This study aimed at determining the distribution and expression levels of different subtypes of C... more This study aimed at determining the distribution and expression levels of different subtypes of Ca(2+) channels in the bovine adrenal medulla, and whether individual subtypes were more abundant in chromaffin cells exhibiting an adrenergic or a noradrenergic phenotype. In situ hybridization using riboprobes specific for the pore-forming Ca(2+) channel alpha(1D) (L-type channel), alpha(1B) (N-type channel), and alpha(1A) (P/Q-type channel) subunits of bovine chromaffin cells showed a broad distribution of the three transcripts in adrenal medulla tissue. However, a tissue-specific expression pattern of individual subunits was found; whereas alpha(1B) mRNA was homogeneously distributed throughout the medulla, alpha(1D) and alpha(1A) transcripts were present at higher densities in the internal medullary area, far away from the adrenal cortex. These results were corroborated by comparative analysis of the alpha(1B), alpha(1D), and alpha(1A) products amplified by RT-PCR from total RNA extracted from small pieces of tissue dissected out from external or internal medullary areas. Interestingly, immunohistochemical experiments performed in adrenal gland sections, using antidopamine-beta-hydroxylase and anti-phenylethanolamine-N-methyltransferase antibodies, indicated a higher density of noradrenergic over adrenergic chromaffin cells in the internal medullary region. These results provide direct evidence in favor of a heterogeneous distribution of Ca(2+) channel subtypes in the adrenal medulla, in agreement with previous functional data showing that blockade of the high K+ -elicited responses by dihydropyridines was greater in noradrenergic than in adrenergic chromaffin cells. These differences may be relevant for the differential release regulation of each catecholamine under physiological and pathophysiological conditions.
Transient focal cerebral ischemia leads to extensive excitotoxic glial damage in the subcortical ... more Transient focal cerebral ischemia leads to extensive excitotoxic glial damage in the subcortical white matter. Efficient reuptake of released glutamate is essential for preventing glutamate receptor overstimulation and neuronal and glial death. The present study evaluates the expression of the main glutamate transporters (EAAT1, EAAT2, and EAAT3) in subcortical white matter of the rat after transient middle cerebral artery occlusion. Western blot analysis and immunohistochemistry show an increase in the expression of EAAT1 and EAAT2 in subcortical white matter early after ischemia which subsequently decreases at longer reperfusion periods. However, expression of both EAAT1 and EAAT2 remains higher in astrocytes forming the gliotic scar and in microglial/macrophage cells at the border of or within the infarct area, respectively. Taken together, these results indicate that there is a transient enhanced expression of EAATs in the subcortical white matter early after ischemia. Our findings reveal an adaptive response of subcortical white matter to increased levels of glutamate during focal cerebral ischemia which may limit excitotoxic damage.
This study aimed at determining the distribution and expression levels of different subtypes of C... more This study aimed at determining the distribution and expression levels of different subtypes of Ca(2+) channels in the bovine adrenal medulla, and whether individual subtypes were more abundant in chromaffin cells exhibiting an adrenergic or a noradrenergic phenotype. In situ hybridization using riboprobes specific for the pore-forming Ca(2+) channel alpha(1D) (L-type channel), alpha(1B) (N-type channel), and alpha(1A) (P/Q-type channel) subunits of bovine chromaffin cells showed a broad distribution of the three transcripts in adrenal medulla tissue. However, a tissue-specific expression pattern of individual subunits was found; whereas alpha(1B) mRNA was homogeneously distributed throughout the medulla, alpha(1D) and alpha(1A) transcripts were present at higher densities in the internal medullary area, far away from the adrenal cortex. These results were corroborated by comparative analysis of the alpha(1B), alpha(1D), and alpha(1A) products amplified by RT-PCR from total RNA extracted from small pieces of tissue dissected out from external or internal medullary areas. Interestingly, immunohistochemical experiments performed in adrenal gland sections, using antidopamine-beta-hydroxylase and anti-phenylethanolamine-N-methyltransferase antibodies, indicated a higher density of noradrenergic over adrenergic chromaffin cells in the internal medullary region. These results provide direct evidence in favor of a heterogeneous distribution of Ca(2+) channel subtypes in the adrenal medulla, in agreement with previous functional data showing that blockade of the high K+ -elicited responses by dihydropyridines was greater in noradrenergic than in adrenergic chromaffin cells. These differences may be relevant for the differential release regulation of each catecholamine under physiological and pathophysiological conditions.
Transient focal cerebral ischemia leads to extensive excitotoxic glial damage in the subcortical ... more Transient focal cerebral ischemia leads to extensive excitotoxic glial damage in the subcortical white matter. Efficient reuptake of released glutamate is essential for preventing glutamate receptor overstimulation and neuronal and glial death. The present study evaluates the expression of the main glutamate transporters (EAAT1, EAAT2, and EAAT3) in subcortical white matter of the rat after transient middle cerebral artery occlusion. Western blot analysis and immunohistochemistry show an increase in the expression of EAAT1 and EAAT2 in subcortical white matter early after ischemia which subsequently decreases at longer reperfusion periods. However, expression of both EAAT1 and EAAT2 remains higher in astrocytes forming the gliotic scar and in microglial/macrophage cells at the border of or within the infarct area, respectively. Taken together, these results indicate that there is a transient enhanced expression of EAATs in the subcortical white matter early after ischemia. Our findings reveal an adaptive response of subcortical white matter to increased levels of glutamate during focal cerebral ischemia which may limit excitotoxic damage.
This study aimed at determining the distribution and expression levels of different subtypes of C... more This study aimed at determining the distribution and expression levels of different subtypes of Ca(2+) channels in the bovine adrenal medulla, and whether individual subtypes were more abundant in chromaffin cells exhibiting an adrenergic or a noradrenergic phenotype. In situ hybridization using riboprobes specific for the pore-forming Ca(2+) channel alpha(1D) (L-type channel), alpha(1B) (N-type channel), and alpha(1A) (P/Q-type channel) subunits of bovine chromaffin cells showed a broad distribution of the three transcripts in adrenal medulla tissue. However, a tissue-specific expression pattern of individual subunits was found; whereas alpha(1B) mRNA was homogeneously distributed throughout the medulla, alpha(1D) and alpha(1A) transcripts were present at higher densities in the internal medullary area, far away from the adrenal cortex. These results were corroborated by comparative analysis of the alpha(1B), alpha(1D), and alpha(1A) products amplified by RT-PCR from total RNA extracted from small pieces of tissue dissected out from external or internal medullary areas. Interestingly, immunohistochemical experiments performed in adrenal gland sections, using antidopamine-beta-hydroxylase and anti-phenylethanolamine-N-methyltransferase antibodies, indicated a higher density of noradrenergic over adrenergic chromaffin cells in the internal medullary region. These results provide direct evidence in favor of a heterogeneous distribution of Ca(2+) channel subtypes in the adrenal medulla, in agreement with previous functional data showing that blockade of the high K+ -elicited responses by dihydropyridines was greater in noradrenergic than in adrenergic chromaffin cells. These differences may be relevant for the differential release regulation of each catecholamine under physiological and pathophysiological conditions.
Transient focal cerebral ischemia leads to extensive excitotoxic glial damage in the subcortical ... more Transient focal cerebral ischemia leads to extensive excitotoxic glial damage in the subcortical white matter. Efficient reuptake of released glutamate is essential for preventing glutamate receptor overstimulation and neuronal and glial death. The present study evaluates the expression of the main glutamate transporters (EAAT1, EAAT2, and EAAT3) in subcortical white matter of the rat after transient middle cerebral artery occlusion. Western blot analysis and immunohistochemistry show an increase in the expression of EAAT1 and EAAT2 in subcortical white matter early after ischemia which subsequently decreases at longer reperfusion periods. However, expression of both EAAT1 and EAAT2 remains higher in astrocytes forming the gliotic scar and in microglial/macrophage cells at the border of or within the infarct area, respectively. Taken together, these results indicate that there is a transient enhanced expression of EAATs in the subcortical white matter early after ischemia. Our findings reveal an adaptive response of subcortical white matter to increased levels of glutamate during focal cerebral ischemia which may limit excitotoxic damage.
This study aimed at determining the distribution and expression levels of different subtypes of C... more This study aimed at determining the distribution and expression levels of different subtypes of Ca(2+) channels in the bovine adrenal medulla, and whether individual subtypes were more abundant in chromaffin cells exhibiting an adrenergic or a noradrenergic phenotype. In situ hybridization using riboprobes specific for the pore-forming Ca(2+) channel alpha(1D) (L-type channel), alpha(1B) (N-type channel), and alpha(1A) (P/Q-type channel) subunits of bovine chromaffin cells showed a broad distribution of the three transcripts in adrenal medulla tissue. However, a tissue-specific expression pattern of individual subunits was found; whereas alpha(1B) mRNA was homogeneously distributed throughout the medulla, alpha(1D) and alpha(1A) transcripts were present at higher densities in the internal medullary area, far away from the adrenal cortex. These results were corroborated by comparative analysis of the alpha(1B), alpha(1D), and alpha(1A) products amplified by RT-PCR from total RNA extracted from small pieces of tissue dissected out from external or internal medullary areas. Interestingly, immunohistochemical experiments performed in adrenal gland sections, using antidopamine-beta-hydroxylase and anti-phenylethanolamine-N-methyltransferase antibodies, indicated a higher density of noradrenergic over adrenergic chromaffin cells in the internal medullary region. These results provide direct evidence in favor of a heterogeneous distribution of Ca(2+) channel subtypes in the adrenal medulla, in agreement with previous functional data showing that blockade of the high K+ -elicited responses by dihydropyridines was greater in noradrenergic than in adrenergic chromaffin cells. These differences may be relevant for the differential release regulation of each catecholamine under physiological and pathophysiological conditions.
Transient focal cerebral ischemia leads to extensive excitotoxic glial damage in the subcortical ... more Transient focal cerebral ischemia leads to extensive excitotoxic glial damage in the subcortical white matter. Efficient reuptake of released glutamate is essential for preventing glutamate receptor overstimulation and neuronal and glial death. The present study evaluates the expression of the main glutamate transporters (EAAT1, EAAT2, and EAAT3) in subcortical white matter of the rat after transient middle cerebral artery occlusion. Western blot analysis and immunohistochemistry show an increase in the expression of EAAT1 and EAAT2 in subcortical white matter early after ischemia which subsequently decreases at longer reperfusion periods. However, expression of both EAAT1 and EAAT2 remains higher in astrocytes forming the gliotic scar and in microglial/macrophage cells at the border of or within the infarct area, respectively. Taken together, these results indicate that there is a transient enhanced expression of EAATs in the subcortical white matter early after ischemia. Our findings reveal an adaptive response of subcortical white matter to increased levels of glutamate during focal cerebral ischemia which may limit excitotoxic damage.
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