Research Report Parallel anxiolytic-like and antinociceptive actions of diazepam in the anterior basolateral amygdala and dorsal periaqueductal gray Guadalupe Jiménez-Velázquez, Francisco Javier López-Muñoz, Alonso Fernández-Guasti ⁎ Departamento de Farmacobiología, Centro de Investigación y de Estudios Avanzados-Sede Sur, Calz. de los Tenorios 235, Col. Granjas Coapa, C.P. 14330, México D.F., Mexico ARTICLE INFO ABSTRACT Article history: Accepted 5 June 2010 Available online 18 June 2010 Rationale: The antinociceptive actions of diazepam and other benzodiazepines are partly due to their anxiolytic-like properties. Objective: This study was conducted to analyze the relationship between the anxiolytic-like and antinociceptive effects of diazepam when injected into the anterior basolateral amygdala (ABLA) and the dorsal periaqueductal gray (dPAG). These areas were selected because of their important participation in the regulation of anxiety and defensive responses. Methods: The anxiolytic-like effect of diazepam was evaluated with the rat burying behaviour test. The pain-induced functional impairment in the rat (PIFIR) model was used to study the effects of diazepam on nociception. Nociception was induced by intra-articular injection of 15% uric acid into the knee joint of the right hind limb. Results: Sole exposure to the burying behaviour test produced a slight non-significant hyperalgesic effect. Diazepam injection (2.0 μg/0.4 μl) into the ABLA or dPAG produced a reduction in cumulative burying behaviour – an anxiolytic-like effect – together with an increase in burying behaviour latency. Such reduced experimental anxiety was paralleled by an antinociceptive response (i.e., increased use of the uric-acid-injected limb). Reduced experimental anxiety was correlated with antinociception after diazepam infusion into both brain structures. Conclusions: Diazepam-reduced experimental anxiety was paralleled by antinociceptive effects. © 2010 Elsevier B.V. All rights reserved. Keywords: Diazepam Anterior basolateral amygdala Dorsal periaqueductal gray Rat defensive burying behaviour Pain-induced functional impairment in the rat (PIFIR) Anxiety–nociception relationship 1. Introduction Diazepam is a benzodiazepine commonly used for treating anxiety (Gries et al., 2005). This benzodiazepine is also employed for the management of several specific painful states; such as: chronic or acute pain associated with anxiety, pain due to muscle injury and spasm or neuropathic pain (Reddy and Patt, 1994). Although diazepam is used in BRAIN RESEARCH 1349 (2010) 11 – 20 ⁎ Corresponding author. Departamento de Farmacobiología, Cinvestav-Sede Sur, Calz. de los Tenorios 235, Col. Granjas Coapa, México D.F., C.P. 14330, Mexico. Fax: +52 5483 28 63. E-mail address: jfernand@cinvestav.mx (A. Fernández-Guasti). Abbreviations: ABLA, anterior basolateral amygdala; dPAG, dorsal periaqueductal gray; PIFIR, pain-induced functional impairment model in the rat; %FI, functionality index percent; AUC, area under the curve 0006-8993/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.brainres.2010.06.014 available at www.sciencedirect.com www.elsevier.com/locate/brainres