Pain control at brain level

Content

–Our analegsic system–Opioids :a. Endrophinb. Enkaphlin–Receptors–Mechanism–Areas concerned

Analgesic system • pain has 2 components :

perception & reaction• The degree to which a person

reacts to pain varies tremendously.

• This results partly from a capability of the brain itself to suppress input of pain signals to the nervous system by activating a pain control system called analgesia system

opioids1.Opioids are the main analgesic system in brain 2.They are of 2 types: endorphins & enkephlins 3.Drugs that mimic their effect are called opiates4. Although the opioids have a broad range of effects, their primary use is to relieve intense pain, whether that pain is from surgery or a result of injury or disease such as cancer

opiates :

• Drugs that mimic action of opioids.

Endorphins• The general term endorphins refers

to some endogenous morphine-like substances whose activity has been defined by their ability to bind to opiate receptors in the brain.

• Endorphins(brain polypeptides with actions like opiates) may function as synaptic transmitters or modulators. Endorphins appear to modulate the transmission of pain signals within sensory pathways.

• When injected into animals, endorphins can be analgesic

Enkephalins

• Two closely related polypeptides (pentapeptides) found in the brain that also bind to opiate receptors are

• Methionine enkephalin (met-enkephalin) and leucine enkephalin (leuenkephalin).

• The amino acid sequence of met-enkephalin has been found in alpha-endorphin and beta-endorphin, and that of beta-endorphin has been found in beta-lipotropin, a polypeptide secreted by the anterior pituitary gland

Receptors• The major effects of the

opioids are mediated by three major receptor families.

• These are designated by the Greek letters μ (mu), κ (kappa), and δ (delta).

• Each receptor family exhibits a different specificity for the drug(s) it binds.

Receptors • The analgesic properties of

the opioids are primarily mediated by theμ receptors

• .The enkephalins interact more selectively with the δ receptors in the periphery

• All three opioid receptors are members of the G protein–coupled receptor family and inhibit adenylyl cyclase

mechanism• block neurotransmitter

release by A. inhibiting Ca2+ influx into the presynaptic terminal, B . open potassium channels, which hyperpolarizes neurons and inhibits spike activity. They act on various receptors in the brain and spinal cord..

• So, activation of the analgesia system by nervous signals entering the periaqueductal gray and periventricular areas, or inactivation of pain pathways by morphine-like drugs, can almost totally suppress many pain signals entering through the peripheral nerves.

Areas concerned

 • PGA area: enkephalin• Raphe magnus nucleus :serotonin• Periventricular nuclei in

hypothalamus

• Referneces

Guyton textbook of physiology

www.zuvin.com

www.bioscience.org

www.chemitryexplained.com