Immunocytochemical demonstration of the calcium-binding proteins calbindin-D 28k and parvalbumin in the subiculum, hippocampus and dentate area of the domestic pig

Cell numbers in the reflected blade of CA3 and their relation to other hippocampal principal cell populations across seven species

The hippocampus of many mammals contains a histoarchitectural region that is not present in laboratory mice and rats-the reflected blade of the CA3 pyramidal cell layer. Pyramidal cells of the reflected blade do not extend dendrites into the hippocampal molecular layer, and recent evidence indicates that they, like the proximal CA3 pyramids in laboratory rats and mice, partially integrate functionally with the dentate circuitry in pattern separation. Quantitative assessments of phylogenetic or disease-related changes in the hippocampal structure and function treat the reflected blade heterogeneously. Depending on the ease with which it can be differentiated, it is either assigned to the dentate hilus or to the remainder of CA3. Here, we investigate the impact that the differential assignment of reflected blade neurons may have on the outcomes of quantitative comparisons. We find it to be massive. If reflected blade neurons are treated as a separate entity or pooled with dentate hilar cells, the quantitative makeup of hippocampal cell populations can differentiate between species in a taxonomically sensible way. Assigning reflected blade neurons to CA3 greatly diminishes the differentiating power of all hippocampal principal cell populations, which may point towards a quantitative hippocampal archetype. A heterogeneous assignment results in a differentiation pattern with little taxonomic semblance. The outcomes point towards the reflected blade as either a major potential player in hippocampal functional and structural differentiation or a region that may have cloaked that hippocampi are more similarly organized across species than generally believed.

Production of human entorhinal stellate cell-like cells by forward programming shows an important role of Foxp1 in reprogramming

Stellate cells are principal neurons in the entorhinal cortex that contribute to spatial processing. They also play a role in the context of Alzheimer's disease as they accumulate Amyloid beta early in the disease. Producing human stellate cells from pluripotent stem cells would allow researchers to study early mechanisms of Alzheimer's disease, however, no protocols currently exist for producing such cells. In order to develop novel stem cell protocols, we characterize at high resolution the development of the porcine medial entorhinal cortex by tracing neuronal and glial subtypes from mid-gestation to the adult brain to identify the transcriptomic profile of progenitor and adult stellate cells. Importantly, we could confirm the robustness of our data by extracting developmental factors from the identified intermediate stellate cell cluster and implemented these factors to generate putative intermediate stellate cells from human induced pluripotent stem cells. Six transcription factors identified from the stellate cell cluster including RUNX1T1, SOX5, FOXP1, MEF2C, TCF4, EYA2 were overexpressed using a forward programming approach to produce neurons expressing a unique combination of RELN, SATB2, LEF1 and BCL11B observed in stellate cells. Further analyses of the individual transcription factors led to the discovery that FOXP1 is critical in the reprogramming process and omission of RUNX1T1 and EYA2 enhances neuron conversion. Our findings contribute not only to the profiling of cell types within the developing and adult brain's medial entorhinal cortex but also provides proof-of-concept for using scRNAseq data to produce entorhinal intermediate stellate cells from human pluripotent stem cells in-vitro.

Proportional loss of parvalbumin-immunoreactive synaptic boutons and granule cells from the hippocampus of sea lions with temporal lobe epilepsy

One in 26 people develop epilepsy and in these temporal lobe epilepsy (TLE) is common. Many patients display a pattern of neuron loss called hippocampal sclerosis. Seizures usually start in the hippocampus but underlying mechanisms remain unclear. One possibility is insufficient inhibition of dentate granule cells. Normally parvalbumin-immunoreactive (PV) interneurons strongly inhibit granule cells. Humans with TLE display loss of PV interneurons in the dentate gyrus but questions persist. To address this, we evaluated PV interneuron and bouton numbers in California sea lions (Zalophus californianus) that naturally develop TLE after exposure to domoic acid, a neurotoxin that enters the marine food chain during harmful algal blooms. Sclerotic hippocampi were identified by the loss of Nissl-stained hilar neurons. Stereological methods were used to estimate the number of granule cells and PV interneurons per dentate gyrus. Sclerotic hippocampi contained fewer granule cells, fewer PV interneurons, and fewer PV synaptic boutons, and the ratio of granule cells to PV interneurons was higher than in controls. To test whether fewer boutons was attributable to loss versus reduced immunoreactivity, expression of synaptotagmin-2 (syt2) was evaluated. Syt2 is also expressed in boutons of PV interneurons. Sclerotic hippocampi displayed proportional losses of syt2-immunoreactive boutons, PV boutons, and granule cells. There was no significant difference in the average numbers of PV- or syt2-positive boutons per granule cell between control and sclerotic hippocampi. These findings do not address functionality of surviving synapses but suggest reduced granule cell inhibition in TLE is not attributable to anatomical loss of PV boutons.

Electrophysiological Signature Reveals Laminar Structure of the Porcine Hippocampus

The hippocampus is integral to working and episodic memory and is a central region of interest in diseases affecting these processes. Pig models are widely used in translational research and may provide an excellent bridge between rodents and nonhuman primates for CNS disease models because of their gyrencephalic neuroanatomy and significant white matter composition. However, the laminar structure of the pig hippocampus has not been well characterized. Therefore, we histologically characterized the dorsal hippocampus of Yucatan miniature pigs and quantified the cytoarchitecture of the hippocampal layers. We then utilized stereotaxis combined with single-unit electrophysiological mapping to precisely place multichannel laminar silicon probes into the dorsal hippocampus without the need for image guidance. We used in vivo electrophysiological recordings of simultaneous laminar field potentials and single-unit activity in multiple layers of the dorsal hippocampus to physiologically identify and quantify these layers under anesthesia. Consistent with previous reports, we found the porcine hippocampus to have the expected archicortical laminar structure, with some anatomical and histological features comparable to the rodent and others to the primate hippocampus. Importantly, we found these distinct features to be reflected in the laminar electrophysiology. This characterization, as well as our electrophysiology-based methodology targeting the porcine hippocampal lamina combined with high-channel-count silicon probes, will allow for analysis of spike-field interactions during normal and disease states in both anesthetized and future awake behaving neurophysiology in this large animal.

Rhes: a GTP-binding protein integral to striatal physiology and pathology

Rhes, the Ras Homolog Enriched in Striatum, is a GTP-binding protein whose gene was discovered during a screen for mRNAs preferentially expressed in rodent striatum. This 266 amino acid protein is intermediate in size between small Ras-like GTP-binding proteins and α-subunits of heterotrimeric G proteins. It is most closely related to another Ras-like GTP-binding protein termed Dexras1 or AGS1. Although subsequent studies have shown that the rhes gene is expressed in other brain areas in addition to striatum, the striatal expression level is relatively high, and Rhes protein is likely to play a vital role in striatal physiology and pathology. Indeed, it has recently been shown to interact with the Huntingtin protein and play a pivotal role in the selective vulnerability of striatum in Huntington's disease (HD). Not surprisingly, Rhes can interact with multiple proteins to affect striatal physiology at multiple levels. Functional studies have indicated that Rhes plays a role in signaling by striatal G protein-coupled receptors (GPCR), although the details of the mechanism remain to be determined. Rhes has been shown to bind to both α- and β-subunits of heterotrimeric G proteins and to affect signaling by both Gi/o- and Gs/olf-coupled receptors. In this context, Rhes can be classified as a member of the family of accessory proteins to GPCR signaling. With documented effects in dopamine- and opioid-mediated behaviors, an interaction with thyroid hormone systems and a role in HD pathology, Rhes is emerging as an important protein in striatal physiology and pathology.

The use of pigs in neuroscience: Modeling brain disorders

The use of pigs in neuroscience research has increased in the past decade, which has seen broader recognition of the potential of pigs as an animal for experimental modeling of human brain disorders. The volume of available background data concerning pig brain anatomy and neurochemistry has increased considerably in recent years. The pig brain, which is gyrencephalic, resembles the human brain more in anatomy, growth and development than do the brains of commonly used small laboratory animals. The size of the pig brain permits the identification of cortical and subcortical structures by imaging techniques. Furthermore, the pig is an increasingly popular laboratory animal for transgenic manipulations of neural genes. The present paper focuses on evaluating the potential for modeling symptoms, phenomena or constructs of human brain diseases in pigs, the neuropsychiatric disorders in particular. Important practical and ethical aspects of the use of pigs as an experimental animal as pertaining to relevant in vivo experimental brain techniques are reviewed. Finally, current knowledge of aspects of behavioral processes including learning and memory are reviewed so as to complete the summary of the status of pigs as a species suitable for experimental models of diverse human brain disorders.

A novel population of calretinin-positive neurons comprises reelin-positive Cajal-Retzius cells in the hippocampal formation of the adult domestic pig

Calretinin-containing neurons in the hippocampal formation, including the subiculum, presubiculum, parasubiculum, and entorhinal cortex, were visualized with immunocytochemistry. Calretinin immunoreactivity was present exclusively in non-principal cells. The largest immunoreactive cell population was found in the outer half of the molecular layer of the dentate gyrus and in the stratum lacunosum-moleculare of Ammon's horn. A proportion of these cells were also immunoreactive for reelin, a Cajal-Retzius cell marker. Similar calretinin-positive cells were found in the molecular layer of the subicular complex and entorhinal cortex. In the parasubiculum, a few immunoreactive bipolar and multipolar cells could be observed in the superficial and deep pyramidal cell layers. In the entorhinal cortex, bipolar and multipolar calretinin-positive cells were frequent in layer II, and large numbers of multipolar cells in layer V were immunoreactive. Electron microscopic analysis showed that somata of calretinin-positive cells contained either round nuclei with smooth nuclear envelopes or nuclei with multiple deep infoldings. Immunoreactive dendrites were smooth varicose, and the apposing axon terminals formed both symmetric and asymmetric synapses. Zonula adherentia were observed between calretinin-positive dendrites. Calretinin-positive axon terminals formed two types of synapses. Axon terminals with asymmetric synapses were found close to the hippocampal fissure, whereas axon terminals forming symmetric synapses innervated spiny dendrites in both the molecular layer of the dentate gyrus and in stratum lacunosum-moleculare of Ammon's horn. Calretinin-positive axon terminals formed both symmetric and asymmetric synapses with calretinin-positive dendrites. In conclusion, calretinin-positive neurons form two major subpopulations in the adult domestic pig hippocampus: (1) a gamma-aminobutyric acid (GABA)ergic subpopulation of local circuit neurons that innervates distal dendrites of principal cells in both the dentate gyrus and in Ammon's horn; and (2) Cajal-Retzius type cells close to the hippocampal fissure, as well as in the molecular layer of the subicular complex and entorhinal cortex.

Functional implications of seizure-induced neurogenesis

The neurobiological doctrine governing the concept of neurogenesis has undergone a revolution in the past few years. What was once considered dubious is now well accepted: new neurons are born in the adult brain. Science fiction is quickly becoming a reality as scientists discover ways to convert skin, bone, or blood cells into neurons. In the epilepsy arena, widespread interest has developed because of the evidence that neurogenesis increases after seizures, trauma, and other insults or injuries that alter seizure susceptibility. This review discusses some of the initial studies in this field, and their often surprising functional implications. The emphasis will be on the granule cells of hippocampus, because they are perhaps more relevant to epilepsy than other areas in which neurogenesis occurs throughout life, the olfactory bulb and subventricular zone. In particular, the following questions will be addressed: 1. Do granule cells that are born in the adult brain become functional, and what are the limits of their function? Do they behave homogeneously? Results from our own laboratory have focused on cells that become established outside the normal boundaries of the granule cell layer, forming a group of "ectopic" granule cells in the hilar region. 2. Is increased neurogenesis beneficial, or might it actually exacerbate seizures? Evidence is presented that supports the hypothesis that new granule cells may not necessarily act to ameliorate seizures, and might even contribute to them. Furthermore, cognitive deficits following seizures might in part be due to new circuits that develop between new cells and the host brain. 3. How do the new cells interact with the host brain? Several changes occur in the dentate gyrus after seizures, and increased neurogenesis is only one of many. What is the interdependence of this multitude of changes, if any? 4. Is neurogenesis increased after seizures in man? Research suggests that the data from human epileptics are actually inconsistent with the studies in animal models of epilepsy, because there is little evidence of increased neurogenesis in epileptic tissue resected from intractable epileptics. Yet neurogenesis has been shown to occur in humans throughout adult life. What might be the reasons for these seemingly disparate results?

Preservation of perisomatic inhibitory input of granule cells in the epileptic human dentate gyrus

Temporal lobe epilepsy is known to be associated with hyperactivity that is likely to be generated or amplified in the hippocampal formation. The majority of granule cells, the principal cells of the dentate gyrus, are found to be resistant to damage in epilepsy, and may serve as generators of seizures if their inhibition is impaired. Therefore, the parvalbumin-containing subset of interneurons, known to provide the most powerful inhibitory input to granule cell somata and axon initial segments, were examined in human control and epileptic dentate gyrus. A strong reduction in the number of parvalbumin-containing cells was found in the epileptic samples especially in the hilar region, although in some patches of the granule cell layer parvalbumin-positive terminals that form vertical clusters characteristic of axo-axonic cells were more numerous than in controls. Analysis of the postsynaptic target elements of parvalbumin-positive axon terminals showed that they form symmetric synapses with somata, dendrites, axon initial segments and spines as in the control, but the ratio of axon initial segment synapses was increased in the epileptic tissue (control: 15.9%, epileptic: 31.3%). Furthermore, the synaptic coverage of granule cell axon initial segments increased more than three times (control: 0.52, epileptic: 2.10 microm synaptic length/100 microm axon initial segment membrane) in the epileptic samples, whereas the amount of somatic symmetric synapses did not change significantly. Although the number of parvalbumin-positive interneurons is decreased, the perisomatic inhibitory input of dentate granule cells is preserved in temporal lobe epilepsy. Basket and axo-axonic cell terminals - whether positive or negative for parvalbumin - are present, moreover, the axon collaterals targeting axon initial segments sprout in the epileptic dentate gyrus. We suggest that perisomatic inhibitory interneurons survive in epilepsy, but their somadendritic compartment and partly the axon loses parvalbumin or immunoreactivity for parvalbumin. The hyperinnervation of axon initial segments might be a compensatory change in the inhibitory network, but at the same time may lead to a more effective synchronization of granule cell firing that could contribute to the generation or amplification of epileptic seizures.

Hippocampal fields in the hedgehog tenrec. Their architecture and major intrinsic connections

The Madagascan lesser hedgehog tenrec was investigated to get insight into the areal evolution of the hippocampal formation in mammals with poorly differentiated brains. The hippocampal subdivisions were analyzed using cyto- and chemoarchitectural criteria; long associational and commissural connections were demonstrated with tracer techniques. The hedgehog tenrec shows a well differentiated dentate gyrus, CA3 and CA1. Their major intrinsic connections lie within the band of variations known from other species. The dentate hilar region shows calretinin-positive mossy cells with extensive projections to the molecular layer. The calbindin- and enkephalin-positive granule mossy fibers form a distinct endbulb and do not invade the CA1 as reported in the erinaceous hedgehog. Isolated granule cells with basal dendrites were also noted. A CA2 region is hard to identify architecturally; its presence is suggested due to its contralateral connections. Subicular and perisubicular regions are clearly present along the dorsal aspects of the hemisphere, but we failed to identify them unequivocally along the caudal and ventral tip of the hippocampus. A temporal portion of the subiculum, if present, differs in its chemoarchitecture from its dorsal counterpart. The perisubicular region, located medially adjacent to the dorsal subiculum may be equivalent to the rat's presubiculum; evidence for the presence of a parasubiculum was rather weak.

Acute hypoxia-induced alterations of calbindin-D28k immunoreactivity in cerebellar Purkinje cells of the guinea pig fetus at term

Purkinje cells (PCs) are vulnerable to hypoxic/ischemic insults and rich in calcium and calcium-buffering/sequestering systems, including calcium-binding proteins (CaBPs). Calbindin-D28k is an EF-hand CaBP, which is highly expressed in PCs where it acts primarily as a cellular Ca++ buffer. Elevation of [Ca++] in the cytosol and nuclei of PCs is pivotal in hypoxic/ischemic cell death. We hypothesize that hypoxia results in decreased concentration, or availability of calbindin-D28k in PCs, thereby decreasing their buffering capacity and resulting in increase of intracellular and intranuclear [Ca++]. Cerebellar tissues from normoxic fetuses were compared to fetuses obtained from term pregnant guinea pigs exposed to hypoxia [7% FiO2] for 60 min. The pregnant guinea pigs were either killed upon delivery immediately following hypoxia (Hx0h) or were subsequently allowed to recover for 24 h (Hx24h) or 72 h (Hx72h). Fetal brain hypoxia was documented biochemically by a decrease in brain tissue levels of ATP and phosphocreatine. Compared to normoxic fetuses, there is a predominantly somatodendritic loss or decrease of calbindin-D28k immunohistochemical staining in PCs of Hx0h (p < 0.005), Hx24h (p < 0.05), and Hx72h (p < 0.005) fetuses. Hypoxia-induced alterations of calbindin-D28k immunoreactivity are qualitatively similar at all time points and include a distinctive intranuclear localization in subpopulations of PCs. A similar trend is demonstrated by immunoblotting. Subpopulations of TUNEL+/calbindin-D28k- PCs lacking morphologic features of apoptosis or necrosis are demonstrated in Hx24h and Hx72h fetuses. The present study demonstrates an abrogating effect of perinatal hypoxia on calbindin-D28k immunoreactivity in cerebellar PCs. The perturbation of this Ca++ buffer protein in hypoxia-induced neuronal injury may herald delayed cell death or degeneration.

Determination of stereotaxic coordinates for the hippocampus in the domestic pig

In this study a stereotaxic instrument and a stereotaxic procedure based on external skull structures, to be used in prepubertal male Landrace pigs weighing less than 30 kg, is described. The instrument represents an adaptation of the apparatus designed by Marcilloux et al., Brain Res Bull 1989;22:591-597, but we have modified the instrument for stereotaxic procedures based on external skull structures, instead of intracerebral structures necessitating ventriculography (Marcilloux et al., Brain Res Bull 1989;22:591-597). For this reason the U-shaped frame and the ear-bar supports have been changed allowing the three-dimensional placement of the ear-bars into the oblique auditory canals. Firm fixation of the skulls of pigs weighing less than 30 kg, was furthermore secured with modified infraorbital ridges and hard palate pieces. Measurements of distances between external skull structures in animals of the same sex, age and weight showed a negligible variation, thus enabling definition of the horizontal, frontal and sagittal zero planes using external skull structures alone. Stereotaxic coordinates for the hippocampal region of male Landrace pigs weighing 10 kg were then provided and the coordinates from two different levels of the hippocampal region are presented in the text. The reliability of the stereotaxic instrument was finally secured by intrahippocampal injections of ink at predetermined coordinates.

Levels of stimulatory G protein are increased in the rat striatum after neonatal lesion of dopamine neurons

After neonatal lesions of dopamine neurones, an enhanced behavioural responsiveness towards D1 agonists has been described, suggesting a D1 receptor hypersensitivity. In the present study, unilateral striatal dopamine denervation in newborn rats induced a pronounced rotational behaviour following apomorphine injection at the adult age, without any change in the density of D1 binding sites in the denervated striatum. The amount of stimulatory G(olf) alpha subunit was increased by 35% in the lesioned striatum. The large form and the short forms of Gs alpha were also increased by 26% and 9%, respectively. Since in striatal neurones, the coupling of D1 receptor to adenylate cyclase is mostly provided by G(olf) alpha, our results strongly suggest that D1 hypersensitivity described after neonatal dopamine lesions results from an increase in the levels of G(olf) alpha protein.

Age-related loss of calcium binding proteins in rabbit hippocampus

Using immunocytochemistry hippocampal levels of the calcium binding proteins calbindin 28K (CB) and parvalbumin (PV) was studied in young (1 month) to very old (60 month) Albino rabbits. Young (3 month) and senescent (30 month) Wistar rats were also examined to compare the distribution and age dependency of PV and CB in both species. The distribution of PV-ir is similar in the rabbit and rat hippocampus. Aging in both species yielded a small loss of PV-ir in axon terminals. The presence of CB-ir interneurons throughout the hippocampus, and the heavy investment of the dentate gyrus (DG) granular cells with CB-ir was also similar in both species. In rabbits, the number of CB-ir interneurons in the CA1, as well as the density of CB-ir in the DG decreased in the first year of life, and did not change between 12-48 months of age. A secondary reduction in the density of CB-ir in the DG was observed at ages beyond 48 months. A similar loss of CB-ir in the DG occurred in the rat. In the CA1, however, the density of CB-ir was similar in young and aged rats. Another remarkable finding was the total absence of CB-ir in CA1 pyramidal neurons of rabbits at any age. Thus, the distribution and age dependency of PV-ir in the hippocampus is similar in both species. The decline of CB-ir in the DG with advancing age is very prominent and may be related to an altered calcium homeostasis in these cells. However, the absence of CB-ir in the CA1 of rabbits makes a causal role for CB in the functional decline of CA1 pyramidal cells during aging unlikely.

Distribution of the calcium binding proteins, calbindin D-28K and parvalbumin, in the subicular complex of the adult mouse

The immunohistochemical localizations of two specific calcium binding proteins, calbindin D-28K (calbindin) and parvalbumin (PV) were examined in the subicular complex, that is, the subiculum, presubiculum, and parasubiculum, of the adult mouse and were compared in detail with staining pattern of the acetylcholinesterase (AChE) histochemistry. The calbindin immunoreactivity exhibited a conspicuous regional and laminar pattern of distribution, which somewhat resembled the AChE staining pattern but was apparently different from the latter in various points. The PV immunoreactivity also exhibited a characteristic regional difference, although less prominent. The subiculum could be divided into two subregions, intensely calbindin-immunoreactive (calbindin-IR) and AChE stained proximal subiculum and only faintly calbindin-IR and AChE stained distal subiculum. In the subiculum most of calbindin-IR neurons were pyramidal cells which were clustered in the superficial half of the cell layer in the proximal subiculum and appeared to be segregated from calbindin negative pyramidal cells located in the distal subiculum and in the basal part of the proximal subiculum. In the presubiculum calbindin-IR neurons were clustered in layer 2, most of which were supposed to be presubicular pyramidal cells. In the parasubiculum, the overall immunostaining pattern of PV and calbindin were somewhat complementary. In the transition area calbindin-IR neurons were clustered but few PV-IR neurons were located, and thus the distribution of immunoreactive neuronal somata was apparently different from the adjacent parts of the parasubiculum, indicating that the transition area might be a separate entity. In addition to calbindin-IR presumable principal neurons, calbindin-IR and PV-IR nonpyramidal cells were scattered throughout the subicular complex. Furthermore, these two calcium binding proteins were colocalized in some nonpyramidal cells in the subicular complex. The present study revealed some new aspects of the areal and laminar organization of the subicular complex, which had not been shown by previous classical purely morphological approaches.

Hippocampus of the domestic pig: a stereological study of subdivisional volumes and neuron numbers

With the aim of establishing a quantitative structural basis for comparative and experimental studies, the volumes of the hippocampal subdivisions and the total number of neurons in each subdivision were estimated in domestic pig brains using modern stereological techniques. In addition to a detailed description of the stereological methods used in the analysis, comprehensive descriptions of the architectonic boundaries of the subdivisions are included. The absolute and relative volumes of the subdivisions were compared to those of a number of other species and the relationship between the number of neurons and the volume of the subdivisions was compared to that in homologous subdivisions of laboratory rats and humans. The methodology used to estimate the volumes and the total number of neurons in the individual subdivisions were evaluated with regard to the sensitivity that they can provide in experimental studies.

Cholecystokinin-, enkephalin-, and substance P-like immunoreactivity in the dentate area, hippocampus, and subiculum of the domestic pig

The distribution of cholecystokinin-like, enkephalin-like, and substance P-like immunoreactivities is described in the dentate area, hippocampus, and subiculum of the domestic pig (Sus scrofa domesticus) as a baseline for future experimental studies. The distributions in the pig are compared with previous observations in other species. Cholecystokinin-like immunoreactive nerve cell bodies were intensely stained and present in large numbers in all subfields studied. Cholecystokinin-like immunoreactive terminals appeared as stained puncta, whereas fibers were only rarely encountered. The puncta were mainly seen in the dentate molecular layer and dentate granule cell layer, the pyramidal cell layer of the hippocampal regio inferior, stratum moleculare of the hippocampal regio superior, and in the subiculum. Enkephalin-like immunoreactive nerve cell bodies were faintly stained and generally present in very small numbers, except for some pyramidal cells in the subicular cell layer. Enkephalin-like immunoreactive fibers were few in number, whereas stained puncta appeared with variable densities. Puncta of particularly high densities were found in the dentate molecular layer, whereas they appeared of moderate density in the dentate hilus, stratum moleculare of the hippocampal regio superior, and in the subiculum. Substance P-like immunoreactive nerve cell bodies were few and very faintly stained. They primarily occurred in the dentate hilus, stratum oriens of the hippocampus, and in the subicular cell layer. Stained fibers were few in number, whereas stained puncta were present in abundant numbers corresponding to the mossy fiber projection in the dentate hilus and the layer of mossy fibers of the hippocampal regio inferior, and in moderate numbers in stratum moleculare of the hippocampal regio superior and in the subiculum. For all three neuropeptides there were consistent and very characteristic variations in the distribution of immunoreactivity along the septotemporal axis of the hippocampus. When viewed in a comparative perspective the distribution of enkephalin-like and substance P-like terminals in the domestic pig displayed striking differences from the basic pattern observed in other species. This contrasted with the distribution of cholecystokinin-like neurons and terminals, which resembled more closely these species.

Somatostatin- and neuropeptide Y-like immunoreactivity in the dentate area, hippocampus, and subiculum of the domestic pig

With the principal aim of providing baseline observations for future experimental studies, the distribution of somatostatin-like and neuropeptide Y-like immunoreactivities is described in the dentate area, hippocampus, and subiculum of the domestic pig (Sus scrofa domesticus) and compared with the distribution described in other mammals. Intensely stained somatostatin-like immunoreactive nerve cell bodies were present throughout the region, with highest densities in the dentate hilus, stratum radiatum and stratum oriens of the hippocampal regio inferior, stratum oriens of the hippocampal regio superior, and in the subicular cell layer. Somatostatin-like immunoreactive terminals were represented by both stained fibers and stained puncta. Scattered somatostatin-like immunoreactive nerve fibers were seen in most areas, but regular fiber plexuses were present in the dentate molecular layer and dentate hilus, stratum moleculare of the hippocampus, and in the subicular plexiform layer. Somatostatin-like immunoreactive puncta were seen in the dentate molecular layer, stratum moleculare of the hippocampus, and in the subicular plexiform layer. Neuropeptide Y-like immunoreactive nerve cell bodies were less numerous than somatostatin-like immunoreactive ones. They were mainly seen in the dentate granule cell layer and dentate hilus, stratum radiatum and stratum oriens of the hippocampus, and in the subicular cell layer. Intensely stained neuropeptide Y-like immunoreactive fibers were numerous, and present in all areas examined. They formed fiber plexuses in the dentate molecular layer and dentate hilus, stratum moleculare of the hippocampal regio superior, and in the subicular plexiform layer. Neuropeptide Y-like immunoreactive puncta were present in the dentate molecular layer, stratum moleculare of the hippocampus, and in the subicular plexiform layer. Consistent and very characteristic variation in the distribution of somatostatin-like and neuropeptide Y-like immunoreactivity was found along the septotemporal axis of the hippocampus. The distribution of somatostatin-like and neuropeptide Y-like neurons and terminals in the domestic pig displayed striking similarities with the basic pattern of organization of these neuropeptides in other species, although more subtle species-specific characteristics were also observed in the pig.

Histochemical demonstration of zinc in the hippocampal region of the domestic pig: III. The dentate area

The distribution of zinc was described in the dentate area, a part of the hippocampal region, of the domestic pig. A modification of Timm's sulphide silver procedure, the Neo-Timm method, was used for the histochemical demonstration of zinc. The staining of the dentate area exhibited a well-defined stratified pattern, the predominant part of the staining being restricted to the neuropil, although weakly stained nerve cell bodies were observed in the hilus fasciae dentatae. In the molecular layer, three distinct sublaminae were seen at most septotemporal levels. The outer and inner sublaminae displayed medium staining intensity, whereas the intermediate sublamina appeared extremely pale. The granular cell layer was well stained in its superficial two thirds, because of dense masses of staining occupying the interstices between the unstained granular cells. In the hilus fasciae dentatae, extreme differences in staining intensity were seen between the layers, ranging from very intense staining of the outer hilar cell layer to generally weak staining of the inner plexiform layer. The distribution of zinc in the pig was compared with that in the guinea pig and rat, described previously. The staining pattern of the molecular layer showed striking species differences, whereas the granular cell layer appeared very near identical. The stratified staining pattern seen in the hilus of the pig is very similar to the distribution observed in the guinea pig, but differs from the essentially homogeneous staining of the rat hilus.(ABSTRACT TRUNCATED AT 250 WORDS)

Histochemical demonstration of zinc in the hippocampal region of the domestic pig: II. Subiculum and hippocampus

The distribution of zinc has been described in two areas of the hippocampal region of the domestic pig, viz., the subiculum and the hippocampus. Zinc was demonstrated histochemically according to the Neo-Timm method, a modification of the sulphide-silver procedure. In each of the examined areas the staining displayed a distinctly stratified pattern which has been compared in detail to fields and layers defined on the basis of cyto- and fibroarchitecture, resulting in a combined chemo- and cytoarchitectonic map. Most of the staining was confined to the neuropil, but a considerable number of stained nerve cell bodies were seen in both the subiculum and the hippocampus. In the subiculum, the plexiform layer was divided into a superficial, weakly stained subzone and a deep, better stained subzone. The cell layer was generally well stained, but displayed a complex staining pattern with differences in staining intensity of both the cell bodies and neuropil. In regio superior of the hippocampus, the stratum moleculare appeared weakly stained, with the exception of a tapering process of more darkly stained tissue projecting from the plexiform layer of the subiculum into the deepest part of the layer. Stratum radiatum and the superficial subzone of stratum oriens showed a weak staining intensity, contrasting to the relatively darkly stained pyramidal cell layer and the intensely stained deep subzone of stratum oriens. In regio inferior, the stratum moleculare was divided into a moderately stained superficial part and an unstained deep part. Stratum radiatum and stratum oriens both appeared weakly stained. The layer of mossy fibers was very intensely stained and appeared almost homogeneously black in its main suprapyramidal part, whereas the infrapyramidal part was looser in character. The pyramidal cell layer was darker than in regio superior. The distribution of zinc in the pig was compared with that in the guinea pig and rat, described previously. The staining pattern is fundamentally similar in all three species, though notable species-specific traits do exist.