Effects of pentobarbital sodium anesthesia and neurohumoral agents on the cardiac orienting reflex

Studies of the cardiac orienting reflex in 16 dogs, moderately anesthetized and awake are reported. In the anesthetized dogs prominent transient heart rate decrease was commonly noted within one or two beats after the onset of various auditory stimuli, and less often after visual stimuli. This cardiac inhibition was neither as prominent nor as frequent in occurrence in awake dogs. The respiratory cycle at stimulus onset influenced the appearance and degree of heart rate decrease, with the greatest and most frequent decreases occurring during the expiratory phase. Atropine abolished the response. There was little evidence of habituation of this orienting response under anesthesia, although “waxing” and “waning” apparently related to minute-by-minute fluctuations in degree of unconsciousness, occurred. These findings are discussed in relation to neurophysiological and neuroanatomical correlates of orienting responses, hypotheses of orienting and attention and cardiovascular neurohumoral mediators.     

The role of inhibition in neurotic behavior

Neurotic behavior is explained according to the theory of Pavlov as collision between excitation and inhibition. This internal inhibition imposes a burden on the nervous system. The stress can be relieved by what Pavlov called external inhibition, which is actually excitation of another activity. This principle is applied to the human being in explaining the interaction between nervous centers, the advantage of voluntary self-discipline over imposed discipline. Rioting and social unrest is explained in the terms of conflict between excitation and inhibition.     

Effect of movement on the cardiac conditional reflex

The cardiac component of the motor conditional reflex to a faradic stimulus to the hind leg in three dogs was measured. The leg was paralyzed by crushing 4 to 5 anterior roots of the lumbar nerves (second to sixth). The cardiac experiments were repeated beginning four days after operation and measurements were taken of the cardiac conditional reflex. A comparison of the increase in cardiac rate to the conditional stimulus before and after operating showed no significant difference in spite of the fact that the dog was unable to lift his leg to the stimulus. From this we conclude that the execution of the movement is not necessary for the increase of heart rate in the cardiac conditional reflex.