Rudman D, Chawla R K, Katra B S
Am J Physiol. 1975 Apr;228(4):1245-8. doi: 10.1152/ajplegacy.1975.228.4.1245.
Two or more melanotropic peptides are present in extrahypophyseal regions of mammalian brain. Previous studies showed that extrahypophyseal melanotropic activity is not influenced by hypophysectomy, adrenalectomy, or exogenous glucocorticoid. The present study investigated the possible influence of the following factors on the level of melanotropic activity in whole brain, cerebral cortex, cerebellum, midbrain, and brainstem of mouse and rat: age, sex, starvation; and of the following hormones or drugs administered by the intraperitoneal or intracerebral route: norepinephrine, dihydroxyphenylalanine, pargyline, 6-hydroxy-dopamine, alpha-methyltyrosine methyl ester, reserpine, acetylcholine, pilocarpine, atropine, serotonin, p-chlorophenylalanine, pentobarbital, pentylenetetrazol, insulin, melatonin, and cycloheximide. Only age influenced extrahypophyseal melanotropic activity. The activity per unit of tissue wet weight or of tissue protein increased in all regions progressively from birth to 1 yr of age. Extrahypophyseal melanotropic activities perunit wet weight of tissue at 50 wk averaged 4.3 times those at birth. When brain of adult rodents was fractionated by differential centrifugation, the major proportion of melanotropic activity was recovered in myelin (27-35 percent), nerve endings (20-22 percent), and mitochondria (25-30 percent). The lower activity in newborn brain resulted not onlyfrom absence of a myelin fraction, but also from lower activity at birth in nerve endings and mitochondria.
两种或更多种促黑素肽存在于哺乳动物脑的垂体外区域。先前的研究表明，垂体外促黑素活性不受垂体切除、肾上腺切除或外源性糖皮质激素的影响。本研究调查了以下因素对小鼠和大鼠全脑、大脑皮层、小脑、中脑和脑干中促黑素活性水平的可能影响：年龄、性别、饥饿；以及通过腹腔内或脑内途径给药的以下激素或药物：去甲肾上腺素、二羟基苯丙氨酸、帕吉林、6-羟基多巴胺、α-甲基酪氨酸甲酯、利血平、乙酰胆碱、毛果芸香碱、阿托品、5-羟色胺、对氯苯丙氨酸、戊巴比妥、戊四氮、胰岛素、褪黑素和环己酰亚胺。只有年龄影响垂体外促黑素活性。从出生到1岁，所有区域每单位组织湿重或组织蛋白的活性逐渐增加。50周龄时，单位组织湿重的垂体外促黑素活性平均为出生时的4.3倍。当用差速离心法对成年啮齿动物的脑进行分级分离时，促黑素活性的主要部分在髓磷脂（27%-35%）、神经末梢（20%-22%）和线粒体（25%-30%）中被回收。新生脑活性较低不仅是因为没有髓磷脂部分，还因为出生时神经末梢和线粒体的活性较低。
