Leo V. DiCara

Instrumental Learning of Vasomotor Responses by Rats: Learning to Respond Differentially in the Two Ears

Curarized and artificially respirated rats were rewarded by electrical stimulation of the brain for changes in the balance of vasomotor activity between the two ears. They learned vasomotor responses in one ear that were independent of those in the other ear, in either forepaw, or in the tail, or of changes in heart rate or temperature. In addition to implications for learning theory and psychosomatic medicine, these results indicate a greater specificity of action in the sympathetic nervous system than is usually attributed to it.

Instrumental learning of systolic blood pressure responses by curarized rats: dissociation of cardiac and vascular changes.

&NA; Rats with skeletal muscles paralyzed by curare to rule out the effect of muscular activity were given artificial respiration and were rewarded by escape and/or avoidance of mild electric shock for either increasing or decreasing their systolic blood pressure. A chronic catheter was implanted within the abdominal aorta for measurement of same. Each trial was signaled by the onset of a light and tone; each experimental rat was yoked to a control rat. The yoked control received exactly the same treatment as the experimental S, except that it could do nothing to avoid being shocked, and was shocked whenever the experimental S was shocked. Over‐all group increases and decreases of 22.3% and 19.2%, respectively, were obtained for the experimental groups, and were significantly different from the changes in the control groups. All experimental Ss without exception changed their blood pressure in the rewarded direction. Analyses of heart rate and temperature did not reveal any significant changes either between experimental groups at the beginning, at the end of training, or within experimental groups during training. Implications for learning theory, psychosomatic pathology, and treatment are discussed.

Heart-rate learning in the noncurarized state, transfer to the curarized state, and subsequent retraining in the noncurarized state ☆

Abstract One group of freely-moving rats was trained to increase, and another to decrease, heart rate in order to avoid and/or escape electric shock. This training produced a statistically reliable difference between the groups. This difference persisted when the rats subsequently were tested and then given additional training while paralyzed with curare and maintained on artificial respiration. The same difference also persisted during subsequent nonreinforced tests without curare and was further increased by additional reinforced training in the normal, free-moving state. During the initial session of noncurarized training, the group rewarded for increases in heart rate showed more activity than the one rewarded for decreases, but there were no reliable differences in respiration rate. At the end of the second session of noncurarized training, the difference between the groups did not approach statistical reliability in activity (t=0.7), respiration rate (t=0.2), or the variability of that rate (t=0.6), but was highly reliable in heart-rate (t=7.2, df=12, p

Analysis of arterial blood gases in the curarized, artificially respira ted rat

The present paper describes a simple and accurate technique for the artificial respiration of curarized rats that avoids the trauma involved in a tracheotomy. Success of the technique depends on the proper positioning of a special face mask on the rat. The results of an experiment on arterial blood gases in 48 curarized rats are presented to illustrate the accuracy and effectiveness of the techniques described.

Bar pressing for food reinforcement after lesions of efferent pathways from lateral hypothalamus

Abstract Lesions were placed in the major known efferent fiber pathways of the lateral hypothalamic feeding area of rats in an attempt to determine the route by which signals relevant to food-motivated behavior are conveyed to extrahypothalamic structures. The rats with lesions were deprived of food for 24 hr and then placed in a Skinner box where bar presses delivered food pellets. While lesions within the lateral hypothalamic feeding area resulted in gross decrements in bar pressing, large lesions of the medial forebrain bundle rostral or caudal to the lateral hypothalamic feeding area or of the periventricular fiber system produced no decrements in comparison to control rats.

Learning of blood pressure responses in the noncurarized rat: Transfer to the curarized state

Abstract Nine free-moving rats were trained to increase, and eight to decrease, systolic blood pressure in order to avoid and/or escape electric shock. The initial difference in blood pressure between the two groups was small and did not approach significance. The training produced changes in the rewarded directions, with the difference between the changes being reliable and producing an overall difference of 9.7 mm Hg. No corresponding changes were found for heart rate or gross skeletal acfivity. The blood pressure responses failed to transfer to the curarized state. However, subsequent training in the curarized state produced a difference between the increase and decrease groups of 21.2 mm Hg. There was some indication that the blood pressure responses in the curarized and noncurarized training sessions were positively correlated.

Neonatal sympathectomy by 6-hydroxydopamine: Cardiovascular responses in the paralyzed rat ☆

Abstract Rats who had been neonatally sympathectomized by peripheral injections of 6-hydroxydopamine or vehicle were paralyzed by succinylcholine and received either atropine or saline injection. Heart rate and blood pressure responses to foot shocks and to a conditioned stimulus (CS) for shock were continuously recorded. Sympathectomized rats showed lower basal systolic blood pressure, less second to second blood pressure variability and attenuated pressor responses to the shock and the CS. Basal heart rate and the heart rate response to shock were were unaffected by sympathectomy, but cardiac rate deceleration to the CS was ablished. Atropine increased basal heart rate, decreased heart rate variability and abolished the cardiac deceleration to the CS. These data were interpreted as suggesting that conditioned cardiac deceleration in the rat is a vagal mediated response compensatory to prior blood pressure increases. Sympathectomized rats also showed higher core temperatures under paralysis.