1-Naphthol basic dye (1-NBD). An alternative to diaminobenzidine (DAB) in immunoperoxidase techniques

A half century of experimental neuroanatomical tracing

Most of our current understanding of brain function and dysfunction has its firm base in what is so elegantly called the 'anatomical substrate', i.e. the anatomical, histological, and histochemical domains within the large knowledge envelope called 'neuroscience' that further includes physiological, pharmacological, neurochemical, behavioral, genetical and clinical domains. This review focuses mainly on the anatomical domain in neuroscience. To a large degree neuroanatomical tract-tracing methods have paved the way in this domain. Over the past few decades, a great number of neuroanatomical tracers have been added to the technical arsenal to fulfill almost any experimental demand. Despite this sophisticated arsenal, the decision which tracer is best suited for a given tracing experiment still represents a difficult choice. Although this review is obviously not intended to provide the last word in the tract-tracing field, we provide a survey of the available tracing methods including some of their roots. We further summarize our experience with neuroanatomical tracers, in an attempt to provide the novice user with some advice to help this person to select the most appropriate criteria to choose a tracer that best applies to a given experimental design.

Protein SP40,40-like Immunoreactivity in the Rat Brain: Progressive Increase With Age

The pattern of distribution of SP40,40-like immunoreactive structures has been studied in the rat brain using a well-characterized polyclonal antibody raised against the SP40,40 protein. Protein SP40,40 is the human counterpart of the rat sulphated glycoprotein 2, whose mRNA shows widespread expression in the developing and mature brain. In young adult rats few immunoreactive structures were observed. Some immunoreactive neurons were found in the cingulate cortex, the arcuate and perifornical hypothalamic nuclei, as well as glial labelling in the hypothalamus. A striking increase in the number of immunoreactive cells was observed as a function of age. In 20 - 22-month-old rats, numerous immunoreactive cells were observed in the cingulate cortex, several thalamic and hypothalamic nuclei, the red nucleus, olivary nuclei, superior colliculus, and many cranial nerve nuclei. Whereas the immunoreactivity was restricted to a diffuse labelling of the cell bodies and processes in young rats, other forms of labelling were observed in aged rats: punctate cytoplasmic labelling and intensely stained granules with no visible cell membrane. A further increase in the density of the immunoreactive material was observed in 30 - 31-month-old rats. Double labelling experiments demonstrated that the SP40,40 immunoreactivity was almost exclusively located in neurons and not in glial cells (with the exception noted above). The distribution of SP40,40 immunoreactivity in aged rats did not coincide with the distribution of the microtubule-associated tau protein, OX42 or lipofuscin.

Use of peroxidase substrate Vector VIP for multiple staining in light microscopy

The study of the distribution of a fiber input to a particular brain area and the visualization of the anatomical relationships of that input with both projection- and interneurons, requires a triple-staining that allows the unequivocal distinction of each of the three components in one and the same histological section. In this regard, we investigated the properties of a recently introduced peroxidase chromogen, VIP (V-VIP; Vector Labs) in combination with two traditional substrates, standard diaminobenzidine (DAB, brown precipitate) and nickel-enhanced DAB (DAB-Ni, black). In rats, the anterograde tracer biotinylated dextran amine (BDA) and the retrograde tracer fluorogold (FG) were injected in the perirhinal cortex and hippocampus, respectively. Transported BDA was detected with an avidin-biotin-peroxidase complex, whereas the transported FG was detected via a PAP method. Tracing with BDA and FG was combined with parvalbumin- or calbindin-immunocytochemistry. We compared various combinations and staining sequences. The best results were obtained with a staining sequence comprising first the BDA stain with DAB-Ni as chromogen, second the FG protocol with the chromogen DAB and finally, parvalbumin- or calbinding-immunocytochemistry using the chromogen V-VIP. The order with which the chromogens were applied appeared to be critical. Partial or even total loss of V-VIP reaction product has been observed after standard dehydration in ethanol. As an alternative, a quick dehydration procedure in toluene yields much better staining. Colour separation is excellent and the sensitivity is high. This procedure may also be used for detection of any other combination of three different labels, taking the usual care to avoid cross-reactivity between antibodies.

Digoxigenylated primary antibodies for sensitive dual-peroxidase labelling of neural markers

This study extends the application of the digoxigenin-anti-digoxigenin (DIG) technique to immunocytochemistry by using digoxigenin-tagged primary antibodies. Certain features of this technique when applied to non-radioactive in situ hybridization, such as the absence of endogeneous digoxigenin immunoreactivity in animal tissues, seem to be advantageous also for its application to immunocytochemistry. Thus, the present work is focused on dual-peroxidase staining experiments based on digoxigenylated antibodies directed against glial fibrillary acidic protein, parvalbumin, and calbindin, in a straightforward combination with conventional cytochemical methods. The protocols include the concomitant detection of two antigens, for which only primary antibodies from one animal species are available, with differently haptenized antibodies (e.g., biotinylated anti-calbindin and digoxigenylated anti-parvalbumin). The versatility of the DIG technique is exemplified by the combination of lectin and immunocytochemical procedures for the detection of astrocytes and microglia, and the simultaneous visualization of perineuronal nets and parvalbumin-containing neurons in the rat brain.

Multiple anterograde tracing, combining Phaseolus vulgaris leucoagglutinin with rhodamine- and biotin-conjugated dextran amine

The simultaneous use of different neuroanatomical anterograde tracers provides a potentially powerful method to study the convergence of afferent systems in a particular brain area. However, a simple routine procedure to apply multiple anterograde tracers in conjunction with their simultaneous visualization is still missing. We report an easy and straightforward application of three sensitive anterograde tracers: Phaseolus vulgaris leucoagglutinin (PHA-L), rhodamine-conjugated dextran amine (RDA) and biotin-conjugated dextran amine (BDA). These tracers can be visualized simultaneously and permanently through a triple-staining procedure with nickel-enhanced diaminobenzidine (DAB-Ni), DAB and 1-naphthol/Azur B as chromogens. Our test model comprised the projections from the nucleus reuniens thalami and entorhinal cortex. Both projection systems show a high degree of overlap in their terminal fields in the hippocampus. Two tracers were injected in the left and right entorhinal cortex, respectively; a third tracer was injected in the nucleus reuniens. This combination of injections provided a good opportunity to compare the three tracers in one and the same animal. PHA-L, RDA and BDA, injected in either of the injection sites, turned out to be equally sensitive and revealed the morphology of the involved projection systems in great detail. The triple-staining protocol yielded an excellent, simultaneous detectability of the three tracers with a remarkably low background level. Thus, the combination of the anterograde tracers PHA-L, RDA and BDA, in conjunction with the triple-staining procedure, offers a very attractive approach for neuroanatomical research.

Calbindin-D28K (CaBP28k)-like Immunoreactivity in Ascending Projections

This study concerns the involvement of calbindin-D28K (CaBP28k)-containing neurons in the efferent projections of both the trigeminal nucleus caudalis and the dorsal vagal complex (nucleus of the solitary tract and area postrema) in rats. Recent evidence has shown that these projections are particularly important for the processing of visceroception and/or nociception at central levels. The trigeminal nucleus caudalis has dense projections to both the nucleus of the solitary tract and the parabrachial area; the dorsal vagal complex is intimately connected to the parabrachial area. CaBP28k is a calcium-binding protein the function of which could be a determining factor in controlling the excitability of cells by acting on intrinsic calcium metabolism. CaBP28k content of projections was ascertained using a double labelling approach that combined the retrograde transport of a protein - gold complex to identify projection cells and immunocytochemistry to identify CaBP28k-positive cells. The trigeminal nucleus caudalis is rich in both CaBP28k-immunoreactive cells and cells projecting to the parabrachial area or the nucleus of the solitary tract. Cells containing both the protein and the retrograde tracer, however, were mostly restricted to the superficial layers (laminae I and outer II) and to their rostral extensions, the dorsal paramarginal and paratrigeminal nuclei. These trigeminal subdivisions are targets for nociceptive, visceroceptive and thermal inputs of peripheral origins. The dorsal vagal complex is rich in CaBP28k. Dense populations of immunoreactive cells are observed in the ventrolateral part of the area postrema and all of the three main subdivisions of the nucleus of the solitary tract (rostral gustatory, ventrolateral respiratory and medial cardiovascular subregions). The subnucleus commissuralis, subnucleus centralis and dorsal subnuclei are particularly densely stained. The subnucleus centralis, which is involved in regulating food and water intake, does not project to the parabrachial area. The area postrema, subnucleus commissuralis and dorsal subnuclei, which are implicated in cardiovascular and/or ingestive behaviours, have dense projections to the parabrachial area, many of which contain CaBP28k. The present results demonstrate that CaBP28k-containing cells form a major part of the solitary and trigeminal projection systems, including subregions that are involved in visceroception and/or nociception processing. The location of solitary nucleus projection cells overlaps those of some neuropeptidergic projecting populations, suggesting colocalization. Consequently, certain neuropeptidergic actions may be CaBP28k-dependent.

Temporal differentiation and migration of substance P, serotonin, and secretin immunoreactive enteroendocrine cells in the mouse proximal small intestine

Precise spatial interrelationships exist between substance P, serotonin, and secretin containing enteroendocrine cells in the gastrointestinal tract of mice. In the proximal small intestine these products are coexpressed in various combinations in single enteroendocrine cells along the crypt to villus axis in a pattern that suggests the sequential expression of substance P, serotonin, and secretin. In this report we use bromodeoxyuridine (BrdU) and multilabeling immunohistochemistry to define the temporal and spatial interrelationships between substance P, serotonin, and secretin immunoreactive cells in the mouse proximal small intestine. Our findings demonstrate the sequential expression of substance P, serotonin, and secretin in a population of upwardly migrating enteroendocrine cells and, furthermore, identify a population of crypt associated cells coexpressing substance P and serotonin that fails to traverse this pathway. The lack of secretin immunoreactive cells in the crypts suggests that local factors present in the crypts and/or on villi regulate secretin expression. The combined use of BrdU and multilabeling immunohistochemistry provides a method for defining enteroendocrine cell differentiation pathways throughout the gastrointestinal tract.

c-fos expression in rat lumbar spinal cord during the development of adjuvant-induced arthritis

A parallel clinical and behavioral study of adjuvant-induced arthritis in the rat showed four stages in the time-course of the disease: preclinical (first week), acute (weeks 2-4), post-acute (weeks 5-8) and recovery weeks 9-11) [Calvino et al. (1987) Behav. Brain Res. 24, 11-29]. As several studies have reported the expression of the proto-oncogene c-fos in spinal cord neurons following acute noxious peripheral stimuli, the aim of this study was to quantitatively assess Fos-like immunoreactivity in lumbar spinal cord neurons at various times of adjuvant-induced arthritis development, i.e. one, two, three, 11 and 22 weeks post-inoculation. The total number of Fos-like immunoreactive neurons in the lumbar enlargement correlated with the observed development of adjuvant-induced arthritis, i.e. Fos-like immunoreactivity was absent at one week, moderate at two weeks, greatly increased at three weeks, decreased at 11 weeks and returned to control values at 22 weeks. At three weeks, at the peak of Fos-like immunoreactivity distribution and acute stage of hyperalgesia, maximal labeling was observed in L3 and L4 spinal segments. In these segments, the most densely labeled region was the neck (laminae V and VI) of the dorsal horn (55%) and the ventral horn (35%) as compared to the superficial laminae (laminae I and II; 5%) and the nucleus proprius (laminae III and IV; 5%). These data indicate that c-fos expression induced by chronic inflammation is better expressed in deeper laminae than in the superficial ones, and that the number of Fos-positive cells correlates with behavioral studies.(ABSTRACT TRUNCATED AT 250 WORDS)

Fos-like immunoreactivity in the rat superficial dorsal horn induced by formalin injection in the forepaw: effects of dorsal rhizotomies

As previously described at the lumbar spinal level, we found that 2 h after subcutaneous formalin injection in the distal part of the fore-limb, Fos-like immunoreactivity (FLI) was induced in the ipsilateral cervical enlargement. Not surprisingly, as the injection site corresponds to the distal part of the C6-C8 dorsal root dermatomes, maximal labelling which predominated in the superficial laminae, was observed in the C6-C8 segments and to a lesser extent in C5. Similar experiments were performed on rats which underwent various types of unilateral dorsal rhizotomies (DRh) 7 days before formalin injection. In animals with C4, C5, T1 and T2 DRh sparing C6-C8 the rostrocaudal distribution was similar to the intact one. But, in animals having C4-T2 DRh sparing one single root, C7, the segmental FLI distribution was modified: it was slightly increased in C7, decreased in C6 and significantly decreased in C8. As expected, no FLI was found in animals with C4 to T2 DRh. The spared root model provides information about the segmental distribution in the cervical spinal cord of the input brought by a single root following stimulation of the distal forelimb, i.e., maximal distribution in the entry segment, but also in the two rostral and one caudal segments.

A double immunocytochemical and histochemical technique for demonstration of cholinergic neurons and microglial cells in basal forebrain and neostriatum of the rat

Cholinergic neurons, and their relationship to microglial cells, have been examined by light and electron microscopy with an immunocytochemical and histochemical double-staining technique, in medial septum, diagonal band of Broca, nucleus basalis and neostriatum. This technique may be applied to experimental models of anterograde and retrograde degeneration of the cholinergic neurons of the basal forebrain in order to collect further information relative to the aetiology of degenerative diseases such as Alzheimer's disease.

Nerve growth factor receptor and choline acetyltransferase colocalization in neurons within the rat forebrain: response to fimbria-fornix transection

Although it is well known that magnocellular cholinergic basal forebrain neurons are trophically responsive to nerve growth factor (NGF) and contain NGF receptors (NGFr), the exact distribution of forebrain NGFr-immunoreactive neurons and the degree to which cholinergic neurons are colocalized with them have remained in question. In this study we employed a very sensitive double-labelling method and examined in the same tissue section the distribution and cellular features of NGFr-positive and choline acetyltransferase (ChAT)-immunolabelled neurons within the rat basal forebrain. Throughout this region the majority of magnocellular basal forebrain neurons were immunoreactive for both NGFr and ChAT. However, a small percentage of neurons in the ventral portion of the vertical limb of the diagonal band of Broca were immunoreactive only for NGFr, whereas a larger population of magnocellular neurons in the substantia innominata exhibited only ChAT immunoreactivity. No NGFr-immunoreactive cells were found associated with ChAT-positive neurons in the striatum, neocortex, or hippocampus, and no single-labelled NGFr-immunoreactive neurons were found outside the basal forebrain area, except for a large number of positive-labelled cells along the ventricular walls of the third ventricle. In addition to its function in maintaining the normal integrity of the basal forebrain and cholinergic, peripheral sympathetic, and neural-crest-derived sensory neurons, NGF may also have a role in the growth of these neurons after damage to the nervous system. To examine this postulate the hippocampus was denervated of its septal input and examined 8 weeks later. Two populations of neurons were found to have undergone collateral sprouting--namely, the midline magnocellular cholinergic neurons of the dorsal hippocampus and the sympathetic noradrenergic neurons of the superior cervical ganglion. Both of these neuronal populations also stained strongly for NGFr. In contrast, the small intrinsic cholinergic neurons of the hippocampus exhibited neither sprouting response nor staining for NGFr. In view of these results, we suggest that the differing sprouting responses demonstrated by these three neuronal populations may be due to their responsiveness to NGF, as indicated by the presence or absence of NGF receptors.

The vascular response to tumor infiltration in malignant gliomas. Morphometric and reconstruction study

Neo-vascularization and endothelial hyperplasia have been shown to be very active in malignant gliomas. In this contribution the vascularization of the cortex infiltrated by malignant gliomas is morphometrically studied and the endothelial proliferations are immunohistochemically investigated and reconstructed by a three-dimensional computer-assisted procedure. Vessel density increases after tumor infiltration in some cases only. The diameter of vessels increases and so does the number of nuclei/vessel after the complete invasion of the cortex when vascular glomeruli develop. In completely infiltrated cortex with development of glomeruli and circumscribed necroses, vessel density is very low. No neoformation of vessels takes place before the complete infiltration of the cortex by the tumor. The hyperplastic formations, usually arranged parallel to the deep or outer cortical layers, take origin from the radially penetrating vessels from the meninges and their lateral branching. The hyperplasia deforms the vascular network, making it often inadequate to supply tumor cells. Immunohistochemically, the cells composing the hyperplastic structures are variably positive for factor VIII/RAg and, at a lesser extent, for alpha-smooth muscle actin. The poorness of the vascular network in many instances of completely infiltrated cortex is responsible for the development of circumscribed necroses.

Identification of L-dopa-dopamine and L-dopa cell bodies in the rat mesencephalic dopaminergic cell systems

An immunocytochemical technique for simultaneously visualizing two different antigens, dihydroxyphenylalanine (L-DOPA) and dopamine (DA), has been used to investigate the presence of cell bodies containing both compounds L-DOPA and DA and those having only L-DOPA in rat mesencephalon areas. The brain slices were processed with a double peroxidase-antiperoxidase method using simultaneously an incubation of a rabbit anti-L-DOPA serum and a monoclonal anti-DA antibody raised in mouse. Both antigens were revealed by the peroxidase reaction but with different chromogens that are easily distinguishable. In this staining procedure, the first antigen, conjugated DA was stained using the 3,3'-diaminobenzidine (DAB)-Nickel complex; while the second antigen, conjugated L-DOPA, was localized using DAB. The yellow-brown color due to DAB was masked by that of DAB-nickel. The possible existence of both single and double labelings could be worked. We have found many L-DOPA-positive/DA-positive and a few L-DOPA-positive/DA-negative cell bodies in dopaminergic regions in the rat midbrain: substantia nigra, ventral tegmental area, and raphe nuclei. In the locus coeruleus, we noted only L-DOPA-positive/DA-positive cell bodies. These results confirm those previously described for rat and cat hypothalamus, where both immunoreactive-cell body types have been detected: L-DOPA positive/DA positive and L-DOPA positive/DA negative. The existence of neuronal cells containing only L-DOPA is a new neuroanatomic finding, accounting better for the heterogeneity of dopamine systems with respect to physiologic, pharmacologic, and molecular data.

Simultaneous detection of indoleamines and dopamine in rat dorsal raphe nuclei using specific antibodies

Using a monoclonal antibody against dopamine and a rabbit antiserum against serotonin, 5-methoxytryptamine or tryptamine, we were able to achieve the simultaneous localization of two amines in glutaraldehyde-fixed sections of rat dorsal raphe nuclei. In this staining procedure, the first antigen was localized using 3,3'-diaminobenzidine (DAB), while the second antigen was stained using the 1-naphthol basic dye (2-NBD) method. The two antigens were localized in different cells or structures. No overlap of the staining was observed, thus indicating that dopamine is not localized with serotonin, 5-methoxytryptamine or tryptamine.

Glial fibrillary acidic protein and vimentin in the experimental glial reaction of the rat brain

Glial reaction has been studied in the rat by the immunohistochemical demonstration of glial fibrillary acidic protein (GFAP) and vimentin (VIM) in two experimental conditions. The first was represented by a necrotic cerebral lesion obtained by laser irradiation and the second by the development of experimental tumors induced by transplacental ethylnitrosourea. Reactive astrocytes develop not only in the proximity of the lesion but also distant from it. The intensity of the glial response seems to depend upon the normal distribution of astrocytes and the perilesional edema. GFAP decorates all the reactive astrocytes, whereas VIM is positive only in those at the edges of the lesion. The significance of the different responses in the two models and between the two intermediate filaments is discussed.

Immunohistochemical demonstration of vimentin in human cerebral tumors

The distribution of vimentin (VIM) has been histochemically investigated in 53 cerebral tumors and compared in gliomas to that of glial fibrillary acidic protein (GFAP). In gliomas VIM is less positive than GFAP, but shows the same distribution. It cannot be considered as indicating immaturity of glial tumor cells. VIM is also positive in glial processes of cerebellar pilocytic astrocytomas, in Schwann cells of neurinomas and in endothelial cells of all oncotypes. In medulloblastomas, VIM decorates reactive glia cells. A diffuse positive reaction has been observed in meningiomas. In hemangioblastomas, besides intervascular and endothelial cells, groups of polygonal cells are intensely positive for both VIM and GFAP. The interpretation of VIM in cerebral tumors is largely based on the distribution patterns of this intermediate filament in the developing CNS of rodents.

Simultaneous and successive localization of two antigens in the same tissue section using 3,3'-diaminobenzidine and 1-naphthol basic dye

We describe two procedures for the simultaneous and successive localization of two antigens in the same tissue section. In the simultaneous staining procedure, the first antigen was localized using 3,3'-diaminobenzidine (DAB), while the second antigen was stained using the 1-naphthol basic dye (1-NBD) method. The colour of the second antigen depended on the basic dye used, and no mixing of colours was observed when the two antigens were localized in different cells or structures. However, sequential double staining proved to be more convenient for the demonstration of two antigens in the same cell. In this procedure, the first antigen was stained using 1-NBD, and the interesting microscopic fields were photographed. The basic dye was then completely removed, and the second antigen was stained using DAB.