Bellavía S L, Gallará R V
Cátedras de Química Biológica, Facultades de Odontología y Ciencias Médicas, Universidad Nacional de Córdoba, Argentina.
Arch Oral Biol. 1998 Dec;43(12):933-9. doi: 10.1016/s0003-9969(98)00084-3.
In man, the rate of resting salivary secretion can be influenced by environmental stimuli related to light dark cycles or by noxious stimuli (stressors) of psychological origin. The sympathetic branch of the autonomic nervous system and the adrenal medulla play an important part in homeostatic responses. Previous observations have shown that chronic exposure of rats to constant light promotes degranulation of parotid acini and desensitization of submandibular beta-adrenergic receptors. Now the submandibular secretory response elicited by beta- and alpha2-adrenergic agonists was studied in rats chronically exposed to environmental conditions that modified the activities of sympathetic efferents to the pineal, salivary and adrenal glands. Adult male rats were exposed to constant light (LL) or constant darkness (DD) for 20 days, or to stress (2 h daily immobilization) for 14 days. Control animals were kept under the usual lighting conditions and without immobilization. Dose response curves to isoproterenol (i.v), before and after administration (i.v.) of a dose (20 microg/kg) of clonidine were obtained. Beta-adrenergic desensitization was observed in all the experimental groups, while alpha2-adrenergic desensitization was only observed in the stress and LL groups. The results suggest that circulating catecholamines could mediate light and stress effects on submandibular beta-adrenergic secretory responses. Extrasynaptic alpha2-adrenoceptors might modulate the submandibular secretory response when predictable environmental stimuli (daily light phase) or unpredictable stressors raise the concentrations of circulating catecholamines.
在人类中，静息唾液分泌速率可受与昼夜节律相关的环境刺激或心理源性有害刺激（应激源）的影响。自主神经系统的交感神经分支和肾上腺髓质在稳态反应中起重要作用。先前的观察表明，大鼠长期暴露于持续光照下会促进腮腺腺泡脱颗粒和下颌下β-肾上腺素能受体脱敏。现在，研究了在长期暴露于改变了松果体、唾液腺和肾上腺交感传出神经活动的环境条件下的大鼠中，β-和α2-肾上腺素能激动剂引发的下颌下分泌反应。成年雄性大鼠暴露于持续光照（LL）或持续黑暗（DD）20天，或暴露于应激（每天固定2小时）14天。对照动物保持在通常的光照条件下且不进行固定。在静脉注射一剂（20微克/千克）可乐定前后，获得对异丙肾上腺素（静脉注射）的剂量反应曲线。在所有实验组中均观察到β-肾上腺素能脱敏，而仅在应激组和LL组中观察到α2-肾上腺素能脱敏。结果表明，循环儿茶酚胺可能介导光照和应激对下颌下β-肾上腺素能分泌反应的影响。当可预测的环境刺激（每日光照期）或不可预测的应激源提高循环儿茶酚胺浓度时，突触外α2-肾上腺素能受体可能调节下颌下分泌反应。
