Centrally mediated intestinal stimulation by morphine

Area of Science:

• Neurogastroenterology
• Pharmacology

Background:

• The central nervous system influences gastrointestinal motility.
• Opioid receptors in the brain can modulate gut activity.

Purpose of the Study:

• To investigate the effects of central administration of morphine, apomorphine, and epinephrine on feline small intestinal electrical activity.
• To determine if central opioid-induced gut effects are mediated by the emetic pathway.

Main Methods:

• Adult cats were surgically implanted with electrodes along the small intestine and a cannula into the cerebral ventricle.
• Drugs (morphine, apomorphine, epinephrine, naloxone) were administered intraventricularly (i.vt.) or intraperitoneally (i.p.).
• Small intestinal spike potentials were recorded and analyzed.

Main Results:

• Intraventricular morphine significantly increased spike potentials in the proximal small intestine.
• This effect was abolished by intraventricular naloxone, indicating central opioid receptor involvement.
• Apomorphine and epinephrine, potent emetic agents, did not alter intestinal activity when given centrally.

Conclusions:

• Central administration of morphine enhances small intestinal activity through a naloxone-sensitive, central mechanism.
• This effect is independent of the central emetic pathways activated by apomorphine and epinephrine.