Grant M P, Landis S C
Department of Pharmacology, Case Western Reserve University, School of Medicine, Cleveland, Ohio 44106.
J Neurosci. 1991 Dec;11(12):3772-82. doi: 10.1523/JNEUROSCI.11-12-03772.1991.
During development, the innervation of rat sweat glands undergoes a striking change from noradrenergic to cholinergic function. The acquisition of secretory responsiveness by the glands is temporally correlated with the appearance of cholinergic properties. In addition, responsiveness fails to appear in the absence of innervation. To investigate the basis of the onset of functional transmission and secretory responsiveness and its possible relationship to innervation, we analyzed the development of muscarinic cholinergic receptors in sweat glands, examined their expression in the glands of adult rats sympathectomized at birth, and assayed the ability of muscarinic agonists to increase phosphoinositide (PI) turnover. Autoradiographic and in situ hybridization analysis revealed that muscarinic ligand binding sites were first detectable as glands begin to form on postnatal day 4 (P4). Between P4 and P14, receptor concentration increased in parallel with mRNA for the m3 receptor subtype. On P14, the concentration of ligand binding sites approached adult levels, although only a small proportion of glands at this age secrete in response to nerve stimulation or cholinergic agonists. When the pharmacological properties of muscarinic receptors in sweat glands of adult rats sympathectomized at birth were compared to those of normal glands, the concentration and affinity determined with [N-methyl-3H]-scopolamine and the Ki values determined with the subtype-selective muscarinic antagonists 4-DAMP, pirenzepine, and AF DX-116 were similar. In addition, the molecular subtype was unchanged as was the level of m3 message. Studies of PI turnover in response to muscarinic stimulation indicated that the receptors expressed in sweat glands isolated from sympathectomized and acutely denervated, as well as control, rats were functionally coupled to phospholipase C. The absence of sympathetic innervation therefore does not appear to influence either the development of muscarinic receptors or their coupling to PI turnover. Our results suggest that functional sympathetic cholinergic innervation plays a central role in the development and maintenance of secretory function at a step distal to signal transduction across the cell membrane.
在发育过程中，大鼠汗腺的神经支配经历了从去甲肾上腺素能功能到胆碱能功能的显著转变。腺体获得分泌反应性在时间上与胆碱能特性的出现相关。此外，在没有神经支配的情况下，反应性不会出现。为了研究功能传递和分泌反应性开始的基础及其与神经支配的可能关系，我们分析了汗腺中毒蕈碱型胆碱能受体的发育，检查了它们在出生时进行交感神经切除术的成年大鼠腺体中的表达，并测定了毒蕈碱激动剂增加磷酸肌醇（PI）周转的能力。放射自显影和原位杂交分析表明，随着出生后第4天（P4）腺体开始形成，毒蕈碱配体结合位点首次可检测到。在P4和P14之间，受体浓度与m3受体亚型的mRNA平行增加。在P14时，配体结合位点的浓度接近成年水平，尽管此时只有一小部分腺体对神经刺激或胆碱能激动剂有分泌反应。将出生时进行交感神经切除术的成年大鼠汗腺中毒蕈碱受体的药理学特性与正常腺体的进行比较时，用[N-甲基-3H]-东莨菪碱测定的浓度和亲和力以及用亚型选择性毒蕈碱拮抗剂4-DAMP、哌仑西平和AF DX-116测定的Ki值相似。此外，分子亚型以及m3信息水平均未改变。对毒蕈碱刺激后PI周转的研究表明，从交感神经切除和急性去神经的大鼠以及对照大鼠分离的汗腺中表达的受体在功能上与磷脂酶C偶联。因此，交感神经支配的缺失似乎不会影响毒蕈碱受体的发育或它们与PI周转的偶联。我们的结果表明，功能性交感胆碱能神经支配在细胞膜信号转导远端的分泌功能的发育和维持中起核心作用。
