BACKGROUND Among the H2 receptor antagonists, Cimetidine promotes healing of peptic ulcer and reduces ulcer pain, but produces a few significant side effects-gynaecomastia, galactorrhoea, etc. H1 antagonists and H2 agonists suppress prolactin release in suckled mother, while H1 agonists and H2 antagonists release prolactin in non-suckled mother. The relationship between H2 receptor inhibitory and H1 receptor stimulant for the raise or decrease of serum prolactin level and also for involvement of third ventricle in hypothalamus area is to be investigated. MATERIALS AND METHODS The present study was to ascertain the site of action of Cimetidine for the raised serum prolactin, whether peripheral action or central action. Therefore, the route of administration of the H2 receptor antagonist Cimetidine was chosen as intravenous and intracerebroventricular respectively. Finally, serum prolactin level was estimated by drawing blood from the ear vein of the experimental animal (Rabbit) every 15 mins, 30 mins and 45 mins respectively. Then, serum prolactin levels were compared and analysed statistically. RESULTS The serum prolactin level was found significantly raised at 15 mins (p < 0.05) and 30 mins (p < 0.001) after the IV Cimetidine. However, there is no significant difference between IV Cimetidine and ICV Cimetidine pre-treated group as Diphenhydramine blocked H1 receptor. CONCLUSION So, it can be concluded that Cimetidine causes raise in serum prolactin level due to its peripheral and central action.
