Possible Interaction: Dietary Fiber and Morphine

“Postischemic licking was not affected by chemical depletion of sensory C-fibers, but it was inhibited by morphine , which has been shown to inhibit the C- and Aδ-fiber –evoked responses of dorsal horn neurons.”

“By contrast, the A fibre evoked responses of the neurones were only slightly reduced by morphine and both the tactile responses and receptive field size to innocuous stimuli enhanced for certain cells.”

“ Morphine selectively reduced the C fibre and pinch evoked activity in a dose‐dependent naloxone‐reversible manner with an ED50 of 7 nmoles.”

“7 It is concluded that morphine and enkephalin inhibit the release of ACh and a non‐cholinergic transmitter from fibres of the myenteric plexus, and that this may involve a hyperpolarization of presynaptic fibres.”

“The numbers of action potentials evoked by excitation of C fibres were depressed by analgesic doses of morphine (1-4 mg/kg i.v.).”

“… C fibres … morphine : (b) the post-effects observed after cessation of conditioning stimuli were dose-dependently (P less than 0.01) diminished; (c) DNIC of responses … diminished by morphine (P less than 0.01); and (e) these effects were specific since they were antagonized by the opiate antagonist, naloxone.”

“In the rat, for instance, the response of dorsal horn cells to C fibre is depressed in a naloxone-reversible and dosedependent fashion by morphine ; in direct contrast, responses to Aa fibre stimulation is poorly affected 11.”

“Intravenous morphine depressed the activation of ascending axons from afferent C fibres (0.5 mg/kg) more markedly than that from afferent Aδ fibres (2 mg/kg), but did not modify the depression of ascending activity produced by PAG stimulation.”

“3 Morphine (0.3 to 1.0 mg/kg) reduced the excitation of neurones by C fibre afferents and also reduced the increase produced by blocking conduction in the spinal cord.”

“Small amounts of morphine (0.1–2.0 mg/kg or 15–80 nA) and met-enkephalin (15–80 nA) produced an increase in the threshold for antidromic activation of these sural fibres.”