Figure 3 : Effect of secondary injection of 5-hydroxytryptophan during insomnia produced by p-chlorophenylalanine in the cat

(Top two lines) Normal pattern of sleep in a cat for which electroencephalographic recordings were made over a long period. (Bottom five lines) Total insomnia 96 hours after the last of three daily injections of p-chloro phenylalanine (400 milligrams per kilogram), then, following the injection (see arrow) of 5-hydroxytryptophan (5 milligrams per kilogram), reappearance of the normal pat tern of sleep. Insomnia returns 8 hours after the injection. (Base line of each record) Waking; (white rectangles) slow-wave sleep: (black rectangles) paradoxical sleep.

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