Opioid Pharmacology fully solved 2023/2024

Opioid PharmacologyOpioid receptor subtypes - correct answer Mu, kappa, delta, (n=nociceptin) Mu, kappa & delta are G-i coupled GCPRs Mu is the predominant receptor Delta, kappa contribute to analgesia at *spinal level* Opioid receptor MOA - correct answer G-i coupled GCPRs - inhibition of AC 1) decrease in VG Ca2+ current (decrease NT release --analgesic effect) 2) increased K+ conductance -- membrane hyperpolarization Distribution of opioid receptors in CNS, PNS - correct answer *Midbrain*: regulation of periacqueductal gray (*PAG*) - mu agonists stimulate *descending inhibitory* neurons, decreased pain transmission from periphery to thalamus (*blocks asecnding pain*) *Spinal cord*: mu in substantia gelatinosa (dorsal horn) -- inhibitory effect on pain transmission *Brainstem*: effect on cough, respiration, N/V, pupil size, vasomotor (BP control) *Hypothalamus*: effect on endocrine regulation, thermoregulation *Limbic system*: mood & behaviour Opioid analgesic effects mostly mediated by these 4 brain structures: - correct answer 1) Dorsal horn of spinal cord 2) PAG matter 3) Thalamus 4) Limbic structures 3 classes of endogenous opioid agonists - correct answer endorphins (beta-endorphins) act on mu enkephalins (leu-, met-) act on detla dynorphins - act on kappa