Pascale Halleux

Homolateral cerebrocortical increase of immediate early gene and neurotransmitter messenger RNAs after minimal cortical lesion: Blockade by N- methyl-D-aspartate antagonist

A small surgical lesion of the parietal cortex induces an increase in the expression of several messenger RNAs varying from 172 to 980% in the entire homolateral cerebral cortex, as detected by quantitative in situ hybridization histochemistry. The messenger RNAs encoding the immediate early genes of the leucine zipper family (c-fos, c-jun, jun-B), the Zinc finger family (zif268), the glucocorticoid receptor family (NGFI-B) and the interferon family (PC4) are increased within 2 h after the lesion and return to normal levels at 6 h. The messenger RNAs encoding cholecystokinin, neuropeptide Y, somatostatin and the synthetizing enzyme of the neurotransmitter GABA, glutamate decarboxylase, are elevated within one day and return to normal levels after six days. An intraperitoneal injection of the N-methyl-D-aspartate receptor antagonist dizocilpine maleate, 30 min before surgery, prevented either the induction of immediate early gene expression or the increase of neuropeptide and glutamate decarboxylase messenger RNA expression. This study demonstrates that a minimal cortical lesion induces extensive changes in gene expression and that the mechanism(s) leading to these changes involves the action of glutamate at the N-methyl-D-aspartate receptor. These modifications may be of importance in explaining diffuse changes not related to neuronal circuitry in several conditions.

Distribution of immediate early gene zif-268, c-fos, c-jun and jun-D mRNAs in the adult cat with special references to brain region related to vision

The distribution of immediate early gene zif-268, c-fos, c-jun and jun-D mRNAs was investigated in the visual cortex, dorsal lateral geniculate nucleus and hippocampus of the adult cat brain with in situ hybridization. In area 17, zif-268, c-jun and jun-D were found predominantly in layers II-III and VI, while c-fos mRNA was abundant in layer VI. In area 18, the zif-268, c-fos and c-jun labelling pattern was identical to that of area 17, this was not true for jun-D. In area 19, only c-jun retained the lamination pattern of areas 17 and 18, while zif-268, c-fos and jun-D were homogeneously distributed. In the dorsal lateral geniculate nucleus, only c-fos and jun-D resulted in labelling. In the pyramidal layer of hippocampus, zif-268 was found in CA1-4, c-jun in CA1-3, and jun-D in CA2-4. In the dentate gyrus, c-jun was abundant, jun-D moderate and zif-268 faint. C-fos labelling was absent in the hippocampal formation.

Cholecystokinin mRNA detection in rat spinal cord motoneurons but not in dorsal root ganglia neurons.

Cholecystokinin (CCK) mRNA has been detected by in situ hybridization histochemistry using two different oligonucleotide probes in small to medium-sized neurons of layers II-III and X of Rexed and in large neurons of layer IX in the rat spinal cord at cervical, thoracic and lumbo-sacral levels. No labeled cells were detected in the dorsal root ganglia. This confirms the previously established distribution of CCK-like immunoreactivity in layers II-III and X and indicates, in addition, that motoneurons of layer IX may express true genuine CCK whilst conversely, dorsal root ganglia neurons do not.

Homolateral cerebrocortical changes in neuropeptide and receptor expression after minimal cortical infarction

A cortical infarct of 2 mm diameter was obtained in the parietal cortex after a craniotomy, disruption of the dura mater and topical application of 3 M KCl. It has been shown previously that the presence of a small cortical infarct induces an increase in immediate early gene messenger RNA expression followed by an increase in neuropeptide and glutamic acid decarboxylase messenger RNA expression. Glutamate, acting at N-methyl-D-aspartate receptors, is held responsible for these changes, since they are blocked by pretreatment with dizocilpine. In the present study, we have analysed the consequences of the dramatic changes in messenger RNA expression on the level of immediate early gene products c-fos and zif 268, and on that of neuropeptides by using immunohistochemistry. After just 1 h, an increase in c-fos- and zif 268-like immunoreactivity is observed in the entire cortical hemisphere homolateral to the infarct, and is no longer detected after 6 h. An increase in cholecystokinin octapeptide-, substance P-, neuropeptide Y- and somatostatin-like immunoreactivity is observed in the entire cortical hemisphere homolateral to the infarct after three days, and is no longer detected after 30 days. To investigate if these dramatic increases in neuropeptide immunoreactivities may have functional consequences, we studied the level of cholecystokinin receptors by autoradiographic binding using [125I]cholecystokinin-8S and in situ hybridization for the detection of cholecystokinin-b receptor messenger RNA. A decrease in cholecystokinin binding sites and cholecystokinin-b receptor messenger RNA is observed in the entire cortical hemisphere homolateral to the infarct after three days, and is no longer detected after nine days. This study shows that a topical stimulation has diffuse effects, reaching regions far from the site of the lesion, and some of them are still strongly present after nine days. The increase in neuropeptide messenger RNAs is followed by an increase in the protein products of these genes, which may modify the neurotransmission. As a corollary to this, a decrease in cholecystokinin binding sites occurs. This may have further consequences on signal transduction pathways. This decrease in cholecystokinin binding sites is associated with a decrease in the cholecystokinin-b receptor messenger RNA, and this is the first example of a decrease in messenger RNA levels in this experimental model.

Calcium binding protein calcyphosine in dog central astrocytes and ependymal cells and in peripheral neurons.

Calcyphosine is a calcium binding protein discovered in the dog thyroid in 1979. Calcyphosine mRNA and immunoreactivity were detected using Western and Northern blotting in the cerebral cortex, cerebral white matter and cerebellum. Using immunohistochemistry and in situ hybridization, both are present in ependymal cells, choroid plexus cells and several types of astrocytes of the subependymal cerebral layer, the cerebellar Bergmann layer, the retinal ganglion cell layer, the optic nerve and the posterior pituitary. Both are also present in neurons of nasal olfactory mucosa, enteric Auerbach and Meissner plexuses, orthosympathic and spinal cord ganglia as well as in endocrine cells of neural crest origin in the adrenal medulla. Calcyphosine immunoreactive astrocytes were also present mainly in hemispheric cerebral gray and white matter, hemispheric subcortical structures, brain stem and spinal cord. These results show that calcyphosine is a characteristic calcium binding protein of astrocytes and ependymal cells in the central nervous system and of neurons in the peripheral nervous system. This is of interest in view of the importance of calcium regulation in these cells, and since calcyphosine a calcium binding protein phosphorylated by cAMP dependent process, may be an intermediate between cAMP and inositol phosphate cascades.

Cholecystokinin distribution in the human striatum and related subcortical structures

The distribution of cholecystokinin immunoreactive nerve cell bodies and processes is reported in the human striatum and adjacent structures such as the claustrum, the pallidum, the bed nucleus of the stria terminalis and the substantia innominata. Cholecystokinin-positive terminals are present in the striatum where they are arranged in a patchy pattern. Cholecystokinin-positive somata are observed in the claustrum and in the bed nucleus of the stria terminalis but not in the striatum, the pallidum or the substantia innominata. Dense networks of cholecystokinin-positive woolly fibres are present in the bed nucleus of the stria terminalis and the substantia innominata. These results suggested that cholecystokinin is involved in the compartmental organization of the human striatum. This compartmentalization has functional and pathological implications. Involvement of the cholecystokinin system in some basal ganglia diseases is therefore expected. Presence of neuronal cholecystokinin in the accumbens nucleus, bed nucleus of the stria terminalis and substantia innominata also suggests that this peptide may interact at different levels in the human limbic system.

Neuronal localization in the rat brain of the messenger RNA encoding calcyphosine, a new calcium-binding protein.

The cDNA encoding calcyphosine, a new calcium-binding protein of the calmodulin superfamily which is regulated by cAMP, has been cloned in the dog thyroid (EMBO J., 8 (1989) 111-116). By in situ hybridization with synthetic oligonucleotides, we here demonstrate for the first time its neuronal localization in the rat brain. Hybridization signal was detected in all the olfactory areas; in pyramidal and non pyramidal-shaped neurons in the different layers of the cerebral cortex, especially the superficial ones; in the pyramidal cells of the different sectors of the Ammons horn and in the granule cells of the dentate gyrus of the hippocampus; in the subiculum; in the medium-sized and large neurons of the different quadrants of the caudate-putamen and accumbens and in the cerebellar Purkinje cells. Hybridization was also observed to a lesser extent in the majority of the neurons in the basal areas of the forebrain, including septum, nucleus of the diagonal band and amygdala; in the globus pallidus, entopeduncular nucleus, substantia nigra pars reticulata and compacta, ventral tegmental area; in the subthalamic nucleus; in the thalamus; in the hypothalamus; in the brainstem and in the upper cervical spinal cord. In addition to its neuronal localization, calcyphosine mRNA was also found in ependymal cells. The non-detection of positive cells in the white matter was not in favor of prominent glial localization, although it does not exclude it.

Transient neurotensin in the cat inferior olive during development.

By immunohistochemistry, a large number of neurotensin immunoreactive nerve terminals are found in the kitten inferior olive of the medulla oblongata. They are present in the dorsal lamella of the principal olive, in the ventrolateral outgrowth and in the medial part of the caudal dorsal accessory olive. They are absent in the medial accessory olive. They disappear in the adult cat. Neurotensin immunoreactivity is absent in the developing rat inferior olive. This localization in the cat suggests a neuronal origin in the mesencephalon, mainly in the red nucleus. These results confirm our recent report on a transient large neurotensinergic innervation of the human developing principal olive.