Behaviorally conditioned changes in atrio-ventricular transmission in awake dog

Changes in autonomic control of heart associated with classical appetitive conditioning in rats

The aim of this study was to examine the changes in autonomic control of the heart associated with classical appetitive conditioning in rats. We trained rats to learn that a movement into a test chamber was followed by delivery of reward (contextual conditioning) and performed power spectral analysis of heart rate variability from electrocardiograms recorded using the telemetry system. We investigated the sympathovagal balance of autonomic regulation of the heart in response to not only the conditioned stimulus (the movement into the test chamber), but also the unconditioned stimulus (reward), and compared the results of these two kinds of emotional states; it might be considered that "the reward-expecting state" is evoked by the conditioned stimulus and "the reward-receiving state" is evoked by the unconditioned stimulus in rats. The reward-expecting state resulted in a significant increase in both low frequency (LF) power and high frequency (HF) power with no change in heart rate (HR) and LF/HF ratio, indicating that both sympathetic and parasympathetic activity increased with no change in sympathovagal balance. The reward-receiving state resulted in a significant increase in HR and a significant decrease in LF power, HF power, and LF/HF ratio, indicating that both sympathetic and parasympathetic activity decreased with predominance in the parasympathetic activity. These results suggest that the method performed in our present study might be useful for distinguishing between two different emotional states evoked by classical appetitive conditioning in rats.

Separate controls for conditioned cephalic phases of acid secretion and drinking in the rat

Adult male Sprague-Dawley rats, surgically equipped with a stainless steel gastric cannula, were tested in a paradigm known to support conditioning of cephalic phase gastric acid secretion. Rats were tested first under (a) baseline conditions--prepared to sham feed, but no food was offered and none should have been expected; then (b) 5 conditioning trials--prepared and allowed to sham feed sweetened milk; and finally (c) extinction trials--prepared to sham feed milk, but milk was not offered. Combined antagonism of H1 and H2 histamine receptors (using intraperitoneal dexbrompheniramine plus cimetidine) prevented the acquisition of conditioned cephalic phase of acid secretion, but had no effect on acquisition of conditioned water intake. Such histaminergic antagonism also blocked the expression of an established conditioned acid secretory response without effect on conditioned water intake; peripheral cholinergic blockade using atropine methyl nitrate had virtually the same effect as did histaminergic antagonism. The converse was observed following blockade of angiotensin II synthesis using subcutaneous captopril: Established conditioned secretion was unaffected, but conditioned water intake was inhibited. These results dissociate the physiological controls for conditioned responses which occur simultaneously in rats anticipating eating: Peripheral histamine mediates the acquisition and expression of the conditioned cephalic phase of acid secretion, whereas angiotensin II appears to mediate at least the expression of conditioned water intake.

Autonomic correlates of alimentary conditioned and unconditioned reactions in the dog

Analysis of changes in cardiac action and the secretion of saliva during unconditioned alimentary activity in 6 dogs revealed that the beginning of food consumption was accompanied by acceleration of the heart rate (HR) without an increase in salivation. In the course of eating, the heart rate decelerated and salivation increased. Alimentary conditioned stimuli of excitatory (CS+) and inhibitory (CS-) character always produced cardiac acceleration, which in the case of CS+ was accompanied by secretion of saliva. The findings indicate that during food consumption activation of the autonomic system depends upon the contents of motivational processes. In the course of an alimentary act the parasympathetic withdrawal (heart rate acceleration and decrease in salivation) seems to reflect the drive component of the act, while the following parasympathetic activation (heart rate deceleration and increase in salivation) is probably associated with an hedonic component of the consummatory reaction. In our study alimentary conditioned stimuli evoked both drive and hedonic components of alimentary motivation.