en Physiology Physiology Original Research: Basic Science in Medicine Original Research: Basic Science in Medicine Morphine was used as a remedy for the control of diarrhea centuries before it's sedative-analgesic effect was discovered. Although several mechanisms have been proposed for the morphine-induced inhibition of gastrointestinal transit (OIT), the exact mechanism has not yet been identified. On this basis the possible involvement of the dopaminergic system in morphine-induced inhibition of transit was investigated. This study showed that morphine decreased gastrointestinal transit (OIT) of charcoal dust in mice.in a dose-dependent manner. The response was inhibited by the opiate antagonist naloxone. Pretreatment of animals with the D-2 antagonist sulpiride or the peripheral dopamine antagonist domperidone did not alter the morphine-induced inhibition of OIT. The D-l/D-2 agonist apomorphine also decreased OIT in mice. The response was inhibited by SCH 23390 or sulpiride pretreatment (p<0.01), but not by domperidone or naloxone. It is concluded that morphine and apomorphine inhibit OIT through opiate and dopaminergic mechanisms, respectively. Morphine, Dopamine, Gastrointestinal transit. 133 138 http://mjiri.iums.ac.ir/browse.php?a_code=A-10-298-408&slc_lang=en&sid=1 ZAHRA SARI 20031947532846004653 20031947532846004653 Yes From the Department of Physiology, Arak University of Medical Sciences, Arak MR ZARRINDAST 20031947532846004654 20031947532846004654 No the Department of Pharmacology, Tehran University of Medical Sciences, Tehran F ROUSHANZAMIR 20031947532846004655 20031947532846004655 No the Department of Pharmacology, Shahid Beheshti University of Medical Sciences, Tehran,l R.lran.