Intracerebral cobalt chloride injection: a new model of focal hypoxic injury?

CALTANA L; LAZAROWSKI A; RAMOS AJ; BRUSCO A

Washington DC, USA

Congreso; 34th Meeting of the Society for Neuroscience; 2005

Society for Neuroscience

INTRACEREBRAL COBALT CHLORIDE INJECTION: A NEW MODEL OF FOCAL HYPOXIC INJURY? Caltana L1, Lazarowski A1, Ramos AJ2 and Brusco A1 1Instituto de Biología Celular y Neurociencia “Prof. E De Robertis” Facultad de Medicina Universidad de Buenos Aires, 2Montreal Neurological Institute, Montreal, Canada,. brusco@fmed.uba.ar Hypoxia is one of the major pathological factors inducing neuronal injury. Cobalt chloride (CoCl(2)) is a synaptic blocker and a potent activator of hypoxia-inducible factor-1. In order to develop an animal model of focal cerebral hypoxia, adult male Wistar rats were anaesthetized, placed in a stereotaxic apparatus and intracerebrally injected with 2 ul of  50 mM CoCl(2). The site of injection, confirmed by histological analysis, was layer 2-3 of right fronto-parietal cortex hemisfere (Bregma –1.30 mm). Five days after the surgery, rats were fixed with 4% w/v paraformaldehyde plus 0.25% v/v glutaraldehyde in 0.1 M phosphate buffer pH 7.4. The cerebral area around the injection was dissected and postfixed with osmium tetroxide, contrasted with uranil acetate and finally embedded in Durcupan resin. Ultrathin sections were stained with lead nitrate, examined in a Zeiss M-9 electron microscope and photographed. The ultrastructural studies showed an inflammatory reaction in the area of injection. Larger intercellular spaces and a disruption of neuronal and glial morphology with thin and extended processes forming an irregular network were observed. In the penumbra zone adjacent to the area of the injection, the tissue structure was more conserved but we observed abundant images of nuclear cleavage, cytoplasmatic multivesicular contents and altered mitochondrial ultrastructure (abnormal crests with swelling images). Typical synaptic contacts are scarce and there were abnormal presynaptic structures as well as lamellar images of membranous processes and profiles included in the matrix between neurons and glial cells. Outside the penumbra limits, the brain tissue presented the typical morphology. Our results suggest that CoCl(2) is able to induce local apoptotic activity in the brain tissue exposed to the drug. The localized damage makes this model really useful to induce a very focal brain injury. Supported by UBACYT grant M-072.