We have studied the metabolic and functional effects of two new platelet-activating factor (PAF) antagonists (BN 50726 and BN 50739) and their diluent (dimethyl sulfoxide; DMSO) during reoxygenation of the 14-min ischemic isolated brain. Blood gases, EEG, auditory evoked potentials, cerebral metabolic rate for glucose (CMRglc), and cerebral metabolic rate for oxygen (CMRO2) were monitored throughout the study. Frozen brain samples were taken for measurement of brain tissue high-energy phosphates, carbohydrate content, and thiobarbituric acid-reactive material (TBAR, an indicator of lipid peroxidation) at the end of the study. Following 60 min of reoxygenation in the nontreated 14-min ischemic brains, lactate, AMP, creatine (Cr), intracellular hydrogen ion concentration [H+]i), and TBAR values were significantly higher and ATP, creatine phosphate (PCr), CMRglc, CMRO2, and energy charge (EC) values were significantly lower than the corresponding normoxic control values. PCr and CMRO2 values were significantly higher, and glycogen, AMP, and [H+]i values were significantly lower in the BN 50726-treated ischemic brains than in DMSO-treated ischemic brains. In brains treated with BN 50739, ATP, ADP, PCr, CMRO2, and EC values were significantly higher, and lactate, AMP, Cr, and [H+]i values were significantly lower than corresponding values in the DMSO-treated ischemic brains. TBAR values were near control levels in all brains exposed to DMSO. There was also marked recovery of EEG and auditory evoked potentials in brains treated with DMSO. Treatment with BN 50726 or BN 50739 in DMSO appeared to improve brain mitochondrial function and energy metabolism partly as the result of DMSO action as a free radical scavenger.(ABSTRACT TRUNCATED AT 250 WORDS)

The cerebral vascular effects of various adrenomimetic agents were examined in 12 isolated canine brains perfused with blood at constant flow. Changes in cerebral vascular resistance (CVR) and the magnitude of pressor or depressor responses observed following drug injection were examined. The presence of alpha adrenergic receptors in this vascular bed is indicated by the increased CVR observed when phenylephrine, norepinephrine, and epinephrine were administered and by the reduced or reversed pressor actions of these compounds following treatment with the alpha adrenergic blocking drug phenoxybenzamine HCl. The presence of beta adrenergic receptors in this vascular bed is indicated by the decreased CVR noted when isoproterenol was given and by the reduced depressor actions of this compound following treatment with the beta adrenergic blocking drug propranolol. Further evidence for the presence of beta adrenergic receptors is demonstrated by the vasomotor reversal to epinephrine which was observed following alpha suppression with phenoxybenzamine. As catecholamine blood levels in intact dogs are low in comparison to those achieved in these studies, it appears doubtful that circulating catecholamines play an important physiological role in the regulation of CVR. Possible explanations are considered for the lower response of the cerebral vasculature to catecholamines when this response is compared to that observed in other vascular beds.

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Changes in the free fatty acid pool size and fatty acyl chain composition of mitochondrial membrane phospholipids and their relation to disruption of mitochondrial function were examined in rat brains after 30 min of cerebral ischemia (Pulsinelli‐Brierley model) and 60 min of normoxic reoxygenation. During ischemia, significant hydrolysis of polyunsaturated molecular species from diacyl phosphatidylcholine, particularly fatty acyl 20:4 (arachidonic acid; 20% decrease) and 22:6 (docosahexaenoic acid; 15% decrease), was observed. Thirty minutes of ischemia caused a 16% loss of 18:2 (linoleic acid) from phosphatidylethanolamine. Recirculation for 60 min did not return the polyunsaturated fatty acid content of phospholipids to normal. Total content of free fatty acids increased during ischemia, particularly 18:2 and 22:6, which exhibited the most dramatic rise. The free fatty acid pool size continued to increase during 60 min of recirculation. The respiratory control ratio decreased significantly during 30 min of ischemia with no apparent recovery following 60 min of reoxygenation. The degree of free radical‐mediated lipid peroxidation in mitochondria was significantly increased during ischemia and reperfusion. It was concluded that (a) 30 min of cerebral ischemia caused differential degradation in each of the phospholipid classes and preferential hydrolysis of the polyunsaturated molecular species and (b) 60 min of normoxic reperfusion failed to promote reacylation of the mitochondrial phospholipids and restoration of normal respiration.

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The inorganic phosphate (Pi) NMR peak in brain has an irregular shape, which suggests that it represents more than a single homogeneous pool of Pi. To test the ability of the Marquardt‐Levenberg (M‐L) nonlinear curve fit algorithm software (Peak‐Fit) to separate multiple peaks, locate peak centers, and estimate peak heights, we studied simulated Pi spectra with defined peak centers, areas, and signal‐to‐noise (S/N) ratios ranging from ∞ to 5.8. As the S/N ratio decreased below 15, the M‐L algorithm located peak centers accurately when they were detected; however, small peaks tended to grow smaller and disappear, whereas the amplitudes of larger peaks increased. We developed an in vitro three‐compartment model containing a mixture of Pi buffer, phosphocreatine, phosphate diester, and phosphate monoester (PME), portions of which were adjusted to three different pHs before addition of agar. Weighed samples of each buffered gel together with phospholipid extract and bone chips were placed in an NMR tube and covered with mineral oil. Following baseline correction, it was possible to separate the Pi peaks arising from the three compartments with different pH values if each peak made up 10–35% of total Pi area. In vivo, we identified the plasma compartment by intraarterial infusion of Pi. It was assumed that intracellular compartments contained high‐energy phosphates and took up glucose. Based on these assumptions we subjected the brains to complete ischemia and observed that Pi compartments at pH 6.82, 6.92, 7.03, and 7.13 increased markedly in amplitude. If the brain cells took up and phosphorylated 2‐deoxyglucose (2‐DG), 2‐DG‐6‐phosphate (2‐DG‐6‐P) would appear in the PME portion of the spectrum ionized according to pHi. Four 2‐DG‐6‐P peaks with calculated pH values of 6.86, 6.94, 7.04, and 7.15 did appear in the spectrum, thereby confirming that the four larger Pi peaks represented intracellular spaces.