Distribution of CB2 receptors in adult rat retina.

LÓPEZ EM., TAGLIAFERRO AP., ONAIVI E., LÓPEZ-COSTA JJ.

Buzios, Brasil.

Congreso; Ist IBRO/LARC Congress of Neurosciences of Latin America, the Caribbean and Iberian Peninsula.; 2008

International Brain Organization (IBRO), Sociedad Argentina de Investigación en Neurociencias (SAN), y otras sociedades latinoamericanas de neurociencia

Objectives: Cannabinoid effects are mediated through two receptors, CB1 and CB2, while CB1 is expressed in brain and peripheral tissues, CB2 is expressed in peripheral and immune tissues. However, recent evidences have shown that CB2 is also expressed in central nervous system (CNS)(1). Similarly, in the retina CB1 has been reported in bipolar cells, gabaergic amacrine cells, horizontal cells and inner plexiform layer but CB2 localization seems to be elusive. There is only one report of CB2 receptor mRNA localization by using RT-PCR which has shown the localization of this receptor in photoreceptors, inner nuclear layer and ganglion cell layer (2). The aim of this work was to localize CB2 receptor in the rat retina by using immunocytochemistry. Methods: Male Sprague Dawley rats were anesthetized, their eyes were removed, fixed by immersion in 4 % paraformaldehyde solution and were cryoprotected in 30 % sucrose solution. Cryostat sections were processed by immunocytochemistry using a CB2 rabbit polyclonal antibody. Results: Our results showed that CB2 was localized in the inner retina. Immunoreactive horizontal and amacrine cells were observed in inner nuclear layer. Immunolabeling was also observed in inner plexiform layer and strong labeled cells were detected in ganglion cell layer. Conclusions: These results are in agreement with RT-PCR results that showed CB2 mRNA in the retina and provide further evidence of the presence of CB2 in CNS. Further work is being carried out in our laboratory in order to know the changes of CB2 receptor after light induced degeneration. Future studies will clarify the physiological and pathological roles of this cannabinoid receptor in the retina but certainly this discovery opens a new target for future treatments of retinal diseases.