opioid theory:-

short peptides secreted from CNS and GIT and...

opioid peptides:-

• endorphin
• encephalins
• dynorphin
• Endomorphine

✓✓Depend on (descending tracts)

👉 it involves encephalin secreting neurons in the
reticular formation.
👉 starting from the PAG (periaqueductal grey area)
of the midbrain.
👉ending in the NRM (nucleus raphe magnus) of the medulla.
👉 from their ending in the substantia gelatinosa of
the dorsal horn.

☑️ in the subtantia gelatinosa:-
enkephalin secreting neuron is involved in presynaptic inhibition of the pain impulse transmission by blocking substance P release.

✓✓Activation of opiate receptors at the interneuronal level produces hyperpolarization of the neurons, which result in the inhibition of firing and the release of substance P, a neurotransmitter involved in pain transmission, thereby blocking pain transmission.

★ Simply:- used in analgesic effect ( relief the pain)