Stress Induced Reinstatement
In the conditioned place preference paradigm, stress has been shown to reinstate conditioned place preferences in rats after the preference had been extinguished. This has implications for research on addiction because of the effect that stress has on human relapse behavior. Stress induced reinstatement in CPP occurs when the animal is exposed to stress after a place preference has been extinguished. This exposure leads to reinstatement of the place preference. Common stressors used in these paradigms include foot-shock and noise Some studies have shown that when drugs of abuse are used as appetitive stimuli, exposure to stress can reinstate place preference that has been extinguished over two weeks.
When rats experience stress in the form of foot-shock or noise, changes occur in the norepinephrine system and the Hypothalamic-pituitary-adrenal axis. These changes have a high impact on the reinstatement conditioned place preference. Stress stimulates the release of corticotropin-releasing hormone (CRH) from the rat's hypothalamus which leads to a series of changes through the pituitary gland in the brain to release glucocorticoids from the adrenal glands. CRH also stimulates the release of neurotransmitter in the hypothalamic regions of the brain to mediate stress-induced changes in brain activity This system plays a key role in the reinstatement of conditioned place preference. CRH acts as a neurotransmitter in regions of the brain including the bed nucleus of the stria terminalis and the amygdala. Reinstatement of conditioned place preference has shown to be blocked when antagonists for CRH receptors are injected into the BNST. In other words, the effects of stress on reinstatement can be inhibited by blocking the receptor sites for CRH in certain areas of the brain. The neurotrasmitter Noradrenaline also plays a role in stress induced reinstatement. Blockage of certain noradrenergic receptors inhibit stress-induced reinstatement. Furthermore, disinhibition of areas of the brain which inhibit the release or noradrenaline also nullify the effect of stress-induced reinstatement. Together, the noradrenaline and CRH systems play a key role in the stress-induced reinstatement of conditioned place preference and provide knowledge of the neurochemical basis of stress-induced relapse.
Read more about this topic: Conditioned Place Preference, Extinction and Reinstatement Procedures, Reinstatement
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