Final answer:
Enkephalin is involved in both presynaptic and postsynaptic inhibition, functioning as an endogenous opioid by binding to opioid receptors and reducing pain transmission through both inhibition of neurotransmitter release and neuronal hyperpolarization.
Step-by-step explanation:
Enkephalin is a neuropeptide involved in both presynaptic and postsynaptic inhibition. It can modulate pain perception by inhibiting the release of neurotransmitters, which affects the pain signal as it is being transmitted. Enkephalins are endogenous opioids, meaning they are naturally produced by the body and function similarly to opioid drugs by binding to opioid receptors in the brain and spinal cord.
When enkephalin binds to these receptors, it can prevent the release of substance P, a neurotransmitter associated with pain transmission, leading to presynaptic inhibition. Concurrently, enkephalins cause postsynaptic inhibition by hyperpolarizing the neurons, making them less likely to fire action potentials, thus diminishing the perception of pain. This dual mechanism of action is crucial for the body's ability to modulate pain and reduce the overall experience of pain.