A study on the effects of 5-HT and GABA modulation of the periaqueductal gray neurons on the affective and somatic disturbances induced by morphine withdrawal

• Grant number: 09/15711-4
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: June 01, 2010
• End date: December 31, 2010
• Field of knowledge: Humanities - Psychology - Physiological Psychology
• Principal Investigator: Manoel Jorge Nobre Do Espirito Santo
• Grantee: Natalia Fernanda de Oliveira Barradas
• Host Institution: Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto (FFCLRP). Universidade de São Paulo (USP). Ribeirão Preto , SP, Brazil

Abstract

It has been demonstrated that drug dependence and addiction is mainly a function of the positive and negative reinforcing effects of these substances, been one of the main reasons they are taken. Their long-term ingestion, however, produces certain type of physiological an pharmacological "accommodation" of central nervous system resulting, in turn, on the emergence of internal processes that counteract the effects of the drug. In this condition, the interruption of chronic ingestion produces a homeostatic imbalance which is manifested in the expression of the various symptoms observed during withdrawal. These symptoms can be divided into physical and affective and their variety is a function of several factors such as type of substance ingested, frequency and duration of treatment, dose, personal and family history, stress resistance, and so on. The inability to cope with negative emotional states, generated by the absence of the drug in the body, is a strong factor that leads to relapse, as demonstrated in both humans and laboratory animals. Withdrawal from drugs of abuse have a feature of an unconditioned stressor and, as such, may also be under the influence of neuronal systems and brain areas that often modulate the body's response to stimuli unconditioned fear. Given the unconditional nature of the response, as a mere presentation of the unconditioned stimulus, or contextual cues that signal the presence of drugs, has the ability to produce physical and emotional withdrawal, among them high levels of anxiety, we suggest that chronic ingestion of opioids can alter the basic circuitry of the brainstem areas that often modulate the unconditioned responses of fear and anxiety that these regions being in compliance with an adaptive role, remained almost unchanged during the evolutionary process. (AU)