Orville A. Smith

Mechanisms of Cardiac Control in Exercise

Left ventricular performance during spontaneous exercise has been continuously analyzed in terms of direct recordings of diameter, effective pressure and other parameters derived by electronic computors. The changes in left ventricular performance during treadmill exercise have been compared with a number of experimentally induced responses in the same intact unanesthetized dog on the same day. These direct comparisons revealed that experimentally-induced increased venous return, reduced peripheral resistance, or administration of autonomic hormones do not reproduce the spontaneous exercise response. Better reproductions of the exercise response could be achieved by careful administration of isopropyl arterenol (Isuprel), by combined administration of epinephrine or norepinephrine) and experimental tachycardia or by stimulating sympathetic nerves to the heart. Stimulation of discrete areas in the diencephalon reproduced the exercise response with remarkable accuracy without movement or evidence of distress.

Nerve conduction velocity, microscopic, and electron microscopy studies comparing repaired adult and baby monkey median nerves

Three to three and a half years after repair of monkey nerves, comparison of total myelinated nerves, electron microscopic sections, and nerve conduction velocities delineated no significant difference between nerves sutured in adult life and those sutured in infancy. Extrapolating these results to the human clinical situation, central nervous system adaption in young patients could explain the better clinical results.

Changes in Peripheral Blood Flow Distribution in Healthy Dogs

The instantaneous velocity and the integrated flow through a splanchnic artery (superior mesenteric or hepatogastric), the renal artery, and the terminal abdominal aorta were recorded continuously and simultaneously, as were the mean aortic pressure and heart rate, during a wide variety of spontaneous cardiovascular adjustments of healthy active dogs. These responses were compared with the effects of infusing vasoactive substances, such as isoproterenol, l-epinephrine, norepinephrine, acetyichol lie, and Pitressiii, and with P to stimulation of selected sites in the base of the brain. During sponta neous activity, the flow through the splanch nic and renal arteries usually varied in a direction opposite to that of changes in flow to the hindciuarters. The changes in mesen teric or renal flow were relatively slight, even during strenuous exercise that produced a substantial increase in flow to the hindciuar ters. Vasoactive substances tended to produce changes in the same direction in all three beds. Changes in flow distribution and in wave forms of the instantaneous flow patterns produced by vasoactive substances did not resemble those produced by spontaneous ad justment. 1-lowever, stimulation of selected diencephalic sites (e.g., 112 fields of Forel) produced changes in both flow distribution and flow velocity patteras that closely simu lated those observed during exercise in the same animals. Stimulation in the same re gions was previously reported to produce changes in left ventricular performance also closely resembling those noted during tread mill exercise.

Cardiovascular Concomitants of the Conditioned Emotional Response inthe Monkey

Flow transducers were surgically implanted on the terminal aorta of five monkeys. A classical conditioning procedure, in which a light preceded a brief shock, was superimposed upon a variable-interval schedule of food reinforcement for key pressing (three monkeys) and alternated with an avoidanceschedule of shock reinforcement for key pressing (two monkeys). Suppression of the rate of the response of key pressing and sizable increase in blood flow and heart rate during the light were obtained for all animals.

Inhibition of the carotid sinus reflex by stimulation of the inferior olive.

A projection of nerve fibers from rostral brainstem areas, which produce pressor responses and tachycardia, terminates in the inferior olive. Electrical stimulation of the olive in the cat produces no cardiovascular response but inhibits the depressor cotnponent of the carotid sinusreflex.

Afferent projections to the hypothalamic area controlling emotional responses (HACER)

The Mesulam technique for horseradish peroxidase was used to study the subcortical afferent projections to a location in the hypothalamus that has been shown to control the complete cardiovascular (CV) response accompanying a specific emotional behavior. Major projections common to all baboons injected included the lateral septal nucleus; medial, cortical and basal amygdala; the anteroventral third ventricle area; the preoptic areas; the subiculum; the paraventricular nucleus of the thalamus; periventricular gray and the central gray of the midbrain; the midbrain tegmentum; locus ceruleus, parabrachial and raphe cells in the pons; and in the medulla, raphe nuclei, the nucleus of the solitary tract, in and around the dorsal motor nucleus of the vagus, and in the region of the nucleus ambiguus. Other projections in some but not all baboons included the subfornical organ and the midline and dorsomedial nuclei of the thalamus. The nucleus of the diagonal band of Broca was labeled to some degree with all injections but was most heavily labeled with the injection extending more laterally in the hypothalamus. These results fit well with physiological and behavioral studies dealing with neural control of emotional and CV responses and support the concept of an integrative area in the hypothalamus concerned specifically with the control of CV response accompanying emotion.

Cardiovascular responses in anticipation of changes in posture and locomotion

Measurements were made in 29 adult baboons that were housed in social groups, allowing the occurrence of the full range of species-specific behavioral interactions. The cardiovascular variables measured included blood pressure, heart rate, renal blood flow, lower limb blood flow, and occasionally mesenteric blood flow. The data were telemetered from backpacks worn by the animals and were recorded in analogue form on a polygraph, digitally on a computer and were also recorded on the audio channels of videotape being made of the behavior and social interactions of the baboons. The video and the computer recordings were synchronized by a timing system that made it possible to relate the cardiovascular responses to the behavioral responses. A numerically based behavioral code was developed that allowed the categorization of the totality of the behavior, including postural and locomotor changes. Comparisons between baseline cardiovascular values and those occurring 1 s before the initiation of a movement or posture change gave no evidence of anticipatory cardiovascular responses unless the movement was associated with behavior that included emotional content. Hypothalamic perifornical lesions reduced or eliminated these anticipatory changes.

LATERAL GENICULATE NUCLEUS AND CEREBRAL CORTEX: EVIDENCE FOR A CROSSED PATHWAY.

Lesions were placed in the lateral geniculate nucleus of cats, and degeneration was traced in the brains after survival times ranging from 5 to 21 days. Degenerated fibers could be seen in the corpus callosum and in the lateral and suprasylvian gyri of the opposite hemisphere. Results suggest the presence of a crossed geniculocortical pathway.

A system to acquire and record physiological and behavioral data remotely from nonhuman primates

An integrated system to record physiological and behavioral variables from nonhuman primates in social groups is described. The system records data simultaneously from two animals in family groups of five. It synchronizes behavioral and physiological data within 16 ms, either online or from recordings. Behavioral data are entered by trained observers online or from videotape. Recordings of physiological data are produced online as stripchart records, tape recordings on the audio channels of video cassettes, and magnetic disk files. The physiological data include two arterial blood flows, arterial blood pressure, and heart rate. The data are transmitted from freely behaving animals to a central site via radio telemetry. The infrared link controls the radio transmitter and physiological signal-processing electronics, as well as two sources of drugs for each animal. All of the electronics are contained in a small, light backpack that can be worn by either male or female baboons.<<ETX>>

Interrelation Between Central and Peripheral Mechanisms Regulating Blood Pressure

Electrical stimulation of selected discrete sites in the diencephalon induced a profound and coordinated response consisting of increased respiratory activity, limb movements, and cardiovascular adjustments. The effects on the cardiovascular system were similar to those of exercise, although the increases in aortic pressure, left ventricular pressure, and heart rate were greater. Massive splanchnicnerve discharge occurred immediately when the diencephalon was stimulated, but splanchilic activity abruptly fell below control levels with cessation of the stimulus. The increase in respiratory activity and the organized running movements seen during stimu lation apparently did miot contribute to the pressor and cardioaccelerator responses. There appeared to be no marked difference between control and diencephalic-stimulation experiments in the ease with which in duced pressure pulsations in the partially isolated carotid sinus caused bradycardia and blood-pressure depression. It may be that the influences of the diencephalon and carotid- sinus reflex upon blood pressures are inde pendent and sum algebraically. Experiments in which effects of epinephrine on splanchnic-nerve activity and systemic arterial pressure were measured before and during dieneephalic stimulation did not support the concept that catecholamines have an important role in normal pressor responses.