Intrathecal morphine slows gastrointestinal transit in rats

Area of Science:

• Pharmacology
• Neuroscience
• Gastroenterology

Background:

• Opioid analgesics like morphine are known to affect gastrointestinal motility.
• The precise site of action for morphine's effects on gastrointestinal transit is not fully elucidated.

Purpose of the Study:

• To investigate the role of the spinal cord in mediating the gastrointestinal inhibitory effects of morphine.
• To compare the effects of intrathecal versus intraperitoneal morphine administration on gastrointestinal transit.

Main Methods:

• Rats received intrathecal or intraperitoneal injections of morphine at varying doses.
• Gastrointestinal transit was measured following morphine administration.
• Naloxone, an opioid antagonist, was administered intrathecally prior to morphine to assess the involvement of spinal receptors.

Main Results:

• Both intrathecal and intraperitoneal morphine administration produced a dose-dependent inhibition of gastrointestinal transit in rats.
• Intrathecal naloxone pretreatment successfully reversed the inhibitory effects of intrathecal morphine.
• However, intrathecal naloxone did not affect the gastrointestinal inhibitory response to intraperitoneal morphine.

Conclusions:

• The spinal cord is a significant site for the gastrointestinal inhibitory effects of intrathecally administered morphine.
• These findings suggest that the central nervous system, specifically the spinal cord, plays a crucial role in mediating morphine's impact on gut motility.