The influence of ambient temperature on sleep characteristics in the aged cat

Adrenergic and cholinergic inputs in preoptic area of rats interact for sleep-wake thermoregulation

Isolated studies have shown that both norepinephrine and acetylcholine into the medial preoptico-anterior hypothalamic area tonically regulate sleep-wake and body temperature. A possible interaction between these neurotransmitters for the regulation of such functions has been investigated in this study. To study this interaction a combination of either prazosin and carbachol or, scopolamine and methoxamine was injected into the medial preoptico-anterior hypothalamic area and the effect on sleep, wake, and rectal temperature recorded simultaneously. The combination of chemicals were selected based on our previous studies where it was observed that each of the chemicals in a combination had opposite effects. It was observed that injection of the combination expressed a resultant summated effects of individual component chemicals when injected in isolation (observed in previous studies). Because effect of neither of the chemicals in the combination was dominant, the results suggest an interaction and integration of the adrenergic and cholinergic inputs in the medial preoptico-anterior hypothalamic area for the regulation of sleep-wakefulness and body temperature.

Role of cholinergic inputs to the medial preoptic area in regulation of sleep-wakefulness and body temperature in freely moving rats

The medial preoptico-anterior hypothalamic area receives adrenergic as well as cholinergic inputs. Independent studies showed that both these inputs influence sleep, wakefulness and body temperature. The role of the adrenergic inputs was studied earlier. The role of cholinergic inputs is reported here. The cholinergic agonist, carbachol, and antagonist, scopolamine, were injected into this area during the day and the night in freely moving rats and the effects on sleep-wakefulness and body temperature studied. It was observed that carbachol induced wakefulness accompanied by a fall in body temperature while scopolamine induced an opposite effect, i.e. sleep accompanied by an increase in body temperature. This suggested that the cholinergic input into the medial preoptic area is spontaneously active in regulating sleep-wakefulness and body temperature and this regulation is mediated through muscarinic receptors present in this area. The results also suggest that, contrary to the action of adrenergic inputs (which have a dissociated effect on sleep-wakefulness and body temperature), the cholinergic input is unlikely to have a dissociated effect on those functions.

Effect of ambient temperature on sleep-waking cycle in cats with electrolytic dorsolateral pontine tegmental lesions

The effects of ambient temperature on the sleep-waking cycle were studied in intact cats and those with bilateral electrolytic lesions in the pontine tegmentum. At a room temperature of 23 degrees C, the percentage of time spent in paradoxical sleep was significantly lower in the lesioned cats than in intact animals. The mean duration of paradoxical sleep episodes was also decreased in the lesioned animals. The reduction in slow-wave sleep was not significant. At a slightly warmer ambient temperature of 30 degrees C, both the mean duration of paradoxical sleep episodes and the total duration of paradoxical sleep in the lesioned animals were increased toward normal values. Slow-wave sleep increased slightly but not significantly. At a higher ambient temperature of 35 degrees C, as well as at colder ambient temperatures of 15 and 7 degrees C, the durations of both paradoxical sleep and slow-wave sleep were significantly reduced. Under these thermal loads, the reduction in the duration of sleep was significantly greater in the lesioned cats than in the intact animals. The results suggest that: (i) pontine lesions alter the sleep cycle of cats and ambient temperature influences this alteration; (ii) the effects of thermal loads on the sleep cycle are more severe in the lesioned cats; and (iii) a moderately warm ambient temperature (30 degrees C) improves the sleep of pontine-lesioned cats.