Subpopulation Of Nonpyramidal Neurons Research Articles

Diffuse perineuronal nets and modified pyramidal cells immunoreactive for glutamate and the GABA A receptor α1 subunit form a unique entity in rat cerebral cortex

Perineuronal nets (PNs) consisting of polyanionic chondroitin sulfate proteoglycans (CSPG) and other extracellular matrix components create an exceptional microenvironment around certain types of neurons. In rat neocortex, three types of PNs can be distinguished after staining with Wisteria floribunda agglutinin (WFA) by their different morphological structure: lattice-like PNs associated with subpopulations of nonpyramidal neurons, weakly labeled PNs showing a pyramidal morphology, and diffuse PNs that possess a thick, strongly labeled matrix sheath located mainly in layer VIb above the white matter. The type of neuron surrounded by diffuse nets has not been described so far. This study is focused on the cytochemical and morphological characteristics of neurons associated with diffusely contoured PNs in rat parietal cortex using immunocytochemical staining, intracellular injection, and retrograde tracing methods. Cells surrounded by diffuse PNs were glutamate-immunoreactive in contrast to nonpyramidal, net-associated neurons that showed immunoreactivity for GABA, the calcium-binding protein parvalbumin and the potassium channel subunit Kv3.1b. Both groups of PN-ensheathed cells were mostly immunoreactive for the GABA A receptor α1 subunit. Lucifer Yellow-injected neurons surrounded by diffuse PNs displayed the morphological properties of modified pyramidal cells with intracortical main axons. Many neurons with diffuse PNs were retrogradely labeled over a long distance after Fluoro-Gold tracer injection in the parietal cortex, but remained unlabeled after intrathalamic injection. We conclude that neurons associated with diffuse PNs are a subpopulation of glutamatergic modified pyramidal cells that could act as excitatory long-range intracortically projecting neurons.

Localization of the CB1 type cannabinoid receptor in the rat basolateral amygdala: high concentrations in a subpopulation of cholecystokinin-containing interneurons

The neuronal localization of the CB1 cannabinoid receptor in the rat basolateral amygdala was studied using peroxidase and fluorescence immunohistochemical techniques. All nuclei of the basolateral amygdala contained a large number of lightly stained pyramidal neurons and a small number of more intensely stained non-pyramidal neurons. Most of the latter cells had medium-sized to large multipolar somata and three to four aspiny dendrites, but some exhibited smaller oval somata. The axon initial segments of some of these non-pyramidal neurons exhibited large swollen varicosities in colchicine-injected animals, suggesting that much of the CB1 receptor protein is transported down the axons of these cells. Double-labeling studies using immunofluorescence histochemistry combined with confocal laser scanning microscopy revealed that the great majority of non-pyramidal neurons with CB1 receptor immunoreactivity belonged to a cholecystokinin-containing subpopulation. Whereas none of the other subpopulations of non-pyramidal neurons (exhibiting immunoreactivity for calretinin, parvalbumin, or somatostatin) expressed high levels of CB1 receptor immunoreactivity, a small percentage of these cells exhibited low levels of immunoreactivity. The results indicate that cannabinoids may modulate the activity of pyramidal projection neurons as well as a subpopulation of cholecystokinin-containing non-pyramidal neurons in the basolateral amygdala. Previous studies indicate that most of the latter are inhibitory interneurons that utilize GABA as a neurotransmitter. The intense staining of the cholecystokinin-containing interneurons and the evidence that large amounts of CB1 receptor protein are transported down the axons of these cells suggests that, as in the hippocampus, cannabinoids may inhibit the release of GABA from the axon terminals of these neurons.

Colocalization of calcium-binding proteins and GABA in neurons of the rat basolateral amygdala

The basolateral amygdala contains subpopulations of non-pyramidal neurons that express the calcium-binding proteins parvalbumin, calbindin-D28k (calbindin) or calretinin. Although little is known about the exact functions of these proteins, they have provided useful markers of specific neuronal subpopulations in studies of the neuronal circuitry of the cerebral cortex and other brain regions. The purpose of the present study was to investigate whether basolateral amygdalar non-pyramidal neurons containing parvalbumin, calbindin, or calretinin exhibit immunoreactivity for GABA, and to determine if calretinin is colocalized with parvalbumin or calbindin in the rat basolateral amygdala. Pyramidal neurons were distinguished from non-pyramidal neurons on the basis of staining intensity. Using immunofluorescence confocal laser scanning microscopy, as well as the ‘mirror technique’ on immunoperoxidase-stained sections, it was found that there was virtually no colocalization of calretinin with parvalbumin or calbindin, but that the great majority of basolateral amygdalar non-pyramidal neurons containing parvalbumin, calbindin, or calretinin exhibited GABA immunoreactivity. Calbindin-positive neurons constituted almost 60% of the GABA-containing population in both subdivisions of the basolateral nucleus and more than 40% of the GABA-containing population in the lateral nucleus. Parvalbumin-positive neurons constituted 19–43% of GABA-immunoreactive neurons in the basolateral amygdala, depending on the nucleus. Calretinin-positive non-pyramidal neurons constituted about 20% of the GABA-positive neuronal population in each nucleus of the basolateral amygdala. These findings indicate that non-pyramidal neurons containing parvalbumin, calbindin, or calretinin comprise the majority of GABA-containing neurons in the basolateral amygdala, and that the calretinin subpopulation is distinct from non-pyramidal subpopulations containing parvalbumin and calbindin. These separate neuronal populations may play unique roles in the inhibitory circuitry of the amygdala.

Phospholipid metabolism activated by the stimulation of glutamate receptors in HEK 293 cells stably expressing glutamate receptors- 31P-NMR study-

The basolateral amygdala contains subpopulations of non-pyramidal neurons that express the calcium-binding proteins parvalbumin, calbindin-D28k (calbindin) or calretinin. Although little is known about the exact functions of these proteins, they have provided useful markers of specific neuronal subpopulations in studies of the neuronal circuitry of the cerebral cortex and other brain regions. The purpose of the present study was to investigate whether basolateral amygdalar non-pyramidal neurons containing parvalbumin, calbindin, or calretinin exhibit immunoreactivity for GABA, and to determine if calretinin is colocalized with parvalbumin or calbindin in the rat basolateral amygdala. Pyramidal neurons were distinguished from non-pyramidal neurons on the basis of staining intensity. Using immunofluorescence confocal laser scanning microscopy, as well as the ‘mirror technique’ on immunoperoxidase-stained sections, it was found that there was virtually no colocalization of calretinin with parvalbumin or calbindin, but that the great majority of basolateral amygdalar non-pyramidal neurons containing parvalbumin, calbindin, or calretinin exhibited GABA immunoreactivity. Calbindin-positive neurons constituted almost 60% of the GABA-containing population in both subdivisions of the basolateral nucleus and more than 40% of the GABA-containing population in the lateral nucleus. Parvalbumin-positive neurons constituted 19–43% of GABA-immunoreactive neurons in the basolateral amygdala, depending on the nucleus. Calretinin-positive non-pyramidal neurons constituted about 20% of the GABA-positive neuronal population in each nucleus of the basolateral amygdala.These findings indicate that non-pyramidal neurons containing parvalbumin, calbindin, or calretinin comprise the majority of GABA-containing neurons in the basolateral amygdala, and that the calretinin subpopulation is distinct from non-pyramidal subpopulations containing parvalbumin and calbindin. These separate neuronal populations may play unique roles in the inhibitory circuitry of the amygdala.

Calbindin-D28k immunoreactivity in the rat amygdala

Calbindin-D28k (CB) is a calcium-binding protein whose exact function has yet to be elucidated. Because CB is contained in distinct cell types in the nervous system, it is a valuable marker for distinguishing specific nuclear subdivisions and neuronal populations. In the present study, immunohistochemical methods were used to localize CB in the rat amygdala. A subpopulation of nonpyramidal neurons in all nuclei of the basolateral amygdala (ABL) exhibited intense CB immunoreactivity (CB-ir). CB-positive puncta resembling axon terminals were observed surrounding pyramidal perikarya in the ABL. Pyramidal neurons in caudal and lateral portions of the ABL exhibited moderate CB-ir. Intensely stained nonpyramidal neurons resembling those of the ABL were also seen in the cortical nuclei, periamygdaloid cortex, and nucleus of the lateral olfactory tract; these nuclei also contained variable numbers of moderately stained pyramidal cells. Numerous CB-positive neurons were observed in all subdivisions of the medial nucleus. The posterodorsal subdivision of the medial nucleus exhibited a centrally located island of small CB-negative neurons and three cell-dense clusters of CB-positive neurons. The distribution of CB-ir in the central nuclear complex was very heterogeneous. The intermediate subdivision of the central nuclear complex exhibited the most robust staining, whereas the lateral subdivision contained relatively few CB-positive cells. Dorsal and ventral portions of the lateral capsular subdivision of the central nuclear complex could be readily distinguished on the basis of differing levels of CB-ir. These results indicate that CB is localized in discrete cell types and nuclear subdivisions in the rat amygdala and suggest that CB immunohistochemistry is a useful technique for identifying specific structural components in this brain region.

Pyramidal cells ensheathed by perineuronal nets in human motor and somatosensory cortex.

This study presents data concerning the distribution of chondroitin sulphate proteoglycan-immunoreactive perineuronal nets in sensorimotor areas (Brodmann's areas 3, 1, 2 and 4) of the human cerebral cortex. In addition to previously described subpopulations of nonpyramidal neurons in neocortical areas, many large or medium-sized pyramidal cells in layers III and V, including Betz cells in the motor cortex, were shown to be net-associated and constitute about one-third of all net-associated cells. Such widespread occurrence of perineuronal nets around subpopulations of pyramidal cells is known from macaque monkeys but not from the cortex of myomorph rodents. Thus it appears that a certain proportion of net-associated pyramidal cells distinguishes individual cortical areas in highly evolved primates. This ratio may vary also with respect to species-dependent organization principles in nonprimate mammals.

Localization of AMPA glutamate receptor subunits in subpopulations of non-pyramidal neurons in the rat basolateral amygdala

A two-color immunoperoxidase technique was used to investigate the localization of GluR1 and GluR2/3 α-amino 3-hydroxy-5-methyl-4-isoxazole (AMPA) glutamate receptor subunits in subpopulations of non-pyramidal neurons in the rat basolateral amygdala. Antibodies to neuropeptide Y (NPY), vasoactive intestinal peptide (VIP), and calcium binding proteins were used to mark three distinct subsets of non-pyramidal cells. Only non-pyramidal neurons containing the calcium binding proteins parvalbumin (PV) and calbindin D-28k (CB) exhibited robust GluR1-like immunoreactivity (GluR1-ir). Light GluR1-ir was observed in some neurons with NPY-ir and VIP-ir, as well as in some pyramidal cells. Only pyramidal cells exhibited robust GluR2/3-ir. No significant amount of GluR2/3-ir was seen in any of the three main classes of non-pyramidal cells. These findings indicate that in the rat basolateral amygdala GluR2/3-ir is found primarily in pyramidal neurons whereas GluR1-ir is found mainly in non-pyramidal neurons that contain PV or CB.

Calretinin is present in non-pyramidal cells of the rat hippocampus—III. Their inputs from the median raphe and medial septal nuclei

The subcortical innervation of a recently described subpopulation of non-pyramidal neurons, containing the calcium binding protein, calretinin, was investigated in the rat hippocampus using the anterograde tracer Phaseolus vulgaris-leucoagglutinin and double immunocytochemistry for calretinin and serotonin at the light and electron microscopic levels. Our results show that the GABAergic component of the septohippocampal pathway and the serotonergic raphe afferents establish multiple synaptic contacts with the calretinin-immunoreactive interneurons. The majority of the targets of both pathways were spine-free calretinin neurons known to innervate the dendritic region of the principal cells, but the GABAergic septal pathway was found to terminate also on the spiny neurons of stratum lucidum of the CA3 region and in the dentate hilus. The present results demonstrate that the serotonergic raphe-hippocampal and the GABAergic septo-hippocampal pathways are able to modulate dendritic inhibition of principal cells via calretinin-containing GABAergic interneurons.