PHA3801 Lecture Notes - Lecture 14: Substance P, Tramadol, Allodynia
24 Jul 2018
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Opium: latex of unripe poppy pod containing morphine, codeine, thebaine, papaverine etc. Endorphins: released from pituitary gland and hypothalamus into cns, sc and bloodstream (triggered by prolonged exercise, pain, stress). ~400 aa"s, 7 transmembrane domains, all g-protein coupled. All facilitate membrane hyperpolarisation (k outflow) stabilizes membranes. All inhibit ca channel opening (nt release). -receptors most analgesic effects of o"s + some unwanted effects (e. g. respiratory depression, euphoria, sedation + dependence). Delta-receptor periphery but contribute to analgesia. K-receptors contribute to analgesia at sc level + may elicit sedation + dysphoria. Delta -receptors not true d-receptors, are site of action of certain psychomimetic drugs (w which some opiod"s interact) Presynaptic (relevant for analgesia mu and delta. On nociceptive fibres (relevant for analgesia, but only expressed after injury) mu. Mu receptor: supraspinal analgesia, miosis, euphoria, respiratory depression, nausea, vomiting, constipation, urinary retention, physical dependence. Mu-2 receptor: mediate spinal analgesic actions also respiratory depression, gi actions, cvs effects.
