Abstract
The effect of morphine on the ascending excitatory reflex of the circular muscle elicited by radial distension of the gut wall was studied in the isolated guinea-pig small intestine. A three compartment bath, in which an intermediate compartment divided the site of intraluminal stimulation (caudal compartment) from the site of reflex contraction recording (oral compartment), was used. Morphine (0.01-10 μM) applied independently to each compartment, caused a concentration-dependent depression (up to 90%) of the amplitude of distension-evoked reflex contractions. Concentration-response curves to morphine were shifted to the right by naloxone (30 nM) with an apparent pA2 value of about 8.5, which suggests an interaction with opioid μ-receptor subtypes. Our results indicate that morphine not only depressed transmission from excitatory motor neurons to the circular muscle but also neuro-neuronal transmission along the ascending excitatory reflex pathway.
Original language | English |
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Pages (from-to) | 195-198 |
Number of pages | 4 |
Journal | Neuroscience letters |
Volume | 144 |
Issue number | 1-2 |
DOIs | |
Publication status | Published - 14 Sept 1992 |
Keywords
- Ascending excitatory reflex
- Guinea pig ileum
- Morphine
- Naloxone
- Opioid μ-receptor subtype