Analysis of the influence of 5-HT and GABA neurotransmission of the dorsal raphe nucleus on the defensive behavior induced by the electrical stimulation of the dPAG in morphine withdrawn-rats

• Grant number: 09/15721-0
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: April 01, 2010
• End date: December 31, 2010
• Field of knowledge: Humanities - Psychology - Physiological Psychology
• Principal Investigator: Manoel Jorge Nobre Do Espirito Santo
• Grantee: Kaynara Maria Chenini Motta
• Host Institution: Faculdade de Filosofia, Letras e Ciências Humanas (FFLCH). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

Withdrawal from morphine sensitizes the dorsal periaqueductal gray (dPAG) neurons, as revealed by the intense Fos protein expression as well as the significant decrease observed in the thresholds of electrical stimulation of this structure in rats. Moreover, it is also known that this region, together with the superior and inferior colliculi and raphe nuclei, is involved in the integration of defensive reaction to aversive stimuli that naturally produce fear. The activation of this system evokes characteristics behavioral, autonomic and sensory responses, similar to those that arise in animals facing several aversive stimuli commonly encountered in the natural environment. This type of response keeps a great resemblance to many of the symptoms observed in abstinent individuals. In addition, it is known that acute morphine administration increases the synthesis of serotonin, its release and its rate of renewal. Conversely, abstinence after chronic exposure critically reduces the levels of serotonin in many brain regions. This reduction could then be the basis on which sits the well-known subjective and somatic symptoms commonly observed in both humans and laboratory animals abstinent from opioids. In this way, this experiment aims to study the effects of modulation of serotonergic and GABAergic neurons of the dorsal raphe nucleus on emotional reactivity induced by electrical stimulation of the dPAG in morphine withdrawn-rats previously selected for their high or low emotional reactivity (high or low anxious). (AU)