Osmolarity of the blood and paradoxical sleep

Two observations led us to investigate the relationship between the periodicity of P.S. and changes in the osmolarity of the blood. Firstly it appears that copious forcing of fluids (120-160 ml) causes P.S. to disappear for several hours; we therefore administered 60 ml twice daily. Secondly, we had observed that certain states of dehydration (in the transitory diabetes insipidus following transection of the brain stem leaving a hypothalamic island) are accompanied by a marked, transitory increase in P.S., up to 20-30% of the total time. Fig. 23 shows the results of our investigations on the relationship between the osmolarity of the blood and P.S. in pontile cats with hypothalamic island.

(i) Hypo-osmolarity of the b]ood was obtained by drip infusion of a quantity of tepid water equalling 10% of the body weight, via a stomach tube over 30-60 min, together with injection of 1-2 units of an antidiuretic hormone. This treatment completely suppressed P. S. for 6- 10 h. P. S. then returned in short (1-2 min), infrequent episodes. It was found that dilatation of the stomach by the same quantity of air did not affect the rhythm or duration of P.S.

(ii) Hyper-osmolarity was obtained either by comp]ete withdrawal of liquid for 24 h and forcing an equivalent quantity of dehydrated food, or by intravenous injection of 20 ml of 20% hypertonic saline. In the latter instance the duration and frequency of P.S. increased a]most immediate]y and remained high for 5-6 h. When liquids were withheld the increase in P.S. was maintained for 24 h, but as the state of the animal deteriorated with continued dehydration (polypnea) the phases of P.S. diminished in duration and frequency and final]y disappeared. Resumption of normal hydration after 24 h was accompanied by an immediate return to norma] of the P.S. rhythm. A curious phenomenon was observed in all cases during the first phases of P.S. following resumption of a liquid diet: the appearance of a very regular rhythmic activity of 3-4 c/s in the pontine reticular formation (Fig. 24), first in bursts of several seconds associated with the pontine spikes, and then continuously until the reappearance of EMG activity. Such a pattern has never been observed in the waking state.