56.    Deficiency of CB1 receptor produces alterations in dendritic fibers in striatum 

INTRODUCTION The cannabinoid receptor type 1 (CB1R) is one of the most abundant G protein-coupled receptors in the Central Nervous System and is presynaptically located in axonal terminals, dendrites and soma. It is widely distributed in the Central Nervous System, both in neurons and glial cells, and has a greater expression in areas such as hippocampus, cerebellum, cerebral cortex, striatum, among others. CB1R is involved in physiological processes such as memory, learning, motor coordination, anxiety and mood. Previous results of our
group showed that hippocampal neurons presented less dendritic and axonal arborization and changes in the synaptic structure. AIMS The aim of this work is to evaluate the axonal and dendritic neuronal cytoskeleton in the Striatum in the absence of CB1R, using cnr1 -/- knockout mice (CB1R -/-). EXPERIMENTAL PROCEDURE Sixty-day-old female and male, CD1 CB1R wild type (CB1R+/+) and CB1R knock-out mice (CB1R-/-) were used in this study. CB1R-/- mice were generated by disruption of the cnr1 gene. Animals were fixed by intracardiac perfusion with 4% (w/v) parafolmaldehyde in 0.1M phosphate buffer (PB) pH 7.4 and post-fixed for 4h in the same solution. Coronal sections of the brains were cut with a vibratome (40μm thick) and stored in 50% (v/v) glycerol solution at -20°C until use. Immunohistochemistry was performed with primary antibodies: mouse anti-Syn (1:1000); mouse anti-MAP-2 (1:1000); mouse anti- NF160 (1:1000); mouse anti- NF200 (1:1000). In order to evaluate MAP-2, NF160+ and NF200+ fibers, the total area of the immunolabeled fibers was related to the total area of the corresponding microscopic field (20x primary magnification), rendering a relative area parameter. The intensity of Syn immunoreactivity was evaluated by means of a relative optical density (ROD). RESULTS MAP2 is a protein expressed in neuronal dendrites. We observed significant decrease in female CB1R-/- mice when compared with female CB1R+/+ mice and male CB1R-/- mice (p<0,001). NF 160 and NF200 are intermediate filaments presents in axons. No differences were observed in NF160 expression in any groups. NF200 only showed significant decrease in female CB1R-/- mice when compared with male CB1R-/- mice (p<0,01). Syn is a protein presented in synaptic vesicles. Both female and male CB1R-/- mice showed a decreased in Syn expression when compared with female and male CB1R+/+ mice (p<0,01 and p<0,05, respectively). We also observed a decrease in female CB1-/- mice when compared with male CB1R-/- mice (p<0,05). CONCLUSIONS The absence of CB1R induces neuronal morphology alterations (less dendritic arborization and synaptic proteins), principally in female mice. These changes could demonstrate that CB1R is implicated in neuronal plasticity. UBACYT 20020130100258BA (AB), UBACYT 20020130300033BA (LC), PIP CONICET 00269 (AB).