Ramesh V, Kumar V M
Department of Physiology, All India Institute of Medical Sciences, New Delhi.
Neuroscience. 1998 Aug;85(3):807-17. doi: 10.1016/s0306-4522(97)00663-5.
The study was conducted on 48 free-moving male rats to find out the role of the medial preoptic alpha2 receptors in the regulation of sleep and body temperature. Recording electrodes for assessment of sleep-wakefulness, and injector cannulae for injection of drugs in the medial preoptic area were chronically fixed on the skulls of the animals. The noradrenergic fibres projecting to the medial preoptic area were destroyed in 24 rats by administration of 6-hydroxydopamine at the ventral noradrenergic bundle. Though arousal was produced in normal rats by the injection of the alpha2 adrenergic agonist, clonidine, at the medial preoptic area, it induced sedation in rats with noradrenergic fibre lesion. Clonidine did not alter the rectal temperature in normal rats but it induced hypothermia in lesioned rats. Injection of alpha2 antagonist, yohimbine, at the medial preoptic area induced sleep in rats with intact noradrenergic fibres. However, the sleep inducing effect of this drug was very much attenuated in the lesioned animals. There was no significant change in body temperature, in both these groups of animals, after yohimbine administration. The study indicates the role of presynaptic alpha2 adrenergic receptors in arousal response and indirectly supports the contention that the alpha1 postsynaptic receptors at the medial preoptic area are involved in hypnogenesis. It also suggests that the thermal changes induced by adrenergic system are mediated through alpha1 postsynaptic receptors. But the thermal changes do not contribute towards the induced alterations in sleep-wakefulness. It is proposed that there should be separate sets of noradrenergic terminals for regulation of sleep and body temperature.
本研究以48只自由活动的雄性大鼠为对象，旨在探究内侧视前区α2受体在睡眠和体温调节中的作用。用于评估睡眠-觉醒状态的记录电极以及用于在内侧视前区注射药物的注射套管被长期固定在动物颅骨上。通过在腹侧去甲肾上腺素能束注射6-羟基多巴胺，破坏了24只大鼠投射至内侧视前区的去甲肾上腺素能纤维。虽然在内侧视前区注射α2肾上腺素能激动剂可乐定可使正常大鼠产生觉醒，但在去甲肾上腺素能纤维损伤的大鼠中却诱导了镇静作用。可乐定对正常大鼠的直肠温度无影响，但在损伤大鼠中却诱导了体温过低。在内侧视前区注射α2拮抗剂育亨宾可使去甲肾上腺素能纤维完整的大鼠入睡。然而，该药物的促睡眠作用在损伤动物中大大减弱。给予育亨宾后，这两组动物的体温均无显著变化。该研究表明突触前α2肾上腺素能受体在觉醒反应中的作用，并间接支持了内侧视前区的α1突触后受体参与催眠作用的观点。这也表明肾上腺素能系统诱导的体温变化是通过α1突触后受体介导的。但体温变化对睡眠-觉醒状态的诱导改变并无贡献。研究提出，应该存在独立的去甲肾上腺素能终末组来分别调节睡眠和体温。
