The Behavioural State During Climax (Hatching) in the Domestic Fowl (Gallus Domesticus)

Abstract

AbstractIn the last decade it has been proposed that climax behaviour (CB or hatching) in the chick, Gallus domesticus, occurred during episodes of paradoxical sleep (PS). In recent experiments, however, eye opening, a sign of wakefulness, was seen during CB. The present study was designed to decide whether CB is related to PS or wakefulness. Behavioural and polygraphic criteria were employed, and drugs (melatonin and amphetamine) were administered. Melatonin suppressed wakefulness, hatching and PS, but the reappearance of PS did not coincide with that of CB. Amphetamine suppressed PS, but, except for a short period of ataxia, it did not inhibit CB. Lowering of ambient temperature stimulated wakefulness without interfering with CB. Whereas hatching is characterized by vigorous movements, only weak movements could be detected during PS. In view of these findings, it is concluded that CB is related to wakefulness and not to PS. Reports on mammals also indicate that strong movements seen during early stages of development, are not related to PS.