pavlovian-conditioned cardiovascular responses in the rabbit. The present study was designed to examine further the role of the ACE in arrhythmogenesis by determining the effect of lesions of the ACE on the occurrence of CS-evoked arrhythmias during digitalis administration in the rabbit. Two groups of rabbits (ACE lesion and SHAM) received electrodes implanted bilaterally in the ACE, while a third group (UNOP) served as an unoperated control. All rabbits were given Pavlovian conditioning trials in which a tone conditioned stimulus (CS) was paired with an eyelid shock as an unconditioned stimulus (US). Twenty-four h later, rabbits in the lesion group received bilateral lesions of the ACE. Twenty-four h after the lesion, rabbits in all three groups were given a retention test in which an i.v. infusion of ouabain was delivered, followed by 20 CS alone trials. Presence or absence of arrhythmias was scored during the pre-CS baseline and CS periods for each trial. All three groups exhibited few instances of pre-CS baseline arrhythmias, the frequency of which did not differ between groups. The SHAM and UNOP control groups exhibited a significant increase in the occurrence of CS-arrhythmias compared to pre-CS levels. This increase was blocked in the group receiving lesions of the ACE, as was CS-induced bradycardia which typically occurs in response to the CS in the rabbit.(ABSTRACT TRUNCATED AT 250 WORDS)
Markgraf
C G
CG
University of Vermont, Department of Psychology, Burlington.
Kapp
B S
BS
D000679:Amygdala / Q000502:physiology*; D000818:Animals; D001145:Arrhythmias, Cardiac / Q000503:physiopathology* / Q000517:prevention & control; D001919:Bradycardia / Q000503:physiopathology / Q000517:prevention & control; D003213:Conditioning, Psychological; D004071:Digitalis Glycosides / Q000494:pharmacology*; D011817:Rabbits
D004071:Digitalis Glycosides