On the effect of calcium antagonists on cerebral blood flow in rats. A comparison of nimodipine and flunarizine

Comparison of intrathecal flunarizine and nimodipine treatments in cerebral vasospasm after experimental subarachnoid hemorrhage in rabbits

BACKGROUND

the aim of this study was to assess and to compare the ability of intrathecal flunarizine and nimodipine to prevent vasospasm in a rabbit model of subarachnoid hemorrhage (SAH).

METHOD

forty male New Zealand white rabbits were allocated into 5 groups randomly. The treatment groups were as follows: (1) control (no SAH [n = 8]), (2) SAH only (n = 8), (3) SAH plus vehicle (n = 8), (4) SAH plus nimodipine (n = 8), and (5) SAH plus flunarizine (n = 8). Before sacrifice, all animals underwent femoral artery catheterization procedure by open surgery under anesthesia and angiography performed for each animal.

FINDINGS

there was a statistically significant difference between the mean basilar artery cross-sectional areas and the mean arterial wall thickness measurements of the control and SAH-only groups (p < 0.05). Basilar artery vessel diameter and luminal section areas in group 4 were significantly higher than in group 2 (p < 0.05). Basilar artery vessel diameter and basilar artery luminal section areas in group 5 were significantly higher than in group 2 (p < 0.05).Basilar artery vessel diameter and basilar artery luminal section areas in group 5 were significantly higher than in group 4 (p < 0.05).

CONCLUSIONS

these findings demonstrate that flunarizine has marked vasodilatatory effect in an experimental model of SAH in rabbits.

Vasodilator effects of flunarizine on retinal blood vessels in anesthetized rats

The aim of this study was to investigate the effects of intravenous administration of flunarizine on the diameter of retinal blood vessels and blood pressure in anesthetized rats and to compare the effects of this antagonist with those of nicardipine and nifedipine. Retinal vascular images were captured with a fundus camera system for small animals and the diameter of retinal blood vessels contained in the images was measured using image-processing softwares on a personal computer. Blood pressure was continuously measured. Flunarizine [1-30 microg/kg, intravenously (i.v.)] dose-dependently increased the diameter of retinal blood vessels without significantly changing systemic blood pressure. Nicardipine (1-30 microg/kg, i.v.) increased the retinal blood vessel diameter but decreased blood pressure in a dose-dependent manner. Nifedipine (10-100 microg/kg, i.v.) failed to dilate the retinal blood vessels, although it produced comparable depressor responses as those to nicardipine. These results suggest that flunarizine selectively acts on the retinal blood vessels rather than on the peripheral resistance vessels. Flunarizine could therefore be considered as a candidate for therapeutic drugs to treat diseases associated with disorders of retinal circulation without severe cardiovascular side-effects.

PROTECTION OF BLOOD-BRAIN BARRIER BREAKDOWN BY NIFEDIPINE IN ADRENALINE-INDUCED ACUTE HYPERTENSION

The question of whether influxes of ionic Ca+2 into cerebral endothelium plays an important role in increased vascular permeability consequent to an acute hypertension is not accurately resolved. We tested the effect of nifedipine, a calcium entry blocker, on the cerebrovascular permeability for proteins in adrenalin-induced acute hypertension. The experiments were carried out on male Wistar rats. The experimental groups consisted of normotensive saline controls, adrenaline-induced hypertensive rats, and adrenalin-induced hypertensive rats as pre-treated or post-treated with a bolus of nifedipine. Brains of hypertensive rats showed increased permeability to Evans Blue-Albumin complex, when blood pressure elevated rapidly to more than 170 mmHg. The number and size of areas of Evans-Blue extravasation were smaller if an increase in blood pressure was prevented. The short lasting elevation of blood pressure did not result in protein extravasation in brains of hypertensive rats. The results suggest that nifedipine can modify the permeability disruptions observed in acutely hypertensive rats. The data also support the hypothesis that Ca+2 may be responsible for the changes in permeability of BBB in hypertension by mediating the contraction of vascular muscles.

Characteristics of the formation of chronic fatigue syndrome and approaches to its treatment in young patients with focal brain damage

Chronic fatigue is among the manifestations of focal brain lesions. It is most often encountered in multiple sclerosis (MS) and patients with the sequelae of traumatic, inflammatory, and vascular brain damage (encephalopathies). The aim of the present work was to study the mechanisms of formation of this syndrome in 50 patients with focal brain lesions of different origins (in the inactive stage) and to assess the possibility of correcting it using the combined agent Fezam (2 capsules t.i.d. for one month), which contains piracetam and cinarrizine. In patients with encephalopathies, chronic fatigue syndrome was directly associated with the severity of depression. Patients with MS showed changes in the value-sense sphere. Neuropsychological testing showed that the psychological and personality components played a greater role in the origins of chronic fatigue in patients with encephalopathies than in those with MS. Fezam significantly decreased the severity of chronic fatigue, particularly in patients with MS; in the second group (non-MS patients) this was accompanied by a decrease in the severity of depression. Mild side effects (in six patients--12%) consisted generally of sleep disturbances. These results indicate that Fezam should be used in the treatment of chronic fatigue in patients with focal brain lesions; in encephalopathies it should be combined with psychoactive agents.

The effect of nimodipine on cerebral oxygenation in patients with poor-grade subarachnoid hemorrhage

Object. Nimodipine has been shown to improve neurological outcome after subarachnoid hemorrhage (SAH); the mechanism of this improvement, however, is uncertain. In addition, adverse systemic effects such as hypotension have been described. The authors investigated the effect of nimodipine on brain tissue PO2.

Methods. Patients in whom Hunt and Hess Grade IV or V SAH had occurred who underwent aneurysm occlusion and had stable blood pressure were prospectively evaluated using continuous brain tissue PO2 monitoring. Nimodipine (60 mg) was delivered through a nasogastric or Dobhoff tube every 4 hours. Data were obtained from 11 patients and measurements of brain tissue PO2, intracranial pressure (ICP), mean arterial blood pressure (MABP), and cerebral perfusion pressure (CPP) were recorded every 15 minutes.

Nimodipine resulted in a significant reduction in brain tissue PO2 in seven (64%) of 11 patients. The baseline PO2 before nimodipine administration was 38.4 ± 10.9 mm Hg. The baseline MABP and CPP were 90 ± 20 and 84 ± 19 mm Hg, respectively. The greatest reduction in brain tissue PO2 occurred 15 minutes after administration, when the mean pressure was 26.9 ± 7.7 mm Hg (p < 0.05). The PO2 remained suppressed at 30 minutes (27.5 ± 7.7 mm Hg [p < 0.05]) and at 60 minutes (29.7 ± 11.1 mm Hg [p < 0.05]) after nimodipine administration but returned to baseline levels 2 hours later. In the seven patients in whom brain tissue PO2 decreased, other physiological variables such as arterial saturation, end-tidal CO2, heart rate, MABP, ICP, and CPP did not demonstrate any association with the nimodipine-induced reduction in PO2. In four patients PO2 remained stable and none of these patients had a significant increase in brain tissue PO2.

Conclusions. Although nimodipine use is associated with improved outcome following SAH, in some patients it can temporarily reduce brain tissue PO2.