Effects of pharmacological autonomic blockade upon cardiac rate and blood pressure conditioned and unconditioned responses in Macaca mulatta.

Heart rate, systolic and diastolic blood pressures were recorded during classical delay conditioning of rhesus macaque monkeys. When portions of the autonomic nervous system were selectively blocked by pharmacological agents, it appeared that the initial increases in heart rate and blood pressures in response to the conditioned stimulus were the result of increased sympathetic activity and a concomitant decrease in parasympathetic activity. Towards the end of the conditioned stimulus, an increase in parasympathetic activity was indicated. Blockade of the autonomic system which produced total elimination of the conditioned cardiac rate response and substantial reduction or elimination of the conditioned blood pressure response, was not necessarily or always accompanied by a corresponding elimination of the respective unconditioned responses. Such a finding suggests a different underlying neural mediation of these conditioned and unconditioned responses.

Classical conditioning of heart rate and blood pressure in Macaca mulatta.

Classical delay conditioning of heart rate, and of systolic and diastolic blood pressures, was carried out in 16 rhesus monkeys. Blood pressure and inter-systolic interval were measured from an in-dwelling arterial catheter; recordings were taken prior to conditioned stimulus (CS) on each trial, during a 20 sec visual stimulus that filled the conditioned-unconditioned stimulus (CS-UCS) interval, and following UCS (a brief electric tail-shock). The heart rate response both to CS and to UCS was biphasic (acceleration followed by deceleration); the blood pressure response functions were more complex, and were different for the CS and post-UCS periods. Comparison of the patterns of cardiac and blood pressure responses on any trial indicates a possible sequence of baroreceptor reflex activity.