4 Features of DND were distributed evenly throughout the CA1 subfield in both hemispheres in all groups of gerbils. Nicardipine, lidoflazine and flunarizine, but not nimodipine, were protective. This protection extended linearly throughout the hippocampus without altering the pattern of neuronal damage. 5 Compared to saline-treated (78.3 + 2.9% DND) and nimodipine-treated (76.5 + 3.4% DND) gerbils, the overall protection afforded by nicardipine (41.8 + 3.8% DND) was statistically significant. The effects of lidoflazine (53.6 + 7.1%) and flunarizine (55.8 ± 3.9% DND) were of borderline significance. 6 Abnormal neurones appeared in normal and sham-operated brains to the extent of 4.5 + 1.0% and 4.6 + 0.4%, respectively. Such changes can be attributed to fixation artefacts. 7 The results demonstrate that overall protection is conferred on ischaemic hippocampal CA1 neurones by nicardipine and to a lesser extent by flunarizine and lidoflazine, but not by nimodipine.

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.

The objective of this study was to evaluate the broad neurocytoprotective potential of the novel sodium‐calcium ion channel modulator, lifarizine (RS‐87476), in two rodent 72 h survival models of forebrain ischaemia. Under fluothane anaesthesia, rats were subjected to 10 min four vessel occlusion and gerbils to either (i) 5 or (ii) 10 min bilateral carotid artery occlusion. Rats were dosed parenterally solely post‐ischaemia (reperfusion) in a series of five studies covering a range of intra‐arterial/intraperitoneal (i.a./i.p.) combination doses from 2/10, 5/20, 20/100, 50/200 and 100/500 μ kg−1, where the initial loading dose was injected i.a. at 5 min. An i.p. dose was given at 15 min and repeated twice daily. In a sixth study, treatment at 50/200 μg kg−1 was deferred for 1 h. Gerbils were treated (i) 15 min pre‐ischaemia with either (a) 250, (b) 500 μg kg−1 i.p., or (c) 5 mg kg−1 by gavage (p.o.) for 3 days then at 1 h pre‐ischaemia. Animals treated as (ii) received 500 μg kg i.p. 15 min pre‐ischaemia. The above doses were repeated twice daily for 3 days post‐ischaemia for the respective groups. In rats, the protective effect of lifarizine was regionally and cumulatively assessed in six brain regions (anterior and posterior neocortex, hippocampal CA1 subfield, thalamus, striatum, cerebellar Purkinje cells‐brain stem) at each dose level. Cumulative (total) mean ± s.e.mean neurohistopathological scores (0–4) of 1.16±0.09 (n = 5), 1.02±0.10 (n = 5), 0.93±0.06 (n = 6), 0.79±0.09 (n = 9) and 0.45±0.16 (n = 7), respectively, were obtained for the above treatment groups compared to the control (2.01 ±0.17, n =16) group (P< 0.0035). The score for the 1 h deferred treatment group was also significant at 0.77 ±0.10, n = 5 (P< 0.0035). The normal group without ischaemia showed a score of 0.52 ±0.09 (n = 6). In gerbils, (i) percentage delayed neuronal death (DND) of hippocampal pyramidal cells in the CA1 subfield was prevented at 250 (a) and 500 μg kg−1 i.p. (b) (27.2±14.6, n = 6 and 26.9±10.4%, n =10 respectively, P<0.02) compared to controls (78.3 ±8.5%, n = 12) and by 5 mg kg−1 p.o. (c) (2.9±0.8%, n =11, P< 0.002). Mean ± s.e.mean total brain scores (0–4) for each of 4 different features denoting cerebral ‘oedema’ were lower for normal brains (1.60 ±0.34, n = 6) and reduced in animals dosed at 250 (a) (3.00±0.79, n = 6) and 500 μg kg−1 i.p. (b) (3.75±0.36, n =10) compared to controls (6.58±1.00, n =12) (P< 0.02‐0.03). There was a linear relationship (r = 0.97) between the ‘oedema’ scores and percentage CA1 DND. Percentage CA1 DND in response to 10 min ischaemia (ii) was reduced (53.0±21.0%, n = 6, P<0.05) compared to controls (100.0±0.0%, n = 1). The significant neuroprotection shown by lifarizine in rodents substantiates findings in other species. These observations, together with its effect on ion channels and efficacy at extremely low doses offers novelty and suggests a broad spectrum of activity in ischaemia.

1 In a dog model of partial myocardial ischaemia, superimposed ST segment elevations in epicardial ECGs were inhibited by nicardipine over a cumulative i.v. dose range of 1-20 ,ug kg-1. 2 Over the cumulative i.v. dose range of 0.5-166.5 ,ug kg-', nicardipine had little overall effect on gross cardiac conduction, at spontaneous heart rate. 3 Dogs that received oral 1-2 mg kg-1 nicardipine daily for 16 weeks and then survived 1 week occlusion of the left anterior descending coronary artery (LAD) developed a superior coronary collateral circulation compared with untreated animals. 4 Nicardipine given by three different dosing schedules to baboons markedly limited myocardial infarction over a 6 h period of LAD occlusion. 5 Compared with a group of completely untreated dogs, there was protection of the myocardium in the animals given nicardipine that survived 3 months occlusion of the LAD.