Calcium-binding Proteins Calbindin D28K, Calretinin, and Parvalbumin Immunoreactivity in the Rabbit Visual Cortex

The distribution and morphology of neurons containing three calcium-binding proteins, calbindin D28K, calretinin, and parvalbumin in the adult rabbit visual cortex were studied. The calcium-binding proteins were identified using antibody immunocytochemistry. Calbindin D28K-immunoreactive (IR) neurons were located throughout the cortical layers with the highest density in layer V. However, calbindin D28K-IR neurons were rarely encountered in layer I. Calretinin-IR neurons were mainly located in layers II and III. Considerably lower densities of calretinin-IR neurons were observed in the other layers. Parvalbumin-IR neurons were predominantly located in layers III, IV, V, and VI. In layers I and II, parvalbumin-IR neurons were only rarely seen. The majority of the calbindin D28K-IR neurons were stellate, round or oval cells with multipolar dendrites. The majority of calretinin-IR neurons were vertical fusiform cells with long processes traveling perpendicularly to the pial surface. The morphology of the majority of parvalbumin-IR neurons was similar to that of calbindin D28K: stellate, round or oval with multipolar dendrites. These results indicate that these three different calcium-binding proteins are contained in specific layers and cells in the rabbit visual cortex.     

The distribution and morphology of calbindin D28K- and calretinin-immunoreactive neurons in the visual cortex of mouse

We studied the distribution and morphology of calbindin D28K- and calretinin-immunoreactive (IR) neurons in the mouse visual cortex with immunocytochemistry. Most of the calbindin D28K-IR neurons were located in layers II/III and V, while calretinin-IR neurons were predominantly located in layers II/III. The labeled neurons showed variations in morphology. The majority of the calbindin D28K-IR neurons were stellate and round or oval cells with multipolar dendrites. The majority of calretinin-IR neurons were vertical fusiform cells with long processes traveling perpendicular to the pial surface. In the mouse visual cortex, 20.2% of calbindin D28K-IR neurons contained calretinin and 27.2% of calretinin-IR neurons contained calbindin D28K. These results indicate that the calcium-binding proteins, calbindin D28K and calretinin are distributed in specific layers and in selective cell types of the mouse visual cortex.     

Nitric oxide synthase and calcium-binding protein-containing neurons in the hamster visual cortex

The distribution and morphology of neurons containing neuronal nitric oxide synthase (NOS), and calcium-binding proteins calbindin D28K and calretinin in the hamster visual cortex were compared by immunocytochemistry. Staining for NOS, calbindin D28K and calretinin was seen both in the specific layers and in the selective cell types. The densest concentration of anti-NOS-immunoreactive (IR) neurons was found in layer VI. Most of the calbindin D28K-IR neurons were located in layers II/III and V while the calretinin-IR neurons were predominantly located in layers II/III. The labeled neurons varied in morphology. The large majority of NOS-IR neurons were round or oval cells with many dendrites coursing in all directions. The majority of the calbindin D28K-IR neurons were stellate and round or oval cells with multipolar dendrites. The majority of the calretinin-IR neurons were vertical fusiform cells with long processes traveling perpendicular to the pial surface. Our study showed that 14.7% and 27.5% of the NOS-IR cells in the hamster visual cortex contained calbindin D28K or calretinin, respectively. These results indicate that NOS, calbindin and calretinin are located in specific layers and specific cell types and the vast majority of NOS-containing neurons are limited to neurons that do not express calbindin D28K or calretinin.     

Organization of calbindin D28K-immunoreactive neurons in the dog superior colliculus

We localized calbindin D28K-immunoreactive (IR) neurons in the superior colliculus (SC) of the dog and studied the distribution and effect of enucleation on the distribution of this protein. We also compared this labeling to that of GABA. Calbindin D28K was localized with antibody immunocytochemistry. Calbindin D28K-IR neurons formed three laminar tiers in the SC, one within the lower superficial gray layer (SGL), the second within the upper intermediate gray layers (IGL), and the third within the deep gray layer (DGL). The third tier was not very distinctive when compared with the other two tiers. Calbindin D28K-IR neurons in the SC varied dramatically in morphology and size, and included round/oval, vertical fusiform, stellate, pyriform, and horizontal neurons. Neurons with varicose dendrite were also labeled in the IGL. Enucleation appeared to have no effect on the distribution of calbindin D28K-IR neurons in the contralateral SC. Two-color immunofluorescence revealed that a small percentage (11.20%) of calbindin D28K-IR neurons co-localized with GABA. The current results demonstrate that the patterned distribution of calbindin D28K-IR neurons in the intermediate and deep SC is comparable with other animals, but that the distribution of this protein in the superficial SC is strikingly different from that in previously studied animals. The results also suggest that retinal projection may not control the activity of the expression of calbindin D28K in the dog SC. These results will not only provide valuable knowledge of the basic neurochemical architecture of the dog visual system, but also provide clues for the understanding of the similarities and differences among species.     

Immunocytochemical localization of neurons containing the AMPA GluR2/3 subunit in the hamster visual cortex

AMPA glutamate receptors play a crucial role in brain functions such as synaptic plasticity and development. We have studied the chemo-architecture of the AMPA glutamate receptor subtype GluR2/3 in the hamster visual cortex by immunocytochemistry and compared it with the distribution of the calcium-binding proteins, calbindin D28K and calretinin. Anti-GluR2/3-immunoreactive (IR) neurons were predominantly located in layers II/III, V, and VI, and the majority of the labeled neurons were round or oval. However, many pyramidal cells in layer V were also labeled. Two-color immunofluorescence revealed that none of the GluR2/3-IR neurons contained calbindin D28 K or calretinin. Thus specific layers of neurons express the GluR2/3 subunit and these do not correlate with expression of calbindin D28K and calretinin.     

Distribution of AMPA glutamate receptor GluR1 subunit-immunoreactive neurons and their co-localization with calcium-binding proteins and GABA in the mouse visual cortex

The neuronal localization of alpha-amino-3-hydroxyl-5-methyl-4-isoxazole propionic acid (AMPA) glutamate receptor (GluR) subunits is vital as they play key roles in the regulation of calcium permeability. We have examined the distribution of the calcium permeable AMPA glutamate receptor subunit GluR1 in the mouse visual cortex immunocytochemically. We compared this distribution to that of the calcium-binding proteins calbindin D28K, calretinin, and parvalbumin, and of GABA. The highest density of GluR1-immunoreactive (IR) neurons was found in layers II/III. Enucleation appeared to have no effect on the distribution of GluR1-IR neurons. The labeled neurons varied in morphology; the majority were round or oval and no pyramidal cells were labeled by the antibody. Two-color immunofluorescence revealed that 26.27%, 10.65%, and 40.31% of the GluR1-IR cells also contained, respectively, calbindin D28K, calretinin, and parvalbumin. 20.74% of the GluR1-IR neurons also expressed GABA. These results indicate that many neurons that express calcium-permeable GluR1 also express calcium binding proteins. They also demonstrate that one fifth of the GluR1-IR neurons in the mouse visual cortex are GABAergic interneurons.     

Localization of calcium-binding protein parvalbumin-immunoreactive neurons in mouse and hamster visual cortex

Calcium-binding proteins are thought to play important roles in regulating intracellular calcium in the central nervous system. In the present study, we investigated the distribution and morphology of neurons containing parvalbumin in the visual cortex of mouse and hamster. The calcium-binding proteins were localized using immunocytochemistry. Parvalbumin-immunoreactive neurons were located in all layers except layer I. The highest density of parvalbumin immunoreactivity was found in layer V of both mouse and hamster. The labeled neurons varied in morphology. The majority of the parvalbumin-immunoreactive neurons both in mouse and hamster visual cortex was stellate and round, or oval with multipolar dendrites. These results indicate that the calcium-binding protein parvalbumin is contained in specific layers and in selective cell types of the mouse and hamster visual cortex. The distribution of parvalbumin in the mouse visual cortex is very similar to that of hamster.     

Effect of rabies virus infection on the expression of parvalbumin, calbindin and calretinin in mouse cerebral cortex

Some clinical features of rabies and experimental evidence from cell culture and laboratory animals suggest impairment of gabaergic neurotransmission. Several types of gabaergic neurons occur in the cerebral cortex. They can be identified by three neuronal markers: the calcium binding proteins (CaBPs) parvalbumin (PV), calbindin (CB) and calretinin (CR). Rabies virus spreads throughout the cerebral cortex; however, rabies cytopathic effects on gabaergic neurons are unknown. The expression of calcium-binding proteins (CaBPs) parvalbumin (PV), calbindin (CB) and calretinin (CR) was studied in the frontal cortex of mice. The effect of gabaergic neurons was evaluated immunohistochemically. The distribution patterns of CaBPs in normal mice and in mice infected with 'fixed' or 'street' rabies virus were compared. PV was found in multipolar neurons located in all cortical layers except layer I, and in pericellular clusters of terminal knobs surrounding the soma of pyramidal neurons. CB-immunoreactivity was distributed in two cortical bands. One was composed of round neurons enclosed by a heavily labeled neuropil; this band corresponds to supragranular layers II and III. The other was a weakly stained band of neuropil which contained scattered multipolar CB-ir neurons; this corresponds to infragranular layers V and VI. The CR-ir neurons were bipolar fusiform cells located in all layers of cortex, but concentrated in layers II and III. A feature common to samples infected with both types of viruses was a more intense immunoreactivity to PV in contrast to normal samples. The infection with 'street' virus did not cause additional changes in the expression of CaBPs. However, the infection with 'fixed' virus produced a remarkable reduction of CB-immunoreactivity demonstrated by the loss of CB-ir neurons and low neuropil stain in the frontal cortex. In addition, the size of CR-ir neurons in the cingulate cortex was decreased.     

Immunocytochemical localization of nitric oxide synthase-containing neurons in mouse and rabbit visual cortex and co-localization with calcium-binding proteins

Nitric oxide (NO) occurs in various types of cells in the central nervous system. We studied the distribution and morphology of neuronal nitric oxide synthase (NOS)-containing neurons in the visual cortex of mouse and rabbit with antibody immunocytochemistry. We also compared this labeling to that of calbindin D28K, calretinin, and parvalbumin. Staining for NOS was seen both in the specific layers and in selective cell types. The densest concentration of intense anti-NOS immunoreactive (IR) neurons was found in layer VI, while the weak anti-NOS-IR neurons were found in layer II/III in both animals. The NOS-IR neurons varied in morphology. The large majority of NOS-IR neurons were round or oval cells with many dendrites coursing in all directions. Two-color immunofluorescence revealed that only 16.7% of the NOS-IR cells were double-labeled with calbindin D28K in the mouse visual cortex, while more than half (51.7%) of the NOS-IR cells were double-labeled with calretinin and 25.0% of the NOS-IR cells were double-labeled with parvalbumin in mouse. By contrast, 92.4% of the NOS-IR neurons expressed calbindin D28K while only 2.5% of the NOS-IR neurons expressed calretinin in the rabbit visual cortex. In contrast with the mouse, none of the NOS-IR cells in the rabbit visual cortex were double-labeled with parvalbumin. The results indicate that neurons in the visual cortex of both animals express NOS in specific layers and cell types, which do not correlate with the expression of calbindin D28K, calretinin or parvalbumin between the two animals.     

Alterations in the localization of calbindin D28K-, calretinin-, and parvalbumin-immunoreactive neurons of rabbit retinal ganglion cell layer from ischemia and reperfusion

Calcium-binding proteins are thought to play important roles in calcium buffering. The present study investigated the effects of ischemia and reperfusion on calbindin D28K, calretinin, and parvalbumin immunoreactivity in the ganglion cell layer of the rabbit. Rabbits were administered ischemic damage by increasing the intraocular pressure. After 60 and 90 min of ischemia, reperfusion (7 d) was allowed to occur. The b-wave of the electroretinogram (ERG) was reduced by more than 50% and almost 80% in retina given ischemia for 60 and 90 min, respectively. The oscillatory potential (OPs) wave was reduced approximately 50% at 60 min ischemia and 70% at 90 min ischemia. In both normal and ischemic-treated retina, calcium-binding protein immunoreactivity was seen in many cells in the ganglion cell layer. In eyes subjected to 60 min ischemia, there was a decrease of the density of calbindin D28K- (8.29%), calretinin- (14.44%), and parvalbumin- (26.83%) immunoreactive (IR) cells compared to the control retina. In eyes subjected to 90 min ischemia, there was a higher decrease of the density of calbindin D28K- (18.48%), calretinin- (33.59%), and parvalbumin- (54.26%) IR cells than at 60 min. Some calcium-binding protein-IR neurons, especially calretinin-IR neurons, showed aggregations that were abnormally packed together in retina subjected to ischemia for 90 min. The results show that calbindin D28K-, calretinin-, and parvalbumin-IR cells in the ganglion cell layer are susceptible to ischemic damage and reperfusion. The degree of reduction varied among different calcium-binding proteins and ischemic damage times. These results suggest that calbindin D28K-containing neurons are less susceptible to ischemic damage than calretinin- and parvalbumin-containing neurons in the ganglion cell layer of rabbit retina.     

Effect of retinal ablation on the expression of calbindin D28k and GABA in the chick optic tectum

The effect of retinal ablation on qualitative and quantitative changes of calbindin D28k and GABA expression in the contralateral optic tectum was studied in young chicks. Fifteen days old chicks had unilateral retinal ablation and after 7 or 15 days, calbindin expression was analyzed by Western blot and immunocytochemistry. Neuronal degeneration was followed by the amino-cupric silver technique. After 15 days, retinal lesions produced a significant decrease in calbindin immunostaining in the neuropil of layers 5-6 and in the somata of neurons from the layers 8 and 10 of the contralateral tectum, being this effect less marked at 7 days post-lesion. Double staining revealed that 50-60% of cells in the layers 8 and 10 were calbindin and GABA positive, 30-45% were only calbindin positive and 5-10% were only GABAergic neurons. Retinal ablation also produced a decrease in the GABA expression at either 7 or 15 days after surgery. At 7 days, dense silver staining was observed in the layers 5-6 from the optic tectum contralateral to the retinal ablation, which mainly represented neuropil that would come from processes of retinal ganglion cells. Tectal neuronal bodies were not stained with silver, although some neurons were surrounded by coarse granular silver deposits. In conclusion, most of calbindin molecules are present in neurons of the tectal GABAergic inhibitory circuitry, whose functioning apparently depends on the integrity of the visual input. A possible role of calbindin in the control of intracellular Ca2+ in neurons of this circuit when the visual transmission arrives to the optic tectum remains to be studied.     

Calbindin D28k and calretinin in oxytocin and vasopressin neurons of the rat supraoptic nucleus

The aim of the present study was to examine quantitatively whether two calcium-binding proteins, calbindin D28k and calretinin, are localized in oxytocin and vasopressin neurons of the supraoptic nucleus of the male rat. We used a triple-labeling immunofluorescence method with a confocal laser scanning microscope. Of the oxytocin-labeled cells, 70% were stained for both calbindin D28k and calretinin, 15% were stained for only calbindin D28k, 13% were stained for only calretinin, and 2% were stained for neither protein. Of the vasopressin-labeled cells, 73% were stained for neither calbindin D28k nor calretinin, 21% were stained for only calbindin D28k, 4% were stained for only calretinin, and 2% were stained for both proteins. Calbindin D28k and calretinin have been shown previously to contribute to calcium homeostasis by buffering [Ca2+]i. Therefore, these findings suggest that most of the oxytocin neurons may have a higher Ca(2+)-buffering capacity than most of the vasopressin neurons.     

Cerebellar localization and colocalization of GABA and calcium binding protein-D28K

Immunocytochemical studies using antibodies raised against the inhibitory neurotransmitter, gamma-aminobutyric acid (GABA) and against the 28 Kd vitamin D dependent calcium binding protein (calbindin) in the cerebellum, are reviewed. The GABA immunoreactive neurones found in the cerebellar cortex were the Purkinje cell (PC), the three classes of intrinsic inhibitory interneurones, stellate, basket and Golgi cells and the cells of Lugaro. Some of the neurons of the cerebellar nuclei were also found to be GABA immunoreactive. A part of these could be identified as extrinsic neurones projecting either back to the cerebellar cortex, or to the inferior olive, both these pathways being topographically highly organized but arising from independent parent neurons. The presumed inhibitory function of these two pathways are discussed. Calbindin immunoreactivity in the cerebellum was confined to the PCs, staining concerned the whole cell including soma, branching dendrites, axons and axons terminals. The antibody, which appears to be tightly bound to the PC in vivo, failed to stain some of the PC when cerebellar slices maintained in vitro were studied. The stability of the antigen-antibody binding and the use of calbindin as a marker specific for the PC in the cerebellum, is discussed. Co-localization of GABA with calbindin as well as with other calcium binding proteins are reported to be found in the PCs. While these co-localizations have led to much speculation, conclusive functional roles for them have not been identified at present.     

Non-pyramidal neurons of layers I-III in the dog's cerebral cortex (parietal lobe). A Golgi survey

In an attempt to classify neurons in the upper layers of the cerebral cortex according to modern nomenclature based on Golgi impregnations, non-pyramidal neurons in layers II and III of the dog's cerebral cortex have been categorized into thirteen types: large double-bouquet cells with long ascending and descending axons (type I double-bouquet cells); bipolar neurons; multipolar neurons with long tufted descending axons (type II double-bouquet cells); neurons with long ascending axons; neurons with superficial axon plexuses; elongated large multipolar neurons with extended generalized axonal arborizations; neurons with long descending axons; small bi-tufted neurons with short ascending, descending or local axons; small multipolar neurons with short ascending, descending or local axons; multipolar neurons with local or extended axonal arborizations usually forming arcades (some of them also with a long descending axon); basket cells; neurogliaform neurons, and chandelier cells. Neurons in the molecular layer were horizontal cells and multipolar neurons with short axons. These data have been compared with those described in other species to provide a provisional classification of non-pyramidal neurons located in the upper layers of the cerebral cortex.     

Open field stress and neurons containing calcium-binding proteins in the piriform cortex of the rat.

In the present study we wanted to check whether the expression of the c-Fos protein (the marker of cellular activity) appears in cells containing calcium-binding proteins (CaBPs) in animals exposed to the open field test. Eight adult Wistar rats were examined. In the first step the open field test was applied throughout 10 minutes. After perfusional fixation brains were frozen and cut on the cryostat in the coronal plane and stained with the standard immunohistochemical method. Sections were double stained for c-Fos and CaBPs: parvalbumin (PV), calbindin (CB), calretinin (CR). c-Fos positive cells were localized predominantly in layers II and III of the piriform cortex (PC). The double labeling study showed that neurons containing CaBPs are rarely c-Fos-immunoreactive. Often PV-positive and CB-positive fibers surround c-Fos-positive neurons in layers II and III in a form of a basket. It seems that cells containing CaBPs are not directly involved in the response to aversive stimuli but cells containing those calcium-binding proteins might influence directly c-Fos positive neurons of PC.     

Neurotransmitters, neuropeptides and calcium binding proteins in developing human cerebellum: a review

Many endogenous neurochemicals that are known to have important functions in the mature central nervous system have also been found in the developing human cerebellum. Cholinergic neurons, as revealed by immunoreactivities towards choline acetyltransferase or acetylcholinesterase, appear early at 23 weeks of gestation in the cerebellar cortex and deep nuclei. Immunoreactivities gradually increase until the first postnatal month. Enkephalin is localized in the developing cerebellum, initially in the fibers of the cortex and deep nuclei at 16–20 weeks and then also in the Purkinje cells, granule cells, basket cells and Golgi cells at 23 weeks onward. Another neuropeptide, substance P, is localized mainly in the fibers of the dentate nucleus from 9 to 24 weeks but substance P immunoreactivity declines thereafter. GABA, an inhibitory neurotransmitter of the central nervous system, starts to appear at 16 weeks in the Purkinje cells, stellate cells, basket cells, mossy fibers and neurons of deep nuclei. GABA expression is gradually upregulated toward term forming networks of GABA-positive fibers and neurons. Catecholaminergic fibers and neurons are also detected in the cortex and deep nuclei at as early as 16 weeks. Calcium binding proteins, calbindin D28K and parvalbumin, make their first appearance in the cortex and deep nuclei at 14 weeks and then their expression decreases toward term, while calretinin appears later at 21 weeks but its expression increases with fetal age. The above findings suggest that many neurotransmitters, neuropeptides and calcium binding proteins (1) appear early during development of the cerebellum; (2) have specific temporal and spatial expression patterns; (3) may have functions other than those found in the mature neural systems; and (4) may be able to interact with each other during early development.     

Calbindin D28k in mammalian intestinal absorptive cells: immunohistochemical evidence

Calbindin D28k and D9k are two cytosolic calcium-binding proteins abundant in intestinal absorptive cells which appear to play a role in calcium translocation. Until today, calbindin D28k was found in avian and reptilian absorptive cells but not in mammalian ones. We have described the presence of calbindin D28k-immunoreactivity in intestinal absorptive cells of pig and jerboa (Jaculus jaculus). Pig calbindin D28k-immunoreactive absorptive cells were prominent in duodenum, they were scattered along the villi and nearly absent in the crypts. Jerboa labelled absorptive cells were located along the colonic mucosal surface. No calbindin D28k could be detected in mouse, rat and goat absorptive cells. Topography of calbindin D28k absorptive cells was compared with calbindin D9k distribution. Our results confirmed the data of the literature showing a gradient of labelling increasing from the crypt to the top of the villus and no positive endocrine cell. Young (48 h old) pigs did not expressed calbindin D28k in absorptive cells although calbindin D9k was detected. Calbindin D28K was also observed in endocrine cells which were numerous in pig and goat duodenum and very rare in mouse and jerboa. Western blot experiments confirmed the presence of calbindin D28k in the adult pig intestine, in the jerboa colon and the absence of cross-reactivity between calbindin D28k antibody and calbindin D9k.     

Parvalbumin,calbindin, and calretinin mark distinct pathways during development of monkey dorsal lateral geniculate nucleus

Immunocyochemical labeling was applied to follow the developmental changes in the calcium-binding proteins parvalbumin (PV), calbindin D28k (CaB), and calretinin (CaR) during fetal and infant development of Macaca monkey dorsal lateral geniculate nucleus (LGN). For all three proteins, LGN cell body and retinal ganglion cell (RGC) axon labeling patterns changed temporally and spatially over development, and many of these were LGN laminar specific. CaR+ and CaB+ cells were present at the youngest age studied, fetal day 55 (F55). After lamination of the LGN occurred between F90 and F115, CaR+ and CaB+ neurons were specific markers for the S, intercalated, and interlaminar layers. Double label immunocytochemistry showed that all CaR+ cells contained CaB, and none contained GABA. CaR+ cell bodies decreased in number soon after birth so that adult LGN contained only a very small number of CaR+ cells. These patterns and cell counts indicated that a downregulation of CaR had occurred in the CaB+ population. Although CaB+ cell density in S and interlaminar zones declined in the adult, cell counts indicated that this is due to dilution of a stable population into a much larger nucleus during development. PV+ cells appeared at F85 only within the putative magnocellular (M) and parvocellular (P) layers, and PV remained a marker for these layers throughout development. Fetal PV cells also contained GABA, indicating that they were LGN interneurons. After birth, GABA−/PV+ cell numbers increased dramatically throughout the whole nucleus so that by the end of the first year, P and M layers were filled with PV+ cells. Their number and size indicated that these were the LGN projection neurons. Beginning at F66, bundles of PV+ axons occupied the anterior-middle LGN and filled the optic tract. Up to F101, PV+ synaptic terminals were restricted to P layers, but after F132 labeling in M layers was heavier than in P layers. Axonal labeling for CaR began at F125. Prenatally CaR+ terminals were present mainly in P layers, whereas by postnatal 9 weeks labeling in M layers much exceeded P layers. Axonal labeling for CaB was present at F132, but CaB+ terminals were observed only after birth with labeling always heavier in M than P layers. By postnatal 9 weeks, PV, CaR, and CaB were colocalized in the same axons and terminals. These experiments indicated that during development and in the adult LGN, both CaR and CaB were markers for the LGN neurons in the S and intercalated pathway. CaR was present transiently while CaB persisted into adulthood. PV was a M and P layer marker first for interneurons and later for projection cells. The complex temporal developmental patterns found in this study suggested that viewing PV, CaB, and CaR simply as calcium-buffering proteins severely underestimates their functional roles during visual system maturation. © 1996 John Wiley & Sons, Inc.     

Distribution of calcium-binding proteins parvalbumin and calbindin in the pigeon telencephalic auditory center

Immunoreactivity for calcium-binding proteins parvalbumin (PV) and calbindin (CB) was studied in the pigeon (Columba livia) telencephalic auditory center. All its regions displayed overlapping distribution patterns of PV and CB immunoreactivity, although in the central (L2) vs. peripheral (L1, L3, CMM) layers they were dissimilar. L2 and the inner L1 sublayer (L1i) were distinguished by a higher immunoreactivity of neuropil for both proteins and the presence (in L2) of numerous small densely packed granular-type cells: heavily stained PV-ir and, as a rule, poorly stained CB-ir neurons. In Lli, the number of neurons and the density of neuropil immunoreactive to both proteins decreased. The outer L1 sublayer (L1e) as well as L3 and CMM were characterized by a generally lesser density and irregular distribution of immunoreactive neuropil and a heterogenous repertoire of PV-ir and CB-ir neurons referring to diverse morphological types, with an increased number of large multipolar cells. The differences in PV and CB immunoreactivity among different regions of the pigeon telencephalic auditory center revealed the similarity of the latter to the laminar auditory cortex in mammals.     

Neurogliaform cells: neurochemistry, spatial arrangement, and their role in the neocortical inhibitory system

The neurogliaform cells (NGFC) localized in area 4 of the human motor cortex were found to express choline acetyl transferase (ChAT), GABA, and calbindin. ChAT-positive neurons were located in cortical layer II. Their dendrites lay in a close proximity to those of pyramid cells, neighbouring neurogliaform cells, and bodies and dendrites of other cortical neurons. The NGFCs revealed by Golgi staining fell into two groups. Cells of the first group had locally (within cortical layer II) spreading axons, while those of the second group had axons extending into the adjacent layers. Neurochemical heterogeneity of NGFCs is discussed in the context of information processing in cortical modules and interaction of excitatory and inhibitory interneurons.