Morphine

Mechanism of action

- morphine is naturally derived opiods which acts as central analgesic

- acts on mu,kappa and delta receptors located predominantly in brain.morphine can show both effect i.e; first stimulant and then depressant and its analgesic effect is due to mu receptor

- all three receptor are present at prejunctional neuron and are GPCRs

- binding of opioids agonist leads to activation of GPCR and reduces formation of cAMP,followed by blocking or suppression of Ca⁺² & voltage gated N type channel(mainly kappa receptor) and opens K⁺ channels(mainly through mu and delta receptor). Therefore this results in hyperpolarization and decreases intracellular Ca⁺² concentration, leading to decrement in release of neurotransmitters by cerebral,spinal and myenteric neurons.

Reference: Tripathi K.D., “Essentials of Medical Pharmacology”, Jaypee brothers medical publishers, Seventh edition, New Delhi, page no. 386,479.