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Colocalization of atriopeptin-like immunoreactivity with choline acetyltransferase- and substance P-like immunoreactivity in the pedunculopontine and laterodorsal tegmental nuclei in the rat.

Atriopeptin, the atrial natriuretic peptide, is a circulating hormone that plays an important role in the regulation of fluid and electrolyte balance. Immunohistochemical studies have shown that large, multipolar atriopeptin-like immunoreactive (APir) neurons are present in areas of the midbrain corresponding to the large neurons of the pedunculopontine tegmental (PPT) and lateral dorsal tegmental (TLD) nuclei, all of which can be stained immunohistochemically for choline acetyltransferase-like immunoreactivity (ChATir). A subpopulation of these cholinergic PPT and TLD neurons are also known to contain substance P-like immunoreactivity (SPir). Using an immunofluorescent technique that allows simultaneous localization of two antigens, we have studied the relationship between APir, SPir and ChATir in the pontine tegmentum of the rat. We have found that the large multipolar APir neurons of the pontine tegmentum are identical to the ChATir neurons of the PT and TLD nuclei and a subpopulation of the APir neurons in PPT and TLD neurons are also SPir.

Animals↗

Intragranular colocalization of CRF and Met-Enk-8 in nerve terminals in the rat median eminence.

The ultrastructural localizations of rat corticoliberin (rCRF) and methionine-enkephalin octapeptide (Met-Enk-8) in the external layer of the rat median eminence were examined by double-immunogold labeling with anti-rCRF and anti-Met-Enk-8 sera labeled with small-sized (Gs) and medium-sized (Gm) gold particles, respectively. Two types of immunolabeled terminals were distinguished: one type with small granules (70 nm) labeled with Gs, and the other with large granules (100 nm) labeled with Gm. In both types, however, some granules were labeled with both Gs and Gm.

Animals↗

Colocalization of immunoreactive substance P and neurotensin in amacrine cells of the goldfish retina.

Using an immunohistochemical double-label technique, neurotensin and substance P immunoreactivity were localized to amacrine cells in the goldfish retina. Both peptides were found in a single population of unistratified amacrine cells branching in sublamina 3 of the inner plexiform layer. A monostratified amacrine cell branching in sublamina 1 contained only substance P immunoreactivity and a bistratified cell branching in sublaminae 1 and 3 contained only neurotensin immunoreactivity.

Animals↗

Melanin-concentrating hormone (MCH) is colocalized with alpha-melanocyte-stimulating hormone (alpha-MSH) in the rat but not in the human hypothalamus.

Melanin-concentrating hormone (MCH)-containing neurons have recently been localized in the dorsolateral region of the rat hypothalamus, an area where the second alpha-MSH system is found which contains only alpha-MSH and none of the pro-opiomelanocortin (POMC)-related peptides. In order to study the morphological relationships between the MCH and alpha-MSH neuronal systems, we have studied the immunocytochemical localization of both MCH and alpha-MSH in the rat hypothalamus. The same study was also performed in the human hypothalamus where there is only one alpha-MSH system which contains alpha-MSH as well as the other POMC-related peptides (first alpha-MSH system). In the rat dorsolateral hypothalamus, we could demonstrate that most neuronal cell bodies stained for MCH also contained immunoreactive alpha-MSH. In the human hypothalamus, neuronal cell bodies stained for MCH were observed only in the periventricular area whereas cell bodies containing alpha-MSH were exclusively located in the infundibular (arcuate) nucleus. In the rat, immunoelectron microscopy showed labelling for MCH in the dense core vesicles of positive neurons and double-staining techniques clearly demonstrated that both immunoreactive MCH and alpha-MSH could be consistently detected in the same dense core vesicles. These ultrastructural studies then suggest that these two peptides should be released simultaneously from neurons located in the rat dorsolateral hypothalamus.

Animals↗

Catecholamine and serotonin colocalization in projection neurons of the area postrema.

A large population of the rat area postrema (AP) neurons which project to the parabrachial area (PBA) are serotonergic. Many AP neurons contain tyrosine hydroxylase (TH) and are presumed to be noradrenergic. However, it was not previously known whether TH-containing AP neurons also have projections to the PBA. TH-containing and serotonin (5-HT)-containing neurons have wide and overlapping distributions within the AP, and it was therefore possible that TH and 5-HT may be contained within the same AP neurons. In the present study immunohistochemical and retrograde axonal transport techniques were combined to determine whether TH-containing AP neurons project to the PBA and whether TH and 5-HT coexist in AP neurons. Adult male rats were given bilateral injections of the retrograde transport tracer, True blue (TB), into the PBA. After a 4-day survival period, vibratome sections of the caudal brainstem were processed for both TH and 5-HT immunohistochemistry. Examination of the sections revealed that over 25% of the 5-HT and over 30% of the TH-containing AP neurons were retrogradely labelled with TB. More surprising were our findings that many AP neurons displayed both TH and 5-HT immunoreactivity and that almost 40% of these double-labelled cells project to the PBA. Our results indicate that serotonin and noradrenaline coexist in a substantial proportion of the neurons of a major ascending viscerosensory pathway from the AP to the PBA.

Animals↗

Does cholecystokinin colocalize with dopamine in the human substantia nigra?

In situ hybridization was used to examine the distribution of neurons containing cholecystokinin (CCK) mRNA in human, monkey and rat brain. In rat and monkey brain CCK mRNA was visualized in the substantia nigra pars compacta and in the ventral tegmental area. The dopaminergic cell bodies in the human substantia nigra did not however show detectable amounts of CCK mRNA. Low levels of CCK mRNA were observed in the nucleus paranigralis, the human equivalent of the rodent ventral tegmental area. High levels of CCK mRNA were seen in other regions of the same brains including the cortex and the hippocampus. Thus, the adult human substantia nigra dopaminergic cells, in contrast to primate and rodent substantia nigra, do not express CCK. These results question the hypothesis of an involvement of CCK in the regulation of dopaminergic neurons and help to explain the absence of decreased CCK levels in the caudate and putamen of Parkinson's disease victims.

Adult↗

Immunohistochemical markers in rat brain: colocalization of calretinin and calbindin-D28k with tyrosine hydroxylase.

Many dopaminergic cells of the substantia nigra are known to contain the calcium-binding proteins calretinin and calbindin-D28k. Catecholaminergic cell groups throughout the rat brain were therefore examined by two-colour immunofluorescence to determine whether they too contained these calcium-binding proteins as well as tyrosine hydroxylase (TH). Some TH+ cell groups are mostly positive for both calretinin and calbindin, notably in the ventral tegmental area, the interfascicular nucleus, and parts of the substantia nigra. Other TH+ cell groups in the midbrain, hindbrain and hypothalamus are very diverse; different cell groups are positive for calretinin, or calbindin, or both, or neither. In the olfactory bulb, entirely separate sets of periglomerular cells are positive for TH, calretinin and calbindin. However, there is considerable heterogeneity in calcium-binding protein expression within most cell groups, even in the substantia nigra. This could be a sign that calcium-binding proteins are regulated according to aspects of neuronal activity.

Animals↗

Colocalization of enkephalin-, glucagon-, and corticotropin-releasing factor-like immunoreactivity in GABAergic amacrine cells in turtle retina.

The large number of amacrine cells which contain gamma-aminobutyric acid (GABA) in the turtle retina makes it difficult to examine specific GABAergic cell types. In order to selectively label subpopulations of GABAergic neurons, we have used fluorescent double-labeling immunocytochemical techniques to examine the localization of GABA-like immunoreactivity (LI) in amacrine cells which contain antigens resembling the neuropeptides glucagon (GLUC), corticotropin-releasing factor (CRF) or enkephalin (ENK). GABA-LI was found in 41% of the cells with GLUC-, 100% of the cells with CRF-, and 69% of the cells with ENK-LI. There were regional differences in the presence of GABA-LI in amacrine cell populations with ENK-LI. GABA-LI was present in about 80% of the cells with ENK-LI outside of the visual streak, while only 37% of the cells within the streak had GABA-LI. Based on the distinct morphologies and regional distributions of these peptidergic amacrine cells, we conclude that they represent different subpopulations of GABAergic amacrine cells in the turtle retina. Future studies can now utilize existing information regarding the synaptic connectivity of these peptidergic amacrine cells to help delineate the functions of GABAergic amacrine cells in the turtle retina.

Animals↗

Colocalization of enkephalin and glycine in amacrine cells of the chicken retina.

The present double-label study combines enkephalin immunocytochemistry with either autoradiography of glycine high-affinity uptake or glycine immunocytochemistry to investigate the coexistence of glycine in enkephalin-amacrine cells of the chicken retina. A regional analysis revealed that the percentage coexistence of glycine high-affinity uptake in enkephalin-amacrine cells did not vary appreciably throughout the retina. Overall, 54.9% of enkephalin-amacrine cells exhibited high-affinity glycine uptake. Double-label immunofluorescence cytochemistry revealed that 52.5% of enkephalin-amacrine cells expressed glycine immunoreactivity. These double-immunolabeled cells were observed throughout the center and periphery of the retina. The present study reveals a similar percentage of chicken enkephalin-amacrine cells expressing either glycine high-affinity uptake (54.9%) or glycine immunoreactivity (52.5%) and therefore, provides supportive evidence for identifying these cells as glycinergic. The present study also suggests a functional diversity in the population of enkephalin-amacrine cells in the chicken retina relative to their coexisting/non-coexisting relationship with glycine.

Animals↗

Colocalization of calbindin-D28k with vasopressin in hypothalamic cells of the rat: a double-labeling immunofluorescence study.

By use of a double-labeling immunofluorescence method, we examined whether vasopressin-containing cells possess a calcium-binding protein, calbindin-D28k, in the hypothalamus of the rat. Subpopulations of vasopressin-containing cells varied in their ability to possess calbindin-D28k immunoreactivity in different regions. In the supraoptic nucleus, most vasopressin-immunoreactive cells were also stained for calbindin-D28k. By contrast, in the magnocellular part of the hypothalamic paraventricular nucleus, all vasopressin-labeled cells lacked calbindin-D28k. In the suprachiasmatic nucleus, no calbindin-D28k was found in vasopressin-stained cells. This study shows a further characterization of vasopressin-containing cells of the rat hypothalamus.

Animals↗

Combination of alkaline phosphatase in situ hybridization with immunohistochemistry: colocalization of calretinin-mRNA with calbindin and tyrosine hydroxylase immunoreactivity in rat substantia nigra neurons.

We describe a method to combine non-radioactive in situ hybridization using alkaline phosphatase (AP) labelled oligonucleotide-probes with immunohistochemistry on the same thin paraffin section. The simultaneous detection of calretinin-mRNA and calbindin- or tyrosine hydroxylase-like immunoreactivity in neurons of rat substantia nigra, pars compacta, was used as a test system to develop the method. Brains were fixed by perfusion with 4% paraformaldehyde and embedded in paraffin. Five-microns-thick sections were processed for non-radioactive in situ hybridization with a 33-base alkaline phosphatase conjugated synthetic oligonucleotide complementary to calretinin mRNA. After hybridization and colour reaction to visualize calretinin mRNA, sections were incubated with antibodies against calbindin D28K or tyrosine hydroxylase. Immunoreaction was visualized using the avidin-biotin-complex-technique and diaminobenzidine. As the colour of both reaction products differ markedly, the distribution of calretinin mRNA-containing neurons (purple-blue, alkaline phosphatase product) and calbindin/tyrosine hydroxylase immunopositive cells (brown peroxidase product) could be differentiated easily on the same section. Calbindin- and tyrosine hydroxylase-like immunoreactivity was found in the majority of calretinin mRNA-containing cells within the substantia nigra, pars compacta, indicating that in this nucleus a proportion of the dopaminergic neurons contain both calcium binding proteins calbindin and calretinin. In conclusion, non-radioactive in situ hybridization using alkaline phosphatase labelled oligonucleotide probes can be readily combined with immunohistochemistry.

Alkaline Phosphatase↗

Extent of colocalization of serotonin and GABA in the neurons of the rat raphe nuclei.

Previous investigations of the distribution of neurons containing both serotonin and GABA in the brainstem raphe nuclei have yielded discrepant results amongst different authors. This study attempted to clarify the distribution as well as the proportions of raphe and other brainstem neurons that contain both neurotransmitters. All the nine serotonergic cell groups known to be present in the brainstem were examined with an indirect immunofluorescence method using antibodies against serotonin and glutamic acid decarboxylase in colchicine-treated rats. Sections were incubated either simultaneously or sequentially for the two immunolabels. Brainstem neurons that were labelled for both markers were generally infrequent. Of all the serotonin cell groups in the brainstem, the nucleus raphe magnus contained the most double-labelled cells (a mean of 3.6% of a total of 625-1155 serotonin-immunoreactive cells counted in this nucleus), followed by the nucleus raphe obscurus (1.5% of a total of 220-550 serotonin-immunoreactive neurons counted). The dorsal, median and pontine raphe nuclei as well as the supralemniscal nucleus (the B9 group) contained very few double-labelled cells, which comprised a mean of 0.1-0.7% of all serotonin-immunoreactive cells in each of these nuclei. No double labelled cells were present in the caudal linear raphe nucleus or the nucleus raphe pallidus, nor in the B4 group. These results suggest that only a very small percentage of serotonergic neurons in the medullary raphe nuclei (raphe magnus and raphe obscurus) also contain GABA, whereas such cells are virtually absent in the midbrain raphe nuclei or in the non-raphe serotonergic cell groups in the brainstem.

Animals↗

Nitric oxide synthase in the hypothalamic suprachiasmatic nucleus of rat: evidence from histochemistry, immunohistochemistry and western blot; and colocalization with VIP.

Nitric oxide (NO) is a neuroactive substance of high potency. Physiological results revealed the involvement of NO in circadian regulation of rats. Since neuronal structures containing NO-synthase (NOS) were previously not found in the circadian oscillator, the hypothalamic suprachiasmatic nucleus (SCN), in this species but are present in the hamster, we investigated the distribution of NO-producing structures in the rat SCN by Western blot analysis, immunohistochemistry of NOS, and by histochemistry (NADPH-diaphorase (NADPH-d) activity of NOS). Western blot analysis of SCN homogenates from rat (and, for comparison, hamster) showed a NOS-like immunoreactive (-LI) protein band of apparent molecular mass of 150 kDa, consistent with the neuronal NOS molecule. In the rat SCN, perikarya exhibiting NADPH-d staining of NOS-LI with a complete overlapping of both were found. Double-immunofluorescence experiments revealed that NOS cells are a subgroup of the neuronal SCN population that is characterized by immunoreactivity to vasoactive intestinal polypeptide. These data provide evidence for the existence of neuronal nitric oxide synthase in the rat SCN and may explain the involvement of NO in the mediation of photic information.

Animals↗

Colocalization of GABA and glycine in the rat dorsal column nuclei.

About half the neurons in the rat dorsal column nuclei were immunopositive for glycine or for GABA; these were smaller than immunonegative neurons. In double-stained material, 29% of stained neurons were immunopositive for GABA only, and 42% for both antigens. The results resemble those reported for spinal cord laminae that receive fast-conducting primary afferents, and suggest that glycine is an inhibitory neurotransmitter in the dorsal column nuclei.

Animals↗

Ca2+/calmodulin-dependent protein kinase type IV in dorsal root ganglion: colocalization with peptides, axonal transport and effect of axotomy.

Using the indirect immunofluorescence technique, the distribution of Ca2+/calmodulin-dependent protein kinase IV (CaM kinase IV) was studied in dorsal root ganglia (DRGs) and the sciatic nerve under normal circumstances and after axotomy and nerve ligation. CaM kinase IV-like immunoreactivity (-LI) was observed mainly in small DRG neurons but also in some large ones with the immunoreactivity mainly confined to the cell nuclei and with varying levels in the cytoplasm. CaM kinase IV-LI was present in around 1/4 of all CGRP-positive neurons and in the vast majority of the somatostatin-positive neurons. The enzyme levels decreased markedly after axotomy. The enzyme was also observed in axons in the sciatic nerve and accumulated both proximal and distal to a ligation. The present results suggest that CaM kinase is not of direct importance for upregulation of neuropeptides in DRG neurons after nerve injury. In addition to a nuclear function it may also play a role in the peripheral processes of DRG neurons.

Animals↗

Colocalization of discoidin-binding ligands with discoidin in developing Dictyostelium discoideum.

The Dictyostelium discoideum lectins, discoidin I and discoidin II, and the endogenous ligands to which they bind were immunohistochemically localized in sections of this organism at successive stages of development. For these studies, an axenic strain, AX3, was grown in a macromolecule-depleted medium rather than on bacteria, which themselves contain discoidin-binding ligands. Discoidin I-binding sites (endogenous ligands) in sections of D. discoideum were concentrated in the slime coat around aggregates, whereas discoidin II-binding sites were observed in a vesicle-like distribution in prespore cells and also in spore coats. In contrast, discoidin II did not bind to the slime coat and discoidin I bound relatively poorly to prespore cells and spore coats. The distributions of the endogenous lectins themselves were the same in axenically grown cells as previously reported for cells raised on bacteria. Discoidin I was concentrated in the slime coat and around stalk cells, and discoidin II was prominent in and around prespore cells. The congruent localization of each lectin with its endogenous ligand suggests that discoidin I normally functions in association with glycoconjugates in the slime around aggregates, and discoidin II with the galactose-rich spore coat polysaccharide.

Antibodies↗

Colocalization of transforming growth factor-alpha and a functional epidermal growth factor receptor (EGFR) to the inner cell mass and preferential localization of the EGFR on the basolateral surface of the trophectoderm in the mouse blastocyst.

Results of previous studies suggested that responses of mouse blastocysts to TGF-alpha/EGF treatment are mediated by EGF receptors (EGFR) located on the apical surface of the trophectoderm (TE). We report here results of experiments using gold-labeled EGF that confirm the presence of these apically located EGFRs. In addition, immunoelectron microscopy (IEM) studies using anti-EGFR antibodies indicate that the receptor is preferentially distributed on the basolateral surface of the TE. Furthermore, the receptor is also present on the inner cell mass (ICM) and is likely to be functional, since treatment of isolated ICMs with TGF-alpha affects [35S]methionine uptake and incorporation into acid-insoluble material. IEM was also used to demonstrate that EGF, which is not synthesized by the mouse preimplantation embryo, is present in both the oviduct and the uterus. Maternally derived EGF is present in both ICM and TE cells in freshly isolated blastocysts, but is present in greatly reduced amounts following overnight culture of blastocysts in vitro. Last, IEM was also used to demonstrate that TGF-alpha is preferentially localized to the ICM and polar TE. The co-localization of TGF-alpha and functional EGFRs to the ICM and polar TE suggests potential autocrine, juxtacrine, and paracrine roles for TGF-alpha in blastocyst development.

Amino Acids↗