How we change what others think, feel, believe and do
Peptides are short polymers formed of two or more amino acids linked by peptide bonds.
They are produced by from large polypeptides which are broken apart in the right places within the body of the neuron.
Once released, peptides are regulated through destruction by enzymes (there is no reuptake).
Most peptides act as neuromodulators, although some act as neurotransmitters.
Endogenous opioids are a family of peptides that bind with opiate receptors. In contrast, external drugs are known as exogenous opiates. (Note the word difference: 'opiates' are external).
There are three types of opiate receptor: mu, delta and kappa. Opiate receptor stimulation of different neural system leads to analgesia, inhibition of defensive reactions or stimulation of reward.
Enkephalins (or encephalins) are another family about which little is known.
Many vesicules contain both more 'normal' neurotransmitters and peptides. The peptides help regulate sensitivity of receptors to the neurotransmitter.
Opioids have been linked with pleasure sensations of satiation and consummation, including rest, bliss and sedation. Whilst dopamine has been linked with reward, it is now believed that it is more correctly associated with motivation and wanting.
Naloxone is used to reverse opiate intoxication. This drug can also help with other addictions as the opiate system has been implicated in wider experiences of reward.