Localization of Cb1 Receptors in Rat’s Periaqueductal Gray after Immobilization Stress and Effects of Peptide Tyr-w-mif- 1. Immunocytochemical Study

Address for correspondence: Lina Malinova Department of Anatomy, Histology and Embryology Medical University of Sofia 2 Zdrave Str, Sofia, Bulgaria tel.: 02/ 9172608 e-mail: [email protected] circuits taking part in the stress-induced analgesia (4). Stress activates neural systems that inhibit pain sensation. This adaptive response depends on neuronal pathways that project from the cortical neurons to the midbrain periaqueductal gray (PAG) and descend to the brainstem rostro-ventro-medial medulla and dorsal horn of the spinal cord and suppresses nociception (8,20). The CB1 receptor expression was detected in regions influencing a number of key functions, including mood, motor coordination, autonomic function, memory, sensation, cognition and stress. Electron microscopy studies demonstrated CB1 receptors predominantly on presynaptic terminals (11,15) but they were found also on postsynaptic structures and glia (3). They activate G-proteins that inhibit adenylate cyclase and calcium channels ABSTRACT