Central L-ornithine, but not polyamines, induces a hypnotic effect in neonatal chicks under acute stress.

To clarify whether L-ornithine and/or its metabolite involves sedative and hypnotic effects under social separation stress, the effects of intracerebroventricular (i.c.v.) injection of L-ornithine and polyamines (putrescine, spermidine and spermine) were compared in chicks. Birds were injected i.c.v. with 0.5 mumol of L-ornithine, putrescine, spermidine, spermine or saline (control). After injection, chicks were immediately separated from the flock and monitored for the number of distress vocalizations and various postures. L-Ornithine greatly attenuated the stress response and caused sedative and hypnotic effects. Among the polyamines, only putrescine attenuated distress vocalizations but did not induce sleep. In conclusion, the sedative and hypnotic effect of L-ornithine was mainly induced by L-ornithine itself, while the polyamines contributed to the sedative, but not hypnotic, effect under social separation stress.

Central L-alanine reduces energy expenditure with a hypnotic effect under an acute stressful condition in neonatal chicks.

Recently, we reported that intracerebroventricular (i.c.v.) injection of L-alanine attenuated the stress response under an acute stressful condition in chicks. However, no information of L-alanine was available for the influence on energy expenditure and changes in the posture under stressful conditions. The purpose of the present study was to clarify whether central L-alanine affects heat production (HP) of neonatal chicks, and whether HP is correlated with the behavior after isolation-induced stress. The i.c.v. injection of L-alanine (0.8 micromol) decreased oxygen consumption, carbon dioxide production and HP shortly after injection. Central L-alanine reduced the posture for active wakefulness, but increased the posture for sitting motionless with head drooped (sleeping posture). The present study demonstrates that central L-alanine decreases energy expenditure and causes a hypnotic effect in chicks exposed to an acute stressful condition.

Intracerebroventricular injection of L-aspartic acid and L-asparagine induces sedative effects under an acute stressful condition in neonatal chicks.

The present study was conducted to clarify the central functions of L-aspartic acid (Asp) and L-asparagine (Asn) during an acute stressful condition in chicks. Intracerebroventricular (i.c.v.) injection of Asp and Asn (0.84 micromol) attenuated the vocalization that normally occurs during social separation stress. Asp decreased the time spent in active wakefulness and induced sedation. Asn had a similar effect to Asp, although somewhat weaker. However, i.c.v. injection of Asp and Asn further enhanced plasma corticosterone release under social separation stress. Taken together, the i.c.v. injection of Asp and Asn has sedative effects under an acute stressful condition, which does not involve the hypothalamic-pituitary-adrenal axis.