Neuroprotective efficacy of lifarizine (RS‐87476) in a simplified rat survival model of 2 vessel occlusion

Abstract

1 A new, modified rat two vessel occlusion model (with hypotension) was established and the neuroprotective efficacy of the novel agent lifarizine (RS-87476) was examined. 2 The two vessel occlusion model used in the study was a modification of the model described in the literature, whereby we have obviated the need to use a muscle relaxant and intubate the trachea to provide ventilatory support by providing a tight fitting face mask attached to the ventilator. Furthermore, the need to combine exsanguination and additional pharmacological means of inducing the mandatory hypotension (50 mmHg), required to decrease brain blood perfusion pressure, has been removed by simply manipulating the concentration of the already present halothane anaesthetic. 3 The appropriate level of hypotension having been reached, microvascular clips were applied to bilaterally occlude the common carotid arteries for 12 min. This resulted in a loss of the cortical EEG activity. Local cerebral blood flow was measured 6 min into the occlusion period, using the fully quantitative ["4C]-iodoantipyrine autoradiographic technique, in a separate group of rats (n = 5). This illustrated the lack of any blood flow, in the areas under study, during the period when there was an isoelectric cortical EEG pattern. 4 The high grade global ischaemic lesion which occurred gave quantifiable neuronal damage in several vulnerable regions of the brain, namely, the hippocampal CA, sub-field, cortex, thalamus, striatum, and cerebellar brain stem (Purkinje cells). 5 Following the global ischaemic insult the rats were allowed to recover for 72 h before assessment of the damage, during which time one group of rats (n = 11) received 100 jig kg-1 lifarizine i.a. 5 min postocclusion, 500 jig kg-' lifarizine i.p. 15 min post-occlusion, and 500 jug kg-' lifarizine i.p. twice daily for 72 h. A second group of rats (n = 12) was treated with appropriate volumes of vehicle (0.4 ml kg-' i.a. and 2 ml kg-' i.p.) at identical time points. 6 Histopathological damage was assessed, from cresyl violet and haematoxyline/eosin stained sections, using a scoring system of 0-6 (no damage -complete neuronal death). The dosing regimen of lifarizine gave reduced damage in the hippocampal CA, sub-field (4.1 0.3 to 2.8 + 0.6) and striatum (1.7 0.3 to 1.2+0.3) and significant neuroprotection in the anterior cortex (2.0+0.2 to 1.2+0.2; P<0.05), thalamus (1.5+0.2 to 0.8+0.2; P<0.01), posterior cortex (1.5±0.2 to 1.0+0.2; P<0.05) and cerebellar brain stem (0.9+0.2 to 0.4+0.1; P<0.01). The overall mean brain score was significantly reduced (from 1.5+0.1 to 0.9+0.2). 7 These data show that the newly modified 2 vessel occlusion model produced a quantifiable level of ischaemic damage and that the novel agent lifarizine is neuroprotective in the model.

Reappearance of Hippocampal CA1 Neurons after Ischemia is Associated with Recovery of Learning and Memory

“…Subtle differences may exist in the methods employed to induce global ischemia. In our study, halothane was used to reduce systemic blood pressure during the time of ischemia (Bendel et al, 2005b;McBean et al, 1995). It can be hypothesized that halothane slows the progression of neuronal degeneration.…”

“…All experiments were approved by the Animal Ethics Committee of Northern Stockholm. We used a recently developed transient global ischemia model (Bendel et al, 2005b) utilizing halothane to reduce systemic blood pressure (McBean et al, 1995). The rats were anaesthetized with halothane (Fluothane s , AstraZeneca, Sö dertälje, Sweden), intubated and ventilated.…”

Overexpression of SOD1 in Transgenic Rats Protects Vulnerable Neurons Against Ischemic Damage After Global Cerebral Ischemia and Reperfusion

“…The brain regions examined were the hippocampus, cortex, thalamus, and striatum. The histopathological damage was measured using a neuropathological scoring system of 0 -6, in which 0 ϭ no damage, 1 ϭ 0 -10%, 2 ϭ 10 -25%, 3 ϭ 25-50%, 4 ϭ 50 -75%, 5 ϭ 75-100%, and 6 ϭ complete neuronal death (McBean et al, 1995). Scores for SOD1 Tg rats were compared with those for the non-Tg littermates by means of a nonparametric analysis using the Mann -Whitney U test.…”

Rat Neonatal Immune Challenge Alters Adult Responses to Cerebral Ischaemia

“…To induce ischaemia, a ventral midline neck incision was made allowing the isolation of the common carotid arteries. Both common carotid arteries were occluded simultaneously for 20 mins with nontraumatic microarterial clips, and the blood pressure reduced to and maintained between 50 and 55 mm Hg for the duration of the surgery by means of fine adjustments of the halothane anaesthesia (McBean et al, 1995;McBean and Kelly, 1998). A 20 mins duration of carotid artery occlusion was identified in preliminary trials as necessary and sufficient to produce consistent neuronal cell damage in the CA1 region of the hippocampus, one region particularly vulnerable in global ischaemia (Pulsinelli et al, 1982;Smith et al, 1984a;Colbourne et al, 1999).…”