Research Report Residual effects of focal brain ischaemia upon cannabinoid CB 1 receptor density and functionality in female rats Maria Luisa Rojo a , Ingegerd Söderström b , Christopher J. Fowler a, ⁎ a Department of Pharmacology and Clinical Neuroscience, Medicine, Umeå University, SE-901 87 Umeå, Sweden b Department of Public Health and Clinical Medicine, Medicine, Umeå University, SE-901 87 Umeå, Sweden ARTICLE INFO ABSTRACT Article history: Accepted 1 December 2010 Available online 8 December 2010 Ischaemic insult results in short-term changes in cannabinoid-1 (CB 1 ) receptor expression in the brain, but it is not known whether long-term changes occur, which could potentially mean a change in the intrinsic ability of the brain to withstand new ischaemic episodes. In this study, we have investigated the expression and functionality of CB 1 receptors in coronal brain slices obtained from ovariectomised female rats 46 days after middle cerebral artery occlusion (MCAO). The animals were treated with either 17ß-oestradiol or placebo pellets 6 h after MCAO and thereafter housed either in isolated or enriched environments. [ 3 H] CP55,940 autoradiography indicated no significant effect of 17ß-oestradiol treatment or housing environment upon CB 1 receptor densities. There was, however, a modest but significant decrease in the CB 1 receptor density on the ipsilateral side relative to the contralateral side in the frontal cortex, parietal cortex, CA1–CA3 regions of the hippocampus, thalamus and hypothalamus. CB 1 receptor functionality was assessed by measurement of basal and CP55,940-stimulated [ 35 S]GTPγS autoradiography. In the frontal cortex, parietal cortex, CA1–CA3 regions of the hippocampus and dentate gyrus, a robust stimulation, blocked by the CB 1 receptor inverse agonist AM251, was seen. There were no significant changes in the response to CP55,940 with respect either to the 17ß-oestradiol treatment, housing environment or MCAO. Our results reveal that although there are modest long-term decreases in ipsilateral CB 1 receptor densities following MCAO in female rats, these decreases do not result in a functional CB 1 receptor deficit. © 2010 Elsevier B.V. All rights reserved. Keywords: Cannabinoid Middle cerebral artery occlusion Ischaemia Stroke Receptor reserve [ 35 S]GTPγS autoradiography CP55,940 1. Introduction Cannabinoid CB 1 receptors are G-protein coupled receptors present in high concentrations in the brain and which are involved in a number of physiological and behavioural events such as regulation of appetite, pain, motor function, body temperature as well as the psychotropic effects sought after by recreational users of cannabis (review see Breivogel and BRAIN RESEARCH 1373 (2011) 195 – 201 ⁎ Corresponding author. Fax: +46 90 785 2752. E-mail address: cf@pharm.umu.se (C.J. Fowler). Abbreviations: AM251, N-(Piperidin-1-yl)-5-(4-iodophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1-H-pyrazole-3-carboxamide; CA1–CA3, cornu ammonis 1–cornu ammonis 3 pyramidal cell layer; CB, cannabinoid; CP55,940, (-)-cis-3-[2-hydroxy-4-(1,1-dimethylheptyl) phenyl]-trans-4-(3-hydroxypropyl)cyclohexanol; Enr, enriched environment; Est, 17ß-oestradiol; GTPγS, guanosine 5′-[γ-thio]triphos- phate; Iso, isolated environment; MCAO, middle cerebral artery occlusion; Pl, placebo; WIN55,212-2, (R)-(+)-[2,3-dihydro-5-methyl-3- (4-morpholinylmethyl)- pyrrolo[1,2,3-de]-1,4-benzoxazin-6-yl]-1-naphthalenylmethanone mesylate 0006-8993/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.brainres.2010.12.001 available at www.sciencedirect.com www.elsevier.com/locate/brainres