James N. Hayward

The influence of the nasal mucosa and the carotid rete upon hypothalamic temperature in sheep

1. In chronically‐prepared sheep, intracranial temperatures were measured in the cavernous sinus among the vessels of the carotid rete and at the circle of Willis extravascularly, and in the preoptic area and in other brain stem regions. Extracranial temperatures were measured intravascularly in the carotid or internal maxillary arteries and on the nasal mucosa and the skin of the ear.

Spontaneous activity of single neurones in the hypothalamus of rabbits during sleep and waking.

1. A method is described for recording from single cells in the hypothalamus of unanaesthetized freely moving rabbits. Behaviour, bodily movement, skin and brain temperatures and e.e.g. were monitored.

Osmosensitive single neurones in the hypothalamus of unanaesthetized monkeys.

1. We recorded with tungsten micro‐electrodes the activity of single neurones in the supraoptic nucleus (NSO) and adjacent regions of the hypothalamus while repeatedly injecting solutions of varying tonicity into the common carotid artery of trained, unanaesthetized monkeys who accepted the experimental restraints without anxiety.

Autonomic Basis for the Rise in Brain Temperature during Paradoxical Sleep

The rise in brain temperature in the rabbit during paradoxical sleep originates in a temperature rise of the cerebral arterial blood. Heat loss from the ear is a major factor in the regulation of arterial blood temperature in the rabbit, and the primary thermal event in paradoxical sleep is a vasoconstriction of the skin of the ear which results in a rise in arterial blood and brain temperatures. These thermal correlates of paradoxical sleep are not present in a cold environment when the ear skin is already maximally vasoconstricted. The persistence of peripheral vasoconstriction during paradoxical sleep in a hot environment suggests a disturbance in autonomic thermoregulatory control.

Physiological and morphological identification of hypothalamic magnocellular neuroendocrine cells in goldfish preoptic nucleus

1. Intracellular recordings were made from antidromically identified neurones in the goldfish preoptic nucleus and Procion Yellow was ejected from the recording pipette, marking these magnocellular neuroendocrine cells diffusely, for histological identification.

Activity of magnocellular neuroendocrine cells in the hypothalamus of unanaesthetized monkeys. I. Functional cell types and their anatomical distribution in the supraoptic nucleus and the internuclear zone.

1. We recorded with tungsten micro‐electrodes the spontaneous and evoked activity of single cells in the supraoptic nucleus (n.s.o.) and internuclear zone (i.n.z.) of trained, unanaesthetized monkeys who accepted experimental restraints and pituitary gland stimulation without anxiety.

Activity of magnocellular neuroendocrine cells in the hypothalamus of unanaesthetized monkeys

1. We studied magnocellular neuroendocrine cells and non‐neuroendocrine cells in the supraoptic nucleus (n.s.o.) and internuclear zone (i.n.z.) in the hypothalamus of unanaesthetized, chronically prepared monkeys. After antidromic identification, functional cell typing and sensory testing we injected solutions of varying tonicity into an implanted carotid cannula to determine osmosensitivity.

Temperature Gradients Between Arterial Blood and Brain in the Monkey.

Summary Temperature measurements were made simultaneously in the arterial blood and various brain structures in 5 chronically prepared rhesus monkeys at rest in a lighted, sound-attenuated, thermoregulated chamber. The level of alertness of the animals was also noted by observing changes in overt behavior together with EEG and EMG recordings. Spontaneous and induced shifts in the level of arousal were followed in seconds by warming or cooling of the arterial blood and seconds to minutes later by parallel shifts in the temperature of the majority of the brain sites. Arterial blood temperature was thus found to yield a sensitive index of the behavioral state of the monkey in relation to sleep and arousal. Changes in the mean temperature of the arterial blood going to the brain appeared primarily responsible for temperature fluctuations in the brain. A number of steadily maintained but differing thermal gradients were found to exist between regional brain sites and the arterial blood.

Temporal patterns of vasopressin release following electrical stimulation of the amygdala and the neuroendocrine pathway in the monkey.

To evaluate a possible role of the amygdala (Amyg) in the neural control of arginine vasopressin (AVP) release, adult female monkeys (Macaca mulatta) with electrodes chronically implanted in the Amyg, hypothalamus and pituitary gland were given 5% dextrose and water infusions and were stimulated electrically at these sites. Immediately before and after, and at 5, 10, 15 and 30 min intervals following electrical stimulation, blood samples were withdrawn from unanesthetized monkeys, through implanted cardiac cannulae, for radioimmunoassay (RIA) of plasma AVP and for plasma osmolality determination. In the Amyg-stimulated monkeys, plasma AVP rose rapidly to peak values at the end of stimulation followed by an abrupt post-stimulation fall to control levels in 30 min. A small yet significant rise in plasma osmolality was also observed. Electrical stimulation of the hypothalamus and the pituitary gland yielded a temporal pattern of plasma AVP rise and fall identical to that seen following Amyg stimulation. Blood sampling, precisely timed to the onset and end of the stimulus train, was important in capturing the rise and fall in plasma AVP. Stimulus intensity determined the magnitude of plasma AVP elevation at each of these sites, with the highest current densities yielding the highest levels of plasma AVP. It is suggested that the Amyg may be involved in the neural triggering of AVP release from the neurohypophysis.

Intracranial heat exchange and regulation of brain temperature in sheep.

Abstract In the sheep, there is a dissociation between brain and body core temperature because of a temperature gradient between arterial blood of the body core and cerebral arterial blood. Cerebral arterial blood is cooler than blood in the common carotid artery by as much as 1C in the relaxed animal. During periods of arousal and of paradoxical sleep, cerebral arterial blood temperature rises toward central arterial blood temperature. The brain is warmer than the cerebral arterial blood, and changes in cerebral arterial temperature are reflected by changes in brain temperature. Vasoconstriction of the skin of the head and of the nasal mucosa is associated with elevations in temperature of the cerebral arterial blood and the brain. We have concluded that heat exchabge between the central arterial blood in the carotid rete and the cranial venous blood in the cavernous sinus is the major factory regulating cerebral arterial blood and brain temperatures in the sheep.