Question

Identify three mechanisms that opiates can exert inhibitory effects on pain transmission within the spinal cord. For each mechanism, provide the location on the cell and way in which inhibition is mediated

Answer 1

Opioids binds to opioids receptors present in central and peripheral nervous system   and acts as pain relievers.
The main receptors of opioids are mU which is present on presynaptic and postsynatic membrane and kappa receptors present on postsynaptic membrane of c fibres which inhibit synaptic neurotransmission of pain.
The opioid receptors are coupled to inhibitory G proteins which inhibit adenylate cyclase. This results in following :

1. Inhibition of adenylate cyclase results in decreased cAMP

2. decreased cAMP results in reduced calcium influx at presynaptic membrane

3. reduced release of neurotransmitter from presynaptic membrane

4. increased efflux of potassium from postsynaptic membrane and increased hyperpolarisation at postsynaptic membrane

These mechanisms results in blockage of pain transmiss