Calcium entry blockers protect brain energy metabolism against ischemic damage

Calcium and vitamin D intakes may be positively associated with brain lesions in depressed and nondepressed elders

Studies indicate that diet and vascular calcification may be related to the occurrence of brain lesions, although the importance of dietary calcium and vitamin D has not been investigated. The objective of this study was to test the hypothesis that calcium and vitamin D intakes would be positively associated with brain lesion volumes in elderly individuals with and without late-life depression. A cross-sectional study was performed as part of a longitudinal clinical study of late-life depression. Calcium and vitamin D intakes were assessed in 232 elderly subjects (95 with current or prior depression, 137 without depression) using a Block 1998 food frequency questionnaire. Calcium, vitamin D, and kilojoule intake were determined. Brain lesion volumes were calculated from magnetic resonance imaging scan. Subjects were 60 years or older. Calcium and vitamin D intakes were significantly and positively correlated with brain lesion volume (P < .05 and P < .001, respectively). In 2 separate multivariable models, controlling for age, hypertension, diabetes, heart disease, group (depression/comparison), lesion load (high/low), and total kilocalories, these positive associations remained significant (P < .05 for calcium; P < .001 for vitamin D). In conclusion, calcium and vitamin D consumption were associated with brain lesions in elderly subjects even after controlling for potentially explanatory variables. These associations may be due to vascular calcification or other mechanism. The possibility of adverse effects of high intakes of calcium and vitamin D needs to be further explored in longitudinal studies of elderly subjects.

Veratridine-induced intoxication: an in vitro model for the characterization of anti-ischemic compounds?

Due to the complexity of ischemia-induced cellular dysfunction many different pharmacological approaches have been tested to improve cellular ischemia resistance. However, despite the importance of [Na+]i for ischemia-induced dysfunction, only very few studies have investigated the contribution of the Na+ channel to ischemia-induced failure of intracellular ion homeostasis. Since an activation of Na+ channels by veratridine also results in a failure of intracellular ion homeostasis, the veratridine- and ischemia-induced alterations of cellular function were compared. Moreover, despite the difference in the electrophysiological changes induced by veratridine and ischemia, the possible involvement of a slowly inactivating, less selective Na+ channel in both veratridine- and ischemia-induced cellular dysfunction is discussed. As a conclusion it is suggested that veratridine intoxication could be a helpful in vitro method for the characterization of putative anti-ischemic compounds.

Slow channel inhibitor effects on brain function: tolerance to severe hypoxia in the rat

1. The protective effects of ten slow channel inhibitor drugs against severe progressive hypoxia were investigated in rats breathing spontaneously during light anaesthesia. Respiration, heart rate, electrocorticogram (ECoG) and/or electroencephalogram (EEG) were recorded. 2. Tolerance times were monitored from hypoxia onset until cessation of respiration, ECoG, EEG synchronization, and 'background-EEG'. Drugs were administered i.v. 5 min before the onset of hypoxia. 3. Verapamil, gallopamil, and nimodipine resulted in a significant increase of tolerance times; fendiline and bepridil showed a small increase (not significant); bencyclan and prenylamine were ineffective; cinnarizine and diltiazem slightly reduced tolerance times as did flunarizine at low doses. 4. At protective doses, verapamil, gallopamil, and nimodipine significantly raised the respiration rate but had little or no cardiac depressor effects. Bencyclan showed ventilatory drive but cardiocirculatory depression. A clear-cut ventilatory drive did not occur with the other ineffective slow channel inhibitors. 5. It is suggested that the protective actions observed were not due to slow channel inhibition per se, nor to spasmolytic potency or increased cerebral blood flow. Ventilatory drive associated with other cardiopulmonary actions which secondarily raise the brain oxygen supply are likely to be responsible for this effect.

The influence of the calcium antagonists flunarizine and verapamil on cerebral blood flow and oxygen tension of anesthetized WFS-rats

The beneficial influence of calcium antagonists in restoring the disturbed circulation and metabolism towards its normal level has been described for a variety of circulatory disorders (arteriosclerosis, ischemia, hypertension). To date, however, little information exists concerning the physiological effects of the blocking molecules on cerebral blood flow (CBF) and oxygen tension at the organ surface (sPO2). White rats (Wistar-Frömter strain, N = 56, 180-250 g bw) were anesthetized with ketamine-xylazin, and artificially ventilated until normal acid-base status was achieved. Polarographic multi-wire O2 and H2 electrodes (15 microns diameter, 1 g weight) were balanced on the open brain through a cranial window drilled into the skull-cap in order to perform surface PO2 and hydrogen clearance measurements. Two different calcium antagonists, verapamil and flunarizine, were tested in order to verify structural differences of the molecules. Infusion of verapamil (7.5 micrograms/kg.min) and flunarizine (0.3 mg/kg.min) induced an increase in CBF by 55%/h (verap.) and by 62%/h (flun.) respectively while the controls (infusion of equal amounts of ringer-lactate) remained constant, ranging between 0.5 and 2.7 ml/g.min (n = 25 measurements). Surface PO2 improved distinctly in response to verapamil (39% increase) but was uneffected by flunarizine (less than 1%). Both drugs, however, lowered MAP by 18% (verap.) and by 33% (flun.) respectively probably due to peripheral vasodilatation and to the lowering of heart minute volume. In comparison with flunarizine the small MAP change after verapamil has resulted in the rise in CBF and sPO2.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of cerebroprotective agents on cerebral blood flow and on postischemic energy metabolism in the rat brain

Male Wistar rats were subjected to forebrain ischemia of 10 min duration by clamping both common carotid arteries and simultaneously lowering systemic blood pressure to 40 mm Hg by exsanguination. Recovery was achieved by removing the arterial clamps and reinfusing the blood. Cortical levels of high-energy phosphates and glycolytic substrates were determined enzymatically. Naftidrofuryl (10 or 20 mg/kg i.p.) or ketamine (5 mg/kg i.v.) were applied 30 min prior to the induction of ischemia. S(-)-Emopamil (4 mg/kg) or nimodipine (50 micrograms/kg) were administered by intravenous infusion over 30 min. Nimodipine and emopamil increased the blood glucose level and lowered preischemic blood pressure. Under control conditions, a tendency toward a higher cortical glucose level was observed in treated brains. Brain energy stores were exhausted after ischemia in control and treated animals to the same degree. Lactate levels, however, were higher in emopamil-treated animals. This effect was attributed to the elevated preischemic glucose levels. During the early recovery period, the restoration of high-energy phosphates was accelerated by both calcium entry blockers. Nimodipine and emopamil increased the levels of glucose and glucose-6-phosphate in the early postischemic period. Naftidrofuryl (10 mg/kg) increased the level of creatine-phosphate and ATP after 2 min of recovery. Naftidrofuryl (20 mg/kg) exerted no effect on cerebral energy metabolism, but considerably reduced postischemic blood pressure (possibly thereby masking its ameliorative action). Ketamine accelerated the postischemic restoration of high-energy phosphates. In the conscious rat, local cerebral blood flow (LCBF) was determined with the 14C-iodoantipyrine technique following emopamil (20 mg/kg s.c.) or naftidrofuryl (10 mg/kg i.v.) application.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of calcium entry blocker emopamil on postischemic energy metabolism of the isolated perfused rat brain

The effects of emopamil on postischemic energy metabolism and electroencephalographic (EEG) recovery were investigated in the isolated rat brain perfused at either constant pressure or, alternatively, at constant flow rate. Flow rate and perfusion pressure were monitored continuously. The brains were perfused with a fluorocarbon emulsion for 30 min, and after 30 min of ischemia, perfusion was reinstituted for 5, 30, or 60 min. Global cerebral perfusion rate was increased by emopamil throughout the perfusion period and, accordingly, in brains perfused at a constant flow rate, perfusion pressure was reduced by the drug. At constant pressure perfusion, after 5 min after ischemia, cortical levels of creatine-phosphate, adenosine triphosphate (ATR), glucose, glucose-6-phosphate, and fructose-6-phosphate were higher in emopamil-treated brains than in controls, although the levels of adenosine diphosphate (ADP) and adenosine monophosphate (AMP) were reduced. When brains were perfused at constant flow rate, however, emopamil exhibited no effect on brain energy metabolism in the early reperfusion period. Postischemic restoration of high-energy phosphates proved to depend on the flow rate used. After 30 min of postischemic reperfusion, cortical levels of lactate were lower in emopamil-treated brains compared to controls at both constant pressure and constant volume perfusion. Postischemic lactate levels were independent of flow rate and were also reduced when emopamil was only present during reperfusion. The postischemic restoration of cortical EEG activity was improved by the calcium entry blocker.(ABSTRACT TRUNCATED AT 250 WORDS)