Cerebral ischemia: changes in monoamines are independent of energy metabolism.

The relationship of neurotransmitters and neuroeffectors to the energy state of the brain was examined in the gerbil model of ischemia after 5 and 15 min of bilateral common carotid artery occlusion only or with 1 hr of reperfusion. The gerbil brains were fixed by microwave irradiation and a total of 15 metabolites were measured from a single piece of tissue from either the hippocampus or the striatum. The rapid alterations in energy-related compounds and cyclic nucleotides appeared to be directly related both to the loss of oxygen and glucose during ischemia and the resupply of these nutrients during reflow. Significant reduction in the level of monoamines occurred principally during reflow, at a time when the energy-related metabolites were restored. It is proposed that the changes in monoamines were triggered by other ischemic-induced events unrelated to energy depletion.

Glutathione reductase during and after brain ischemia in gerbils.

The activity of glutathione reductase (GR) was measured in crude mitochondrial fraction isolated from cerebral cortex and basal ganglia of Mongolian gerbils subjected to bilateral carotid occlusion of various duration (1, 2, 3, 5, 10, and 15 min), or reflow (1, 24, and 96 hr) following ischemia (5 or 15 min). Ischemia up to 5 min does not induce changes in GR activity in either structure. Basal ganglia activity is halved at 10 min and cortical at 15 min of ischemia. In reflow, basal ganglia GR activity is diminished, while cortical GR is transiently reduced at day 1 of reflow. The persistent and profound decrease in GR activity in basal ganglia following ischemia is indicative of the lowered antioxidative capacity of these cells, being possibly related to their greater vulnerability toward ischemia.

Depression and Parkinson's disease: possible role of serotonergic mechanisms.

Depression is frequently encountered in Parkinson's disease and was seen to occur in 14 of 26 patients studied. The levels of 5-hydroxyindoleacetic acid (5-HIAA), the main metabolite of serotonin (5-HT), in CSF samples of the patients were significantly lower than in those of controls. However, within the group of patients the levels of 5-HIAA in CSF samples were significantly lower in the depressive subgroup compared with the non-depressive patients. Moreover, no correlation was recorded between motor disability and depression. The results indicate that disturbed 5-HT metabolism may possibly play a role in Parkinson's disease as a predisposing factor in the development of depression.

Cyclic nucleotides in cerebrospinal fluid of drug-free Parkinson patients.

Concentrations of cyclic nucleotides--adenosine-3',5'-monophosphate (c-AMP) and guanosine-3',5'-monophosphate (c-GMP)--were measured in cerebrospinal fluid (CSF) of 17 drug-free Parkinson patients and 12 controls. No significant difference between the cyclic nucleotide contents (p greater than 0.05) in CSF of patients and controls was detected, nor was there a correlation between the content and the degree of neurological disability. Besides, no changes in the cyclic nucleotide contents were detected in the subgroups of patients according to the prominence of tremor or rigidity/akinesia as the main symptoms of the disease.

Measurement of solute transport across the blood-brain barrier in the perfused guinea pig brain: method and application to N-methyl-alpha-aminoisobutyric acid.

A technique for the vascular perfusion of the guinea pig head in vivo, suitable for measurements of blood-to-brain transport under controlled conditions of arterial inflow, has been developed. With a perfusion pressure ranging between 13 and 18 kPa and PCO2 in the arterial inflow of 5 and 5.5 kPa, cerebral blood flow, measured with [14C]butanol, was about 1 ml min-1 g-1 in the cerebral cortex, hippocampus, and caudate-putamen of the ipsilateral hemisphere; in the cerebellum and pontine white matter it was considerably less, and much higher perfusion pressures were required to establish equal blood flow throughout the whole brain. Regional water content, Na+/K+ ratio, ATP, energy charge potential, and lactate content of the ipsilateral side of perfused and nonperfused brain were not significantly different after 10 min perfusion. The D-[3H]mannitol space did not exceed 1% after 30 min of perfusion, indicating the integrity of the barrier. Over this period, EEG, ECG, and respiratory waveform remained normal. When [14C]N-methyl-alpha-aminoisobutyric acid (MeAIB), and D-[3H]mannitol were perfused together over periods extending to 30 min progressive uptakes of both solutes by the parietal cortex could be measured, and the unidirectional transfer constants estimated from multiple time-uptake data. The Kin for MeAIB (0.75 X 10(-3) ml min-1 g-1) was some three times that for mannitol. It is concluded that the technique provides a stable, well-controlled environment in the cerebral microvasculature of the ipsilateral perfused brain hemisphere suitable for examining the transport of slowly penetrating solutes into the brain.

Composite technique for regional neurochemical studies: measurement of energy and neurotransmitter metabolites in single tissue sample.

A combined method is described for the determination of various metabolites from a single tissue sample of the brain. It comprises a quick inactivation of cerebral enzymes by microwave irradiation, easy separation of the desired brain regions, and perchloric acid extraction of tissue substances, which are assayed either by specific enzymatic techniques or by HPLC with electrochemical detection. The obtained values of most energy and neurotransmitter metabolites in the brain are in agreement with those reported using other methods. However, this technique, in contrast to the brain freezing in vitro or freeze-blowing, provides a more efficient procedure for rapid arrest of cerebral metabolism even in the deep brain structures and is therefore suitable for detection of early changes particularly those occurring in experimental pathological conditions such as ischemia.

Cyclic AMP in the cerebrospinal fluid of patients with recent cerebral infarction.

The concentrations of cyclic adenosine 3',5'-monophosphate (c-AMP) and glucose were measured in cerebrospinal fluid (CSF) of 43 patients with recent cerebral infarction divided into five groups in respect to the time (up to 24 h) elapsed between cerebrovascular insult and CSF sampling. 10 of the additionally studied subjects were (control group) neurologically normal. None of the investigated subjects was under therapy at the time of CSF sampling. The levels of c-AMP and glucose in patients with cerebral infarction were found not to be related to the degree of neurological deficit but to the duration of ischemia. CSF c-AMP was elevated (p less than 0.001) for 8-12 h following the cerebrovascular insult and subsequently reached the level of controls. The CSF glucose level was elevated during the whole period of observation.

Cerebrospinal fluid prostaglandin F2 alpha in stroke patients: no relationship to the degree of neurological deficit.

The concentration of prostaglandin F2 alpha (PGF2 alpha) was measured in cerebrospinal fluid (CSF) of 50 patients with recent stroke divided into three groups in respect to the time (up to 24 h) that expired between cerebrovascular insult and CSF sampling. 10 of the additionally studied persons were neurologically normal (control group). None of the investigated subjects were undergoing any therapy at the time of CSF sampling. The estimation of the neurological score revealed that the stroke patients suffered from acute cerebral ischemic attacks of varying severity. No relationship between the CSF PGF2 alpha and neurological status was found. Within the first 4 h after the stroke a marked increase in PGF2 alpha was found, afterwards being diminished but still enhanced in comparison to the controls.

Insulin increases entrance of 2-deoxy-D-[3H]glucose in isolated rat brain microvessels.

Insulin in a dose of 0.5 U ml-1 in the incubation medium did not change ATP and phosphocreatine contents in the isolated rat brain microvessels, when energy production was supported by 5.5 mmol l-1 glucose. However, the entrance of non-metabolizable glucose analogue, 2-deoxy-D-[3H]glucose into the microvessel cells was strongly enhanced, almost 18-fold.

Biochemical changes during graded brain ischemia in gerbils. Part 1. Global biochemical alterations.

In Mongolian gerbils (Meriones unguiculatus) cerebral ischemia was produced by occlusion of the right common and the left external carotid arteries. Gerbils were classified according to their neurological appearance as "symptom-negative" (8 animals), "mild symptoms" (unilateral hemiparesis, 10 animals) and "severe symptoms" (hemiparesis and rolling seizures, 8 animals). Two hours after vascular occlusion various substrates and enzymes related to the energy-producing metabolism, were assessed in tissue samples from both hemispheres. In symptom-negative animals, the only change was a slight decrease of glycolytic intermediates in the right hemisphere. In animals with mild symptoms, the right hemisphere additionally exhibited an impairment of the redox and energy state and an enhancement of the activity of most enzymes of the glycolytic pathway, except hexokinase. In animals with severe symptoms, these changes were even more pronounced and affected--to a lesser degree--also the left hemisphere. The results obtained demonstrate that the neurological appearance of the animals after vascular occlusion correlates with the biochemical alterations and, therefore, can be used for estimating the density of graded ischemia.

Biochemical changes during graded brain ischemia in gerbils. Part 2. Regional evaluation of cerebral blood flow and brain metabolites.

Regional changes of cerebral blood flow and biochemical substrates were assessed in the gerbil brain following different grades of cerebral ischemia. Ischemia was produced by occlusion of the right common carotid and left external carotid arteries. Gerbils were classified according to the severity of neurological symptoms as animals without, with mild and with severe neurological deficits. Brains were frozen in situ, sliced in 20-microns sections and processed for pictorial presentation of glucose and ATP, using bioluminescence techniques. Cerebral blood flow was determined in adjacent brain sections, using [14C]iodoantipyrine autoradiography. NADH fluorescence was recorded by illuminating the surface of the tissue block with ultraviolet light. Most animals without visible neurological symptoms exhibited reduced blood flow in circumscribed regions of cortex and basal ganglia of the right hemisphere without concomitant changes of biochemical substrates. In animals with mild neurological symptoms, blood flow in the right hemisphere was reduced, glucose and ATP decreased, and NADH fluorescence unhomogeneously enhanced. In animals with severe neurological symptoms blood flow was almost arrested in the right hemisphere and was distinctly reduced in the medial parts of the left hemisphere. The ischemic tissue was depleted from glucose and ATP, and exhibited bright NADH fluorescence. The severity of neurological symptoms, in consequence, correlated closely with both the degree and the size of biochemical lesions observed in the ischemic territory.

The effect of physostigmine on (Na+ + K+)-ATPase activity in different rat brain regions.

The activity of (Na+ + K+)-ATPase and acetylcholine esterase were followed in rat brain cerebral cortex, caudate, thalamus, hippocampus and medulla after i.v. administration of physostigmine. Both enzymes were found to be inhibited in a dose-dependent manner. The most pronounced inhibition of (Na+ + K+)-ATPase was found in caudate, where the highest activity of acetylcholine esterase is found.

Key enzymes of glycolysis in rat brain: effects of single and repetitive treatment with dihydroergotoxine (Redergin).

The activities of hexokinase, phosphofructokinase and lactate dehydrogenase were measured in the brain of Lewis rats that were 75 days, 6 months and 12 months old. During this period (75--360 days) the activity of hexokinase declines about 5-fold, that of lactate dehydrogenase increases 2-fold, while phosphofructokinase activity is unchanged. Dihydroergotoxine treatment (25 days, 1 mg/kg body weight daily) counteracts these changes. It is concluded that repeated treatment with dihydroergotoxine increases capacity of glycolytic pathway and decreases the capacity of pyruvate to lactate conversion, which could be otherwise excessive in senescent brains under certain pathological conditions.

Brain capillary guanosine triphosphatase: a distinction from adenosine triphosphatase.

Differences in kinetic properties, pH response, sensitivity to ouabain, and disc-acrylamide electrophoresis resolution, are observed when GTP and ATP are used as the substrates for triphosphohydrolases in isolated rat brain microvessels. In brain parenchyma there are no such differences. It is concluded that substrate-specific GTPase exists in brain microvessels.

Monoamines and related enzymes in cerebral cortex and basal ganglia following transient ischemia in gerbils.

The post-ischemic effects on cerebral cortex and basal ganglia monoamine levels and monoamine oxidase (MAO A and B) and catechol-O-methyl transferase (COMT) activities were evaluated in Mongolian gerbils (Meriones unguiculatus) subjected to bilateral common carotid arteries of occlusion for 15 min and reflow for 7 days. Disorders of monoamine metabolism was found in ischemic brain which persisted during the long-term post-ischemia. A rebound increase of norepinephrine and serotonin appeared in early stages (up to 1 h) of post-ischemia both in cerebral cortex and basal ganglia; a rebound increase of dopamine as found only in cerebral cortex. Thereafter, the serotonin level ws enhanced over the control level during the whole post-ischemic period whereas the levels of catecholamines were reduced particularly in basal ganglia. With respect to monoamine content and activities of monoamine degraded enzymes an oscillatory behavior was observed in the post-ischemia. Disorder of the monoamine metabolism found during post-ischemic period possibly contributes to neurological dysfunction after an ischemic insult.

Brain microvessel hexokinase: kinetic properties.

Kinetic differences between brain capillary and parenchymal hexokinase in the presence of glucose, ATP. fructose, potassium, sodium and different pH were established. Parenchymal hexokinase is more susceptible to glucose inhibition, can tolerate greater variations in the ATP concentration, is inhibited by increasing concentrations of fructose and potassium, and showed greater activity on the lower pH values. The data suggest that in brain parenchyma and endothelial cells of brain microvessels, there are 2 different enzymes with regard to the kinetics properties.