RESUMO
To study the effect of antiserotonin drug methysergide on the serotonin and secretagogues on gastric acid secretion in younger and older age animals. Setting: The study was conducted at the pharmacology department, Basic Medical Science Institute, Jinnah Postgraduate Medical Centre, Karachi. Pylorus ligated rate stomach preparation was done on 48 hours starved animals. Drugs were administered, 4 hours latter on rat was sacrified. After opening abdomen, oesophagus was ligated and stomach removed. Contents of stomach were flushed with 3ml distilled water. The contents were used to determine the volume of gastric juice and free and total acidity by titration. Result: Methysergide significantly blocked the gastric inhibitory action for serotonin in the presence of histamine and bethanechol and values were found increased in older animals than younger. But when secretagogue was pentagastrin icnreased values were insigificantly found in older animal against younger. The effect of methysergide, serotonin, histamine and bethanechol on gastric juice volume and acidity is according to parietal cell mass which increases with advancement of age of animals. While pentagastrin's stimulatory action in the presence of serotonin and its antagonist is insignificantly higher in older animals