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Neuroprotection in retinal experimental work consists primarily of preventing retinal ganglion cell (RGC) loss after exposure to a hostile event. We have studied the neuroprotective effect on RGCs in an ischemia-reperfusion model by activation of the cannabinoid receptor CB1 using topical application of WIN 55212-2. Intraocular pressure (IOP) was increased by continuous infusion of phosphate buffer saline (PBS) into the anterior chamber of the eye. Mean intraocular pressure was increased up to 88.5 ± 0.29 mm Hg (control normal IOP 15.1 ± 0.25 mm Hg), for 35 min. Animals were distributed in 3 groups. Left eyes underwent acute rise in intraocular pressure. First group was treated with topical Tocrisolve™ 100 in both eyes. Second group was treated with 1% solution of CB1 agonist WIN 55212-2 in both eyes. Third group was treated with WIN 55212-2 1% and CB1 antagonist AM 251 1% solutions in both eyes. Subsequently, RGCs were immunolabeled with Brn3a and automated quantification of retinal mosaics of RGCs were performed. The ischemic damage led to a mean loss in RGC density of 12.33%. After topic administration of WIN 55212-2, mean loss of RGCs was of 2.45%. Co-treatment with CB1 antagonist AM 251 abolished almost completely the neuroprotective effect of WIN 55212-2. Topic 1% WIN 55212-2 showed a neuroprotective effect on RGC degeneration after ischemia-reperfusion without pre-activation of CB1 receptors. [ABSTRACT FROM AUTHOR]

Abstract: Spinal cord injury (SCI) pain exhibits many symptoms associated with peripheral neuropathic pain, including increased tactile hypersensitivity. One novel approach to ameliorate SCI pain is the use of cannabinoid (CB) ligands. The current study evaluated the efficacy of the nonselective CB receptor agonist WIN 55,212-2 on tactile hypersensitivity in rats following a brief compression to the thoracic spinal cord. The withdrawal thresholds of the hind paws following SCI were significantly decreased, indicating tactile hypersensitivity. Systemic injection of WIN 55,212-2 increased withdrawal thresholds in a dose-dependent manner. Pretreatment with the CB1 receptor subtype-selective antagonist AM 251 completely abolished the antinociceptive effect of WIN 55,212-2 whereas pretreatment with the CB2 receptor subtype-selective antagonist AM 630 did not alter the antinociceptive effect of WIN 55,212-2. These data indicate that a CB1-selective agonist may be novel therapeutic treatment for clinical SCI pain. [Copyright &y& Elsevier]