The differential role of specific POMC neuronal circuits in mediating the beneficial and detrimental effects of opioids.

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Morphine-like drugs (opioids) have been used and abused for centuries, mainly for their pain-relieving and rewarding effects. These drugs still remain important treatments for pain, however, they have multiple undesirable side-effects which greatly limit their clinical usefulness. These include sedation, suppression of breathing and rewarding effects which can lead to addiction.Morphine-like drugs work by mimicking the action of chemicals made naturally in the body, called endogenous opioids. The best known of these is beta-endorphin and it has an important role in regulating the pain we experience - especially when we are under stress it can be released to suppress pain perception. This natural release of beta-endorphin does not cause the side effects that are seen with opioid drugs like morphine. This may give us a clue as to how to achieve better pain relief that has reduced side effects.A first step towards this goal is to better understand the function of the brain circuits that release endogenous opioids. This has previously been difficult as beta-endorphin is made in only two small, inaccessible groups of neurons in the brain. However, by using selective genetic engineering techniques we can introduce modified receptors (DREADDs) into the beta-endorphin releasing neurons of genetically engineered mice. This allows us to selectively activate (or inhibit) these neurons by giving an otherwise inactive drug and study the effects on animal behaviour.We will test whether the beta-endorphin neurons in the brainstem can produce an analgesic effect; assess whether this is of use in models of chronic pain and also whether this more natural way of releasing opioids exerts a pain relieving effect that is associated with fewer side effects (we believe that there may be reduced sedation, reward and addictive potential). We will also determine whether the pain relief from stress, feeding and vagal nerve stimulation are produced by the activation of these brainstem beta-endorphin producing neurons.