2.2 Intracerebral hemorrhage (ICH) induction

The collagenase induced cerebral hemorrhage model established by Rosenberg has been widely used [27]. Mouse was anesthetized with chloral hydrate by 10% chloral hydrate solution which was injected intraperitoneally to the animal with a dose of 4 ml/kg body weight in all the experiments. Before operation, the hair on the scalp was removed with electric hair clippers and followed with depilatory cream. An incision of 1.5 mm wide in the scalp was made. The skull periosteum was removed using blunt separation. After mounting the animal to a stereotaxis instrument with ear bars, an injection point of collagenase over the right parietal head region was identified accurately (1.7 mm to the right of and 0.9 mm below the bregma, see Fig. 1(a)). Then a hole of 1 mm in diameter was drilled carefully over the injection point with electric cranial drill. Deep intracerebral hemorrhage was caused by bleeding within the deep structures of the brain (thalamus, basal ganglia, pons, and cerebellum). In this study, ICH was induced by microinjection of collagenase into the basal ganglia. Right after the injection of 0.5 µl of 0.15 U/µl collagenase through the hole in the parietal head region, the hole was sealed with bone wax.

(a) Schematic showing the location of bregma (yellow dot) and collagenase injection point (red dot). (b) Schematic of our PAT system for in vivo monitoring the collagenase induced intracerebral hemorrhage (ICH).