Stereotactic coordinates for intracerebroventricular infusion after permanent focal cerebral ischemia in Wistar rats

Abstract

Background: Intracerebroventricular (ICV) experimental route is highly promising due to immediate approach of a "therapy" to the cerebrospinal compartment. Ischemic edema causes structural dislocations and stereotaxia alterations after temporary Middle Cerebral Artery Occlusion (t-MCAO), while there is no similar study for intracerebroventricular (ICV) invasion after permanent MCAO (p-MCAO).

Methods: Male Wistar rats were subjected to right p-MCAO and clinically evaluated 6 and 18 hours post-occlusion, using the modified Neurological Stroke Scale (mNSS) and modified Bederson's Scale (mBS). Infarction volume, hemispheric edema, middle line dislocation and stereotaxia of the lateral ventricles were studied at the same time-points.

Results: P-MCAO induced mild but significant changes in the stereotaxia of the infarcted (ipsilateral) lateral ventricle on 18- (P<0.05), though not 6-hours (P>0.05) post-occlusion. These changes correlated with the mNSS and mBS scores (P<0.01) and allowed the expression of linear mathematical equations (stereotaxic coordinate = b0 + b1*mNSS; calculated by regression analysis) predicting the new ventricular position in each individual animal. The contralateral ventricular system was structurally unaffected on both time-points. Verification experiments indicated that the new coordinates were necessary on 18-hours post-occlusion for successful ICV invasion in all p-MCAO rats (Number Needed to Treat 2.28), compared to 56.25% success when using the classical coordinates for normal rats.

Conclusion: P-MCAO causes relatively late but predictable stereotaxia shifts for ICV invasion, which are different compared to t-MCAO.

Keywords: edema; intraventricular stereotaxic coordinates; lateral ventricles; permanent middle cerebral artery occlusion; stroke; transplantation.

Figure 1. Scatterplots of the mNSS scores to the ML shifts at the levels -0.12 (A1, A2, A3, A4) and -1.08mm (B1, B2, B3, B4) from bregma as well as to the AP shifts (C1, C2, C3, C4), at 6 (upper panel) and 18 hours (lower panel) post MCAO. Insert tables 1a, 1b, 1c, 1d present the corresponding formulae used for calculation of the new stereotaxic coordinates; "nc" indicates no correlation with the mNSS, i.e. no change from the classical coordinates for normal rats [17]. The right ventricle (right panel) is significantly affected at 18-hours and laterally displaced leftwards (A4, B4); the left ventricle (left panel) is displaced milder and not correlated to mNSS (A3, B3). At 6-hours, the entire ventricular system is virtually not affected (A1-C1 and A2-C2).

Figure 2. The corresponding Paxinos atlas' plates (with permission from "The rat brain in stereotaxic coordinates", Paxinos G. and Watson C., figures 34, 42 and 50; copyright Elsevier Academic Press 2005) and the representative brain TTC-stained sections at the levels -0.12 (B, C, D), -1.08 (F, G, H) and -2.04mm (J, K, L) from bregma. Blue traces on the TTC sections (arrows) indicate the track and final position of the stereotaxic needle. Naïve animals (group N) did not need any correction of the Paxinos coordinates (B, F). On 6-hours, the classical coordinates (uncorrected) were sufficient enough for invasion in the lateral ventricles of p-MCAO animals (subgroup Av) (C, G). On 18-hours (subgroup Bv), the new (corrected) coordinates were needed to successfully reach the targeted ventricle in p-MCAO animals (D, H).