(The) experimental study in serotonin : role of serotonin in gastrointestinal function

의학과/박사[한글] The Experimental Study in Serotonin -Role of Serotonin in Gastrointestinal Function- Kyu Chul, Whang Department of Pharmacology and Surgery Yonsei University, School of Medicine, Seoul, Korea (Director : W.C.Lee, S.S. Hong and K.S. Min) White and Magee (1958) have reported that the continuous intravenous infusion of serotonin increased the secretion of mucin from the pyloric mucosa. Furthermore, they demonstrated that the serotonin effect on mucin secretion was not dependent on an increased motility of the pylorus, because the effect was present also in the everted gastric pouch, and was not abolished by hexamethonium which decreases gastric motility. Gaddum and Picarelli (1957) reported that there are two types of serotonin receptors, namely the M-receptor (nervous) and the D-receptor (smooth muscle) in the guinea pig ileum. The nervous receptor is blocked by morphine or atropine, while the smooth muscle receptor is blocked by dibenzyline or d-lysergic acid diethylamide(LSD) The present study attempts first to clarity the relationship between these receptors and gastric secretion particulary mucus contents and motility, and secondly, to confirm the effect or role of serotonin on dietary induced gastric secretion in dogs. Methods Eight healthy mongrel dogs, weighing 10 to 15 kg, were employed in these experiments. According to the technique described by DeVito and Harkins (1959) we prepared denervated (Heidenhain) pouches in six dogs. In two animals we made we made innervated (Pavlov) pouches using the method of Holland and Jemerin (1938). The dogs were maintained on a semi-fluid rice diet made of 90% starch and 10% protein. They were fasted for 15 hours before ezch experiments. Powdered whole milk was used as the standard food for the stimulation of gastric juice production. The dogs were fed portions containing 200 calories in a solution of, milk powder diluted with distilled water to a volume of 200 ml. Two grams of sidium chloride were added to each 200 ml. In order that the effects of calories and volume might be eliminated in these studies we used other food in an equi-caloric and equi-volumetric basis in some of the animals. The effects of the subcutaneous injection of serotonin, histamine, and other agents on gastic secretion induced by the standard milk preparation were examined. The secretion volume and degree of acidity were determined at thirty minute intervals. The free and total acidity of the gastic juice were measured in 1.0 ml aliquots by titration of the sample with N/20 NaOH, using Tofer's reagent and phenolphthalein as indicators. Total acidity was considered to be a more accurate reflection of the parietal cell secretion than free acidity (Shay et al. 1950). The protein content of the gastric juice (gastric mucin) was also determined by the biuret reaction. After the dogs were anesthetized using pentobarbital, they were prepared for an acute series of testing of a effect of serotinin on the volume and acidity of the gastric secretion by inserting and fixing a Levein tube in the stomach and by ligating the pylorus. In five dogs gastric and duodenal motility and intraluminal water pressures were determined after tubes with attached balloons were passed through a gastrostomy opening into both the stomach and the duodenum. Kymographic recordings were made over periods of several hours. Also, simultaneously, changes in blood pressure and in respiration were recorded. Results Ⅰ. Gastric secretion : In most experiments the Heidenhain pouch dogs showed a spontaneous fasting secretion of 0.5 to 1.0 ml per 3- minutes of a clear viscous fluid which contained practically no free acid, and 0.01 to 0.03 mEq of total acid. Milk stimulated the production of gastric juice. In dogs having the devervated pouch the pattern of response to milk feeding was quite consistent. Secretion lasted about 4 hours with the peak of secretion being reached in the second half hour after feeding. After four hours there was a neglihible output of secretion. Following the subcutaneous administration of histamine, the peak of the gastric secretion was observed in the first half hour, and the output of secretion lasted about two hours. The pattern of response of secretion to the stimulation of milk or of histamine in the Pavlov pouch dogs was quite similar to that seen in the Heidenhain pouch dogs. However the pattern was more uniform in the Heidenhain pouch dogs, In 15 experiments using Heidenhain dogs and 5 experiments using Pavlov dogs the single subcutaneous injection of 0.5-2.0 mg of serotonin produced little change, or even a decrease, in both the volume and degree of acid output. Furthermore, serotonin greatly inhibited the milk=induced secretion in the Heidenhain pouch dogs. This inhibition was absent when histamine was used to stimulate the gastric secretions in the same animals. The continuous intravenous administration of serotonin, at levels of 3-10 ug per kg, 034 minute, was associated with a significant increase in the volume of gastric juice aspirated from three dogs which were anesthetized with pentobarbital. The degree of acidity varied only a little. On the contrary to the serotonin effect, histamine given at dose levels of 0.8 to 3 ug per kg, per minute caused a marked increase both in the volume and in the degree acidity of the gastric juice in these same three animals. Ⅱ. Gastric mucin secretion : There was a significant increase in the mucin content of gastric juice obtained from the Heidenhain pouch following a single subcutaneous injection of 1.0 mg of serotonin. However following the administration of 0.2 mg histamine or of histamine plus 1.0 mg of serotonin, the mucin content was not relatively increased. There was an increase in the total amount of mucin secondary to the increased total volume of the gastric juice. This increase in the total mucin production and in the degree of acid output paralleled the increase in the total gastric secretion volume secondary to the histamine stimulation. In the Heidenhain pouch dogs the stimulation of mucin production following the administration of serotonin was strikingly inhibited by the subcutaneous injection of 1.0 mg of LSD, of 20 mg of 2-bromo-dlysergic acid diethylamide (BOL) or of 50 mg of dibenzyline. The subcutaneous injection of 25 mg of morphine produced a mild inhibition of the serotonin effect of stimulation of mucin production in the gastric juice, 1.0 mg of atropiner or 10 mg of hexamethonium did not block the increased prodution of mucin following serotonin injections. Nevertheless, dibenzyline, LSD, BOL, morphine atropine or hexamethonium alone, did not affect on gastric mucus production. Ⅲ. Gastric motility ; The single administration of 0.5 mg of serotonin produced an immediate increase in gastric and duodenal tonus and motility in the anesthetized dogs. The arterial blood pressure also rapidly increased. A period of apnea was followed by a transient hyperpnea. The increased motility, elicited by the serotonin, usually ceased within 10 minutes, and gastrointestinal motility returned to normal. The effect of several pharmacologic agents in modifying the gastrointestinal response to serotonin was examined. The intravenous administration of 1.0 mg of atropine did not inhibit the serotonin response. Intravenous administration of 10 mg of hexamethonium, or 20 mg of morphine stimulated duodenal motility but had no effect on gastric motility. However, the response of duodenal motility to serotonin was not inhibited by hexamethonium or mirphine. A single intravenous injection of 1.0 mg of LSD caused no response in gastroduodenal motility. Further-more there was no inhibitory action to serotonin induced motility. The intravenous administration of 0.2 mg of histamine did not affect on increased duodenal motility caused by serotonin. However, administration of histamine or serotonin, raisei arterial blood pressure. [영문] White and Magee (1958) have reported that the continuous intravenous infusion of serotonin increased the secretion of mucin from the pyloric mucosa. Furthermore, they demonstrated that the serotonin effect on mucin secretion was not dependent on an increased motility of the pylorus, because the effect was present also in the everted gastric pouch, and was not abolished by hexamethonium which decreases gastric motility. Gaddum and Picarelli (1957) reported that there are two types of serotonin receptors, namely the M-receptor (nervous) and the D-receptor (smooth muscle) in the guinea pig ileum. The nervous receptor is blocked by morphine or atropine, while the smooth muscle receptor is blocked by dibenzyline or d-lysergic acid diethylamide(LSD) The present study attempts first to clarity the relationship between these receptors and gastric secretion particulary mucus contents and motility, and secondly, to confirm the effect or role of serotonin on dietary induced gastric secretion in dogs. Methods Eight healthy mongrel dogs, weighing 10 to 15 kg, were employed in these experiments. According to the technique described by DeVito and Harkins (1959) we prepared denervated (Heidenhain) pouches in six dogs. In two animals we made we made innervated (Pavlov) pouches using the method of Holland and Jemerin (1938). The dogs were maintained on a semi-fluid rice diet made of 90% starch and 10% protein. They were fasted for 15 hours before ezch experiments. Powdered whole milk was used as the standard food for the stimulation of gastric juice production. The dogs were fed portions containing 200 calories in a solution of, milk powder diluted with distilled water to a volume of 200 ml. Two grams of sidium chloride were added to each 200 ml. In order that the effects of calories and volume might be eliminated in these studies we used other food in an equi-caloric and equi-volumetric basis in some of the animals. The effects of the subcutaneous injection of serotonin, histamine, and other agents on gastic secretion induced by the standard milk preparation were examined. The secretion volume and degree of acidity were determined at thirty minute intervals. The free and total acidity of the gastic juice were measured in 1.0 ml aliquots by titration of the sample with N/20 NaOH, using Tofer's reagent and phenolphthalein as indicators. Total acidity was considered to be a more accurate reflection of the parietal cell secretion than free acidity (Shay et al. 1950). The protein content of the gastric juice (gastric mucin) was also determined by the biuret reaction. After the dogs were anesthetized using pentobarbital, they were prepared for an acute series of testing of a effect of serotinin on the volume and acidity of the gastric secretion by inserting and fixing a Levein tube in the stomach and by ligating the pylorus. In five dogs gastric and duodenal motility and intraluminal water pressures were determined after tubes with attached balloons were passed through a gastrostomy opening into both the stomach and the duodenum. Kymographic recordings were made over periods of several hours. Also, simultaneously, changes in blood pressure and in respiration were recorded. Results Ⅰ. Gastric secretion : In most experiments the Heidenhain pouch dogs showed a spontaneous fasting secretion of 0.5 to 1.0 ml per 3- minutes of a clear viscous fluid which contained practically no free acid, and 0.01 to 0.03 mEq of total acid. Milk stimulated the production of gastric juice. In dogs having the devervated pouch the pattern of response to milk feeding was quite consistent. Secretion lasted about 4 hours with the peak of secretion being reached in the second half hour after feeding. After four hours there was a neglihible output of secretion. Following the subcutaneous administration of histamine, the peak of the gastric secretion was observed in the first half hour, and the output of secretion lasted about two hours. The pattern of response of secretion to the stimulation of milk or of histamine in the Pavlov pouch dogs was quite similar to that seen in the Heidenhain pouch dogs. However the pattern was more uniform in the Heidenhain pouch dogs, In 15 experiments using Heidenhain dogs and 5 experiments using Pavlov dogs the single subcutaneous injection of 0.5-2.0 mg of serotonin produced little change, or even a decrease, in both the volume and degree of acid output. Furthermore, serotonin greatly inhibited the milk=induced secretion in the Heidenhain pouch dogs. This inhibition was absent when histamine was used to stimulate the gastric secretions in the same animals. The continuous intravenous administration of serotonin, at levels of 3-10 ug per kg, 034 minute, was associated with a significant increase in the volume of gastric juice aspirated from three dogs which were anesthetized with pentobarbital. The degree of acidity varied only a little. On the contrary to the serotonin effect, histamine given at dose levels of 0.8 to 3 ug per kg, per minute caused a marked increase both in the volume and in the degree acidity of the gastric juice in these same three animals. Ⅱ. Gastric mucin secretion : There was a significant increase in the mucin content of gastric juice obtained from the Heidenhain pouch following a single subcutaneous injection of 1.0 mg of serotonin. However following the administration of 0.2 mg histamine or of histamine plus 1.0 mg of serotonin, the mucin content was not relatively increased. There was an increase in the total amount of mucin secondary to the increased total volume of the gastric juice. This increase in the total mucin production and in the degree of acid output paralleled the increase in the total gastric secretion volume secondary to the histamine stimulation. In the Heidenhain pouch dogs the stimulation of mucin production following the administration of serotonin was strikingly inhibited by the subcutaneous injection of 1.0 mg of LSD, of 20 mg of 2-bromo-dlysergic acid diethylamide (BOL) or of 50 mg of dibenzyline. The subcutaneous injection of 25 mg of morphine produced a mild inhibition of the serotonin effect of stimulation of mucin production in the gastric juice, 1.0 mg of atropiner or 10 mg of hexamethonium did not block the increased prodution of mucin following serotonin injections. Nevertheless, dibenzyline, LSD, BOL, morphine atropine or hexamethonium alone, did not affect on gastric mucus production. Ⅲ. Gastric motility ; The single administration of 0.5 mg of serotonin produced an immediate increase in gastric and duodenal tonus and motility in the anesthetized dogs. The arterial blood pressure also rapidly increased. A period of apnea was followed by a transient hyperpnea. The increased motility, elicited by the serotonin, usually ceased within 10 minutes, and gastrointestinal motility returned to normal. The effect of several pharmacologic agents in modifying the gastrointestinal response to serotonin was examined. The intravenous administration of 1.0 mg of atropine did not inhibit the serotonin response. Intravenous administration of 10 mg of hexamethonium, or 20 mg of morphine stimulated duodenal motility but had no effect on gastric motility. However, the response of duodenal motility to serotonin was not inhibited by hexamethonium or mirphine. A single intravenous injection of 1.0 mg of LSD caused no response in gastroduodenal motility. Further-more there was no inhibitory action to serotonin induced motility. The intravenous administration of 0.2 mg of histamine did not affect on increased duodenal motility caused by serotonin. However, administration of histamine or serotonin, raisei arterial blood pressure.restrictio