Postischemic inhibition of cerebral cortex pyruvate dehydrogenase

Distribution of neuronal populations containing neurofilament protein and calcium-binding proteins in the canine neocortex: regional analysis and cell typology

Neurophysiological experiments in carnivores have revealed the existence of a large number of cortical regions and an organization of sensory systems quite similar to that found in primates. However, the cyto- and chemoarchitecture of the cerebral cortex is relatively poorly known in carnivores. We analyzed the distribution and typology of classes of neurons containing neurofilament protein or the calcium-binding proteins parvalbumin, calbindin, and calretinin in six neocortical regions of the dog. In all these areas, neurofilament protein was present in a subpopulation of medium-to-large size pyramidal neurons predominantly distributed in layers III and V. Parvalbumin was present in a large population of morphologically diverse interneurons. Small ovoid and multipolar neurons were observed throughout the cortical layers, but predominated in layers II and IV. Layers III and V-VI were characterized by the presence of larger and intensely immunoreactive neurons with bitufted or multipolar morphology, and layers V-VI also contained large multipolar neurons. Calbindin was observed in small round and multipolar interneurons in layer II, and typical double bouquet cells in layer III. Layers IV-VI contained isolated double bouquet cells and large multipolar neurons. A few calbindin-immunoreactive pyramidal neurons were also observed in layer V. Calretinin was localized in bipolar and double bouquet cells in layers II and upper III. The lower part of layer III and layers IV-VI contained rare calretinin-immunoreactive neurons. In some areas, layer III displayed a few large isolated multipolar neurons and pyramidal neurons containing calretinin. In addition, the results show that there is a substantial degree of variability in the distribution of these proteins among cortical regions, and that although they are found in morphologically comparable neuronal types in dog, monkeys, and humans, many differences exist in their regional distribution patterns between carnivores and primates.

Distribution of neurofilament protein and calcium-binding proteins parvalbumin, calbindin, and calretinin in the canine hippocampus

Neurofilament protein and calcium-binding proteins parvalbumin, calbindin, and calretinin are present in morphologically distinct neuronal subpopulations in the mammalian cerebral cortex. Immunohistochemical studies of the hippocampal formation and neocortex have demonstrated that while neurofilament protein and calbindin are localized in subsets of pyramidal neurons, the three calcium-binding proteins are useful markers to differentiate non-overlapping populations of interneurons. To date, most studies have been performed in rodents and primates. In the present analysis, we analyzed the distribution of these proteins in the canine hippocampus. Neurofilament protein was present in large multipolar neurons in the hilus and in pyramidal neurons in the CA3 field, whereas pyramidal neurons in the CA1 field and subiculum were less intensely immunoreactive. Parvalbumin immunoreactivity was observed in large multipolar neurons in the hilus and throughout the CA3-CA1 fields, in a few pyramidal-shaped neurons in the CA1 field and subiculum, and had a distinct neuropil staining pattern in the granule cell layer and stratum pyramidale of the Ammon's horn. Calbindin immunoreactivity displayed a strong labeling of the granule cells and mossy fibers and was also observed in a population of moderately immunoreactive neurons in the CA1 field and subiculum. Calretinin immunoreactivity was relatively weaker overall. The inner molecular layer in the dentate gyrus had a distinct band of labeling, the stratum lacunosum/moleculare contained a punctate neuropil staining, and there were a few small multipolar neurons in the hilus, CA3-CA1 fields, and subiculum. Comparison of the staining patterns observed in the dog hippocampus with those in human, macaque monkeys and rats revealed that although there are some subregional differences among these taxa, the dog may constitute a valuable large animal model for the study of certain neurological conditions that affect humans, in spite of the phylogenetic distance between carnivores and primates.

Distribution of glutamate receptor subunit proteins GluR2(4), GluR5/6/7, and NMDAR1 in the canine and primate cerebral cortex: a comparative immunohistochemical analysis

The distribution of the AMPA, kainate and NMDA glutamate receptor subunit proteins GluR2(4), GluR5/6/7 and NMDAR1, respectively, were analyzed in the dog hippocampus and neocortex and compared to macaque monkeys and humans. In the dog hippocampus, these glutamate receptor classes exhibited a comparable distribution with few differences in densities of labeled of neurons in the CA1-CA3 fields and in neuropil staining patterns in the dentate gyrus. In particular, the GluR5/6/7 subunit proteins were characterized by a more restricted cellular distribution in the CA1-CA3 fields. In the dog neocortex, the GluR2(4) subunit was found in a higher number of neurons in layers III and V compared to the GluR5/6/7 or NMDAR1 subunits, which were found predominantly in a population of medium-to-large layer V pyramidal neurons. Layers II and VI were consistently densely labeled with all three receptor classes, especially in the case of the GluR5/6/7 and NMDAR1 subunits. All three antibodies used thus far showed an intense labeling of the perikaryon and dendritic segments in the dog cerebral cortex. Apical dendrites could be followed through several layers in some cases, and formed well-stained plexuses in all of the neocortical layers. These patterns were very similar to those observed in the hippocampus and neocortex of both monkey and human, although GluR2(4) and NMDAR1 immunoreactivity was visualized in more heterogeneous populations of cortical neurons in the primates than in dogs. Glutamate is the principal excitatory neurotransmitter in the brain and is involved in the excitotoxic mechanisms occurring in pathologic conditions such as epilepsy and cerebral ischemia. The dog has been shown to represent a reliable large animal model for several neurologic disorders and is used particularly in investigations of the cerebral repercussions of cardiac arrest. The overall similarity of the staining patterns in dogs and primates observed in the present study suggest that the dog model may be highly valuable for the characterization of potential cellular and synaptic shifts in the distribution and expression of specific glutamate receptor subunits, in the context of other biochemical and morphologic effects of global brain ischemia and reperfusion following cardiac arrest.

Acetyl-L-carnitine attenuates neuronal damage in gerbils with transient forebrain ischemia only when given before the insult

The underlying mechanisms leading to neuronal damage in cerebral ischemia are multifactoral. In this study, we evaluated the neuroprotective effects of acetyl-L-carnitine, a medication that may enhance metabolic recovery after cerebral ischemia. The 5-minute transient forebrain ischemia model in gerbils was used. Acetyl-L-carnitine was given 30 minutes before the insult in one set of animals and 30 minutes after the insult in a second set of animals with histological evaluation at 7 days (Group A) and 28 days (Group B). Damage assessment was done using a 4-point damage score and Mann-Whitney U test was used for statistical analysis. Compared to the controls, there was significant protection in the cerebral cortex, hippocampus and the striatum in animals treated with the medication before the insult in Group A and Group B. Post-ischemic therapy showed little evidence of neuronal protection in either group. Behavioral tests in the Group B animals showed no significant differences between the treated or the saline controls. Our study shows, that pre-ischemic treatment with acetyl-L-carnitine results in neuronal protection. This may have clinical significance in situations (such as bypass surgery) where treatment could be initiated prior to the insult.