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Regulation of blood pressure by the central nucleus of the amygdala in dynamically changing appetitive and aversive classical conditioning tasks in rats


 In an environment of dynamically changing conditions, humans and animals can determine whether a current situation is favorable to them and accordingly select actions. Autonomic cardiovascular tuning is as important as motor control for this function. However, neuronal mechanisms underlying the dynamic adjustments of autonomic cardiovascular responses remain unclear. In this study, we hypothesized that the amygdala plays a role in autonomic cardiovascular tuning in a dynamically changing situation. We recorded the blood pressures and heart rates of head-restrained rats during appetitive and aversive classical conditioning tasks. Rats learned varying associations between conditioned stimuli and unconditioned stimuli in appetitive, neutral, and aversive blocks. Blood pressure and heart rate in the appetitive block gradually increased in response to reward-predicting cue, preceded by a vigorously increased response to the actual reward. The predictive response was significantly higher than the responses in the neutral and aversive condition blocks. Blood pressure and heart rate responses to the air puff-predicting cue in the aversive block were significantly lower than that of the responses in the neutral block. The conditioned blood pressure response rapidly changed through condition switching. Furthermore, bilateral pharmacological inactivation of the central nucleus of the amygdala has significantly decreased reward-predictive pressor responses in the latter phase, but not in the initial phase of block change. These results suggest that blood pressure is adaptively tuned by positive and negative conditioned stimuli and that the central nucleus of the amygdala likely assists in maintaining pressor response in dynamically changing situations.