Van Den Pol A N, Patrylo P R, Ghosh P K, Gao X B
Department of Neurosurgery, Yale University Medical School, New Haven, Connecticut 06520, USA.
J Comp Neurol. 2001 May 7;433(3):349-63. doi: 10.1002/cne.1144.
Hypocretin is a recently discovered peptide that is synthesized by neurons in the lateral hypothalamic area (LH) and is believed to play a role in sleep regulation, arousal, endocrine control, and food intake. These functions are critical for the development of independent survival. We investigated the developmental profile of the hypocretin system in rats. Northern blot analysis showed that the expression of hypocretin mRNA increased from postnatal day 1 to adulthood. Both of the identified hypocretin receptor mRNAs were strongly expressed very early in hypothalamic development, and expression subsequently decreased in the mature brain. Immunocytochemistry revealed hypocretin-2 peptide expression in the cell bodies of LH neurons and in axons in the brain and spinal cord as early as embryonic day 19. Whole-cell patch clamp recordings from postnatal P1-P14 LH slices demonstrated a robust increase in synaptic activity in all LH neurons tested (n = 20) with a 383% increase in the frequency of spontaneous activity upon hypocretin-2 (1.5 microM) application. A similar increase in activity was found with hypocretin-1 application to LH slices. Hypocretin-2 evoked a robust increase in synaptic activity even on the earliest day tested, the day of birth. Furthermore, voltage-clamp recordings and calcium digital imaging experiments using cultured LH cells revealed that both hypocretin-1 and -2 induced enhancement of neuronal activity occurred as early as synaptic activity was detected. Thus, as in the adult central nervous system, hypocretin exerts a profound excitatory influence on neuronal activity early in development, which might contribute to the development of arousal, sleep regulation, feeding, and endocrine control.
下丘脑泌素是一种最近发现的肽，由下丘脑外侧区（LH）的神经元合成，据信在睡眠调节、觉醒、内分泌控制和食物摄入中发挥作用。这些功能对于独立生存的发展至关重要。我们研究了大鼠下丘脑泌素系统的发育情况。Northern印迹分析表明，下丘脑泌素mRNA的表达从出生后第1天到成年期逐渐增加。已鉴定的两种下丘脑泌素受体mRNA在早期下丘脑发育阶段均强烈表达，随后在成熟大脑中的表达下降。免疫细胞化学显示，早在胚胎第19天，LH神经元的细胞体以及脑和脊髓的轴突中就有下丘脑泌素-2肽表达。对出生后P1 - P14的LH切片进行全细胞膜片钳记录表明，在所测试的所有LH神经元（n = 20）中，突触活性有显著增加，施加下丘脑泌素-2（1.5微摩尔）后自发活动频率增加了383%。对LH切片施加下丘脑泌素-1也发现了类似的活性增加。即使在最早测试的出生当天，下丘脑泌素-2也能引起突触活性的显著增加。此外，使用培养的LH细胞进行的电压钳记录和钙数字成像实验表明，早在检测到突触活性时，下丘脑泌素-1和 -2就诱导了神经元活性的增强。因此，与成年中枢神经系统一样，下丘脑泌素在发育早期对神经元活性产生深远的兴奋性影响，这可能有助于觉醒、睡眠调节、进食和内分泌控制的发育。
