Deshpande S B
Department of Physiology, Banaras Hindu University, Varanasi, India.
Acta Physiol Scand. 1993 Sep;149(1):51-7. doi: 10.1111/j.1748-1716.1993.tb09591.x.
Gastric fundus strips isolated from lactating, non-lactating and pregnant rats were used to obtain agonist-induced contractions in vitro and the mechanism of alteration in gastric contractility to serotonin during lactation was investigated. The gastric contractile responses to 5-HT expressed as area per unit mass of muscle (cm2 g-1 muscle) were 60-65% greater in lactating rats compared with non-lactating rats. However, responses evoked by acetylcholine (ACh) or histamine were not different. The EC50 values for 5-HT were not different in either group indicating that there was no alteration in the 5-HT affinity for its receptors in lactating rats. In pregnant rats, 5-HT-induced gastric responses were significantly (P < 0.05) lower than those of non-lactating rats. Pretreatment of non-lactating rats with haloperidol (which increases plasma prolactin levels) enhanced the gastric contractile response to 5-HT (P < 0.05). On the other hand bromocriptine administration (which lowers plasma prolactin levels) in lactating or immature rats, decreased the contractile response to 5-HT significantly, while bath application of bromocriptine (0.1 microM) had no effect. Incubation of fundus strips in physiological solution containing prolactin (10 micrograms ml-1) for 24 h decreased the 5-HT evoked contractions, but not the ACh evoked responses. The results in this study indicate that prolactin modulates the intrinsic contractile activity of the gastric smooth muscles to 5-HT.
从哺乳期、非哺乳期和怀孕大鼠分离出胃底条带，用于在体外获得激动剂诱导的收缩，并研究哺乳期胃对5-羟色胺收缩性改变的机制。以每克肌肉的面积（平方厘米·克-1肌肉）表示的胃对5-羟色胺的收缩反应，哺乳期大鼠比非哺乳期大鼠大60%-65%。然而，乙酰胆碱（ACh）或组胺引起的反应没有差异。两组中5-羟色胺的半数有效浓度（EC50）值没有差异，表明哺乳期大鼠中5-羟色胺对其受体的亲和力没有改变。在怀孕大鼠中，5-羟色胺诱导的胃反应显著低于非哺乳期大鼠（P<0.05）。用氟哌啶醇（可提高血浆催乳素水平）预处理非哺乳期大鼠，增强了胃对5-羟色胺的收缩反应（P<0.05）。另一方面，在哺乳期或未成熟大鼠中给予溴隐亭（可降低血浆催乳素水平），显著降低了对5-羟色胺的收缩反应，而浴槽中加入溴隐亭（0.1微摩尔）则没有效果。将胃底条带在含有催乳素（10微克·毫升-1）的生理溶液中孵育24小时，可降低5-羟色胺诱发的收缩，但不影响乙酰胆碱诱发的反应。本研究结果表明，催乳素调节胃平滑肌对5-羟色胺的内在收缩活性。
