ALPHA-ADRENOCEPTOR SUBTYPE & CL CURRENT IN PAROTID ACINI

唾液的功能重要性在口干症患者中显而易见，口干症患者缺乏唾液会导致舌头和粘膜疼痛；味觉和发音问题、吞咽、咀嚼、牙齿腐烂和脱落；口腔微生物过度生长的风险增加。唾液分泌的生理调节源于供应腮腺的神经释放去甲肾上腺素，进而激活腮腺腺泡细胞上的α-1肾上腺素受体(α1-AR)，引起液体和电解质的分泌。α1-AR介导的液体分泌是通过开放受体激活的依赖于钙离子的氯离子通道来实现的。导致依赖钙离子的氯通道激活和液体分泌的α1-AR亚型尚不清楚。本研究将确定激活新鲜分离的大鼠腮腺单个细胞中钙依赖的氯离子通道的α1-AR亚型。使用膜片钳技术的穿孔膜片结构将测量全细胞钙依赖的氯电流的α1-AR激活。在5-甲基乌拉地尔、WB-4101和哌唑嗪存在和不存在的情况下，全细胞钙依赖的氯-电流的α1-AR激活将被用来确定与氯-外流和液体分泌相耦合的α1-AR亚型。这些药物是竞争性拮抗剂，有助于区分已知存在于腮腺腺泡细胞上的α1-AR亚型。我们将测量羟甲唑啉、环氮唑啉和二甲基咪唑啉对α1-AR诱导的全细胞钙依赖氯电流的激活作用。这些咪唑啉激动剂将被用来获得关于不同程度的受体激活的氯电流所需的药物结构的信息。α1-AR是否调节Na+-K+泵的活性将用膜片钳技术来测量其净外向电流。还将确定调节Na+-K+泵活性的α1-AR亚型。本研究将加深我们对α1-AR在腮腺液体分泌调节中的生理作用的认识，并可能为设计选择性治疗口干症的药物提供合理的依据。

The functional importance of saliva is apparent in patients with xerostomia where lack of saliva results in painful tongue and mucosa; problems with taste and phonation, swallowing, chewing, tooth decay and loss; and increased risk of microbial overgrowth in the oral cavity. Physiologic regulation of salivation results from release of norepinephrine from nerves supplying the parotid gland, which subsequently activates alpha-1 adrenoceptors (alpha1-AR) on parotid acinar cells causing fluid and electrolyte secretion. Alpha1-AR mediated fluid secretion results from the opening of receptor activated Ca2+-dependent Cl- channels. The alpha1-AR subtype causing activation of Ca2+-dependent Cl- channels and fluid secretion is unknown. This study will determine the alpha1-AR subtype that activates Ca2+-dependent Cl- channels in freshly dissociated single cells from rat parotid glands. Alpha1-AR activation of whole-cell Ca2+-dependent Cl- currents will be measured using the perforated-patch configuration of the patch-clamp technique. Alpha1-AR activation of whole-cell Ca2+-dependent Cl- currents in the presence and absence of 5-methylurapidil, WB-4101, and prazosin will be used to determine the alpha1-AR subtype coupled to Cl- efflux and fluid secretion. These drugs are competitive antagonists which are useful in distinguishing the alpha1-AR subtypes known to be present on parotid acinar cells. The effects of oxymetazoline, cirazoline, and xylometazoline in stimulating alpha1-AR induced activation of whole-cell Ca2+-dependent Cl- currents will be measured. These imidazoline agonists will be used to obtain information about the required drug structures needed for varying degrees of receptor-activated Cl- current. Whether or not alpha1-AR modulate Na+-K+ pump activity will be examined using the patch-clamp technique to measure its net outward current. The alpha1-AR subtype modulating Na+-K+ pump activity will also be determined. The present study will add to our understanding of the physiological role of alpha1-AR in regulating fluid secretion in the parotid gland and may provide a rational basis for the design of drugs selective for treating xerostomia.