Relationship between lateral hypothalamus and melatonin-induced reduction of wakefulness in rats and the receptor mechanism / 中华麻醉学杂志

ABSTRACT

Objective:To investigate the relationship between lateral hypothalamus and melatonin-induced reduction of wakefulness in rats and the receptor mechanism.Methods:Forty clean-grade adult male Sprague-Dawley rats, weighing 250-300 g, were divided into 4 groups ( n=10 each) using a random number table method: control group (group C), melatonin group (group M), melatonin type-1/2 receptor (MT 1R) antagonist luzindole plus melatonin group (group L+ M), and melatonin type-2 receptor (MT 2R) antagonist 4P-PDOT plus melatonin group (P+ M group). In group C, 0.5 μl of 0.9% NaCl solution was microinjected into the lateral hypothalamus.In group M, 1 μmol/L melatonin 0.5 μl was microinjected into the lateral hypothalamus.In group L+ M, 1 μmol/L MT 1/2R and 1 μmol/L melatonin (0.5 μl in total) was microinjected into the lateral hypothalamus.The microinjection time was from 19: 30 to 20: 00.The changes in sleep-wake duration and the oscillating energy in different frequency bands of electroencephalogram were detected by using electroencephalogram and electromyogram recording technology. Results:Compared with group C, the percentage of wakefulness time was significantly decreased, the percentage of non-rapid eye movement sleep and rapid eye movement sleep time was increased, the energy for delta oscillation was increased, the energy for theta oscillation was decreased, and no significant change was found in the energy for alpha oscillation in M and P+ M groups ( P<0.01), and no significant change was found in the parameters mentioned above in group L+ M ( P>0.05). Compared with group M, the percentage of wakefulness time was significantly increased, the percentage of non-rapid eye movement sleep and rapid eye movement sleep time was decreased, the energy for delta oscillation was decreased, and the energy for theta oscillation was increased in group L+ M ( P<0.01), and no significant change was found in the parameters mentioned above in group P+ M ( P>0.05). Conclusion:The lateral hypothalamus may be involved in melatonin-induced reduction of wakefulness in rats, and the mechanism may be related to activating MT 1R in the lateral hypothalamus.