Genetic loci affecting bone structure and strength in inbred COP and DA rats

Previous studies have shown that the Copenhagen 2331 (COP) and Dark Agouti (DA) rats have significant differences in bone structure and strength despite their similar body mass. Thus, these inbred rat strains may provide a unique resource to identify the genetics underlying the phenotypic variation in bone fragility. A sample of 828 (405 males and 423 females) COPxDA F2 progeny had extensive phenotyping for bone structure measures including cortical bone area and polar moment of inertia at the femur midshaft and total, cortical and trabecular bone areas, for the lumbar vertebra 5 (L5). Bone strength phenotypes included ultimate force, stiffness and work to failure of femur and L5. These skeletal phenotypes were measured using peripheral quantitative computed tomography (pQCT) and mechanical testing. A whole-genome screen was conducted in the F2 rats, using microsatellite markers spaced at approximately 20 cM intervals. Genetic marker maps were generated from the F2 data and used for genome-wide linkage analyses to detect linkage to the bone structure and strength phenotypes. Permutation testing was employed to obtain the thresholds for genome-wide significance (p<0.01). Significant QTL for femur structure and strength were identified on chromosome (Chr) 1 with a maximum LOD score of 33.5; evidence of linkage was found in both the male and female rats. In addition, Chrs 6, 7, 10, 13, 15 and 18 were linked to femur midshaft structure. QTL linked to femur strength were identified on Chrs 5 and 10. For L5 vertebrae, Chrs 2, 16, and 18 harbored QTL for cortical structure and trabecular structure for L5 was linked to Chrs 1, 7, 12, and 18. One female-specific QTL for femur ultimate force was identified on Chr 5, and two male-specific QTL for L5 cortical area were found on Chrs 2 and 18. Our study demonstrates strong evidence of linkage for bone structure and strength to multiple rat chromosomes.

Strain Differences in the Branching of the Sciatic Nerve in Rats

The sciatic nerve in the rat is the site most often used for peripheral nerve regeneration studies. The length of sciatic nerve available for research, however, depends on the point at which the sciatic nerve divides into the peroneal and tibial nerves. In the present study, the hind limbs of 150 adult male rats of five different strains (Sprague-Dawley, Fischer 344, Wistar-Han, Lewis and Nude) were analysed with regard to femur length, the point at which the sciatic nerve divides into the tibial and peroneal nerves, and where these are surrounded by the same epineurium, and the point at which they are encased in individual epineurial sheaths. The results indicate that the lengths of sciatic nerve are fairly constant in all strains of rats. In absolute terms, they amount to about one-third of the length of the femur for stretches of undivided sciatic nerve, and up to nearly half of the femur length for stretches where the tibial and peroneal nerves are already present, but are still enclosed by the same epineurium. In 61.7% of the hind limbs examined in Fischer rats, however, no sciatic nerve could be seen as such, but only in the form of its successors surrounded by the separate epineuria. This makes it highly advisable not to use male adult Fischer rats in peripheral nerve regeneration studies with the sciatic nerve as the point of focus.

Rodent models of prefrontal cortical function

In this article, we consider whether studies in rats can provide useful information regarding the debate about the functions of the primate prefrontal cortex. At a superficial level, comparison of regional specializations within the prefrontal cortices of different species suggests functional correspondence. Unfortunately, the nature of functional specialization in primate prefrontal cortex is controversial, and data supporting the idea of homology between specific areas of rat and primate prefrontal cortex are weak. Nevertheless, we argue here that studies of the computational functions within the relatively undifferentiated prefrontal cortex of rats can shed light on processing in primate prefrontal cortex.

Neurodegeneration and glial activation patterns after mechanical nerve injury are differentially regulated by non-MHC genes in congenic inbred rat strains

Ventral root avulsion in the rat leads to a retrograde response, with activation of glia and up-regulation of immunologic cell surface molecules such as major histocompatibility complex (MHC) antigens, and the subsequent degeneration of a large proportion of the lesioned motoneurons. Herein, we examined several inbred congenic rat strains previously known to react differently to experimentally induced autoimmune diseases and demonstrate a substantial genetic diversity in the regulation of glial activation and neuron death in this injury model. The panel of examined inbred rat strains included DA(RT1AV1), PVG.1AV1, LEW.1AV1, LEW.1N, BN(RT1N) and E3(RT1U), and the following parameters were determined: (1) MHC class II expression on glia; (2) expression of glial fibrillary acidic protein, C3 complement, and microglial response factor-1 mRNAs in glia; (3) levels of the tumor necrosis factor-alpha and interleukin-1beta cytokine mRNAs; (4) degree of motoneuron loss. The findings of considerable strain-dependent differences in all parameters studied demonstrate important polymorphisms in the genetic regulation of these events. Furthermore, some of the studied features segregated from each other, suggesting independent regulatory mechanisms. Genes outside of the MHC complex are mainly implicated as being of importance for the phenotypic differences, as significant differences were recorded between the MHC congenic strains differing in the non-MHC genes but not vice versa. These results contribute new important insights into the genetic regulation of glial reactivity and neuron death after mechanical nerve injuries. In addition, the finding of conspicuous strain-dependent differences makes it necessary to consider the genetic background when designing and interpreting animal experiments involving noxious insults to the central nervous system resulting in glial activation and nerve cell loss.

Lens and retinal changes in the WBN/Kob rat (spontaneously diabetic strain). Electron-microscopic study

Male WBN/Kob rats represent a spontaneously diabetic strain with hyperglycemia, cataracts, nephropathy, neurophathy, pancreatic fibrosis and hyperlipemia. Cataracts and retinal changes in WBN/Kob rats were examined by light and electron microscopy to evaluate the ocular complications. Lens opacity was present in the posterior subcapsular and center of the anterior cortex of male 14-month-old WBN/Kob rats. Light and transmission electron microscopy showed swelling and irregularity of lens fibers. Scanning electron microscopy revealed that lens fibers were irregular and had many granules and bulging processes of various sizes on the cortical side of the opacified region. The nuclear side of the opacified region showed spongy changes and complete absence of lens fibers. Electron microscopy showed retinal degeneration in the photoreceptor outer segments of 1-month-old male WBN/Kob rats. Light microscopy showed thin outer segments and outer nuclear layers in 5-month-old rats, and electron microscopy revealed severe degeneration in the outer segments. The retinas of 11-month-old rats were thinner; the outer plexiform layer was very thin; the photoreceptor cell nuclei in the outer nuclear layer had decreased to one layer and were almost in contact with the inner nuclear layer nuclei, while the visual cells had disappeared. Retinal degeneration had progressed even further in 14-month-old rats, and very few photoreceptor cell nuclei remained. The retinal capillary lumens were small, and their pericytes had thickened basement membranes. The basement membranes of retinal capillaries from WBN/Kob rats were significantly thicker than those from control Wistar rats (p < 0.0001). Although this rat has spontaneous diabetic features, such as cataracts, its retinal changes look more degenerative.

Long-term infusion of kallikrein attenuates renal injury in Dahl salt-sensitive rats

We investigated whether long-term infusion of kallikrein would attenuate renal injury in salt-induced hypertension in Dahl salt-sensitive (Dahl S) rats. A subdepressor dose of purified rat urinary kallikrein (RUK) (700 ng/day) was infused intravenously by an osmotic minipump for 4 weeks in male Dahl S rats fed a high-salt (2% NaCl) diet. This dose did not affect the time-dependent elevation of blood pressure. However, urinary protein excretion was significantly decreased, and the glomerular filtration rate was increased. These beneficial effects were reflected morphologically by an attenuation of the glomerulosclerotic lesions and tubular injury seen in the hypertensive Dahl S rats. The kallikrein infusion increased the urinary excretion of bradykinin and stimulated the excretion of cyclic GMP, suggesting that the kallikrein-kinin-prostaglandin and nitric oxide axes were enhanced by the RUK infusion. The alterations induced by such infusion were potentiated by the concomitant administration of the angiotensin converting enzyme inhibitor alacepril. These studies indicated that long-term replacement with rat tissue kallikrein attenuates renal injury in hypertensive Dahl S rats, and this is probably mediated by an enhanced function of the kallikrein-kinin-prostaglandin and nitric oxide systems.

The implication of renin-angiotensin system on renal injury seen in Dahl salt-sensitive rats

Angiotensin II (Ang II) progresses to remodeling of the cardiovascular system through nonhemodynamic as well as hemodynamic effects. There have been few data in vivo on whether subpressor concentration of Ang II is exerted to injure directly the cardiovascular system in hypertension. To test this hypothesis, we investigated, using Dahl salt-sensitive (Dahl S) rats, whether subpressor dose of Ang II progresses to cardiovascular injury observed in salt-induced hypertension. Recent studies have provided evidence that renin-angiotensin inhibition protects against renovascular injury in human hypertension as well as in experimental animals. Particularly in the case of Dahl salt-sensitive rats, a genetic model of volume-dependent hypertension in humans, they are likely to develop more severe arterial and renal injuries than those seen in spontaneously hypertensive rats with similar blood pressure levels. The mechanism of the susceptibility to hypertensive injuries is uncertain; however, renin-angiotensin inhibition significantly improved morphologic and functional injuries in the kidney of Dahl S rats. Conversely, subpressor dose of Ang II infusion exacerbated renal function and progressed to glomerulosclerotic lesions. Alterations of Ang II concentration in physiologic range influenced morphologic and functional injuries in Dahl S rats. Multivariate analysis revealed that activity of the renin-angiotensin system is an independent risk factor to glomerular injury in salt-induced hypertension. These data are in favor of the therapeutic strategy in human hypertension that inhibition of renin-angiotensin system is of value to produce beneficial effects of blood pressure reduction on organ injuries.

Comparison of projection neurons in the pontine nuclei and the nucleus reticularis tegmenti pontis of the rat

Dendritic features of identified projection neurons in two precerebellar nuclei, the pontine nuclei (PN) and the nucleus reticularis tegmenti pontis (NRTP) were established by using a combination of retrograde tracing (injection of fluorogold or rhodamine labelled latex micro-spheres into the cerebellum) with subsequent intracellular filling (lucifer yellow) in fixed slices of pontine brainstem. A multivariate analysis revealed that parameters selected to characterize the dendritic tree such as size of dendritic field, number of branching points, and length of terminal dendrites did not deviate significantly between different regions of the PN and the NRTP. On the other hand, projection neurons in ventral regions of the PN were characterized by an irregular coverage of their distal dendrites by appendages while those in the dorsal PN and the NRTP were virtually devoid of them. The NRTP, dorsal, and medial PN tended to display larger somata and more primary dendrites than ventral regions of the PN. These differences, however, do not allow the differentiation of projection neurons within the PN from those in the NRTP. They rather reflect a dorso-ventral gradient ignoring the border between the nuclei. Accordingly, a cluster analysis did not differentiate distinct types of projection neurons within the total sample. In both nuclei, multiple linear regression analysis revealed that the size of dendritic fields was strongly correlated with the length of terminal dendrites while it did not depend on other parameters of the dendritic field. Thus, larger dendritic fields seem not to be accompanied by a higher complexity but rather may be used to extend the reach of a projection neuron within the arrangement of afferent terminals. We suggest that these similarities within dendritic properties in PN and NRTP projection neurons reflect similar processing of afferent information in both precerebellar nuclei.

Efferent connections of the caudal part of the globus pallidus in the rat

The efferent connections of the caudal pole of the globus pallidus (GP) were examined in the rat by employing the anterograde axonal transport of Phaseolus vulgaris leucoagglutinin (PHA-L), and the retrograde transport of fluorescent tracers combined with choline acetyltransferase (ChAT) or parvalbumin (PV) immunofluorescence histochemistry. Labeled fibers from the caudal GP distribute to the caudate-putamen, nucleus of the ansa lenticularis, reuniens, reticular thalamic nucleus (mainly its posterior extent), and along a thin strip of the zona incerta adjacent to the cerebral peduncle. The entopeduncular and subthalamic nuclei do not appear to receive input from the caudal GP. Descending fibers from the caudal GP course in the cerebral peduncle and project to posterior thalamic nuclei (the subparafascicular and suprageniculate nuclei, medial division of the medial geniculate nucleus, and posterior intralaminar nucleus/peripeduncular area) and to extensive brainstem territories, including the pars lateralis of the substantia nigra, lateral terminal nucleus of the accessory optic system, nucleus of the brachium of the inferior colliculus, nucleus sagulum, external cortical nucleus of the inferior colliculus, cuneiform nucleus, and periaqueductal gray. In cases with deposits of PHA-L in the ventral part of the caudal GP, labeled fibers in addition distribute to the lateral amygdaloid nucleus, amygdalostriatal transition area, cerebral cortex (mainly perirhinal, temporal, and somatosensory areas) and rostroventral part of the lateral hypothalamus. Following injections of fluorescent tracer centered in the lateral hypothalamus, posterior intralaminar nucleus, substantia nigra, pars lateralis, or lateral terminal nucleus, a substantial number of retrogradely labeled cells is observed in the caudal GP. None of these cells express ChAT immunoreactivity, but, except for the ones projecting to the lateral hypothalamus, a significant proportion is immunoreactive to PV. Our results indicate that caudal GP efferents differ from those of the rostral GP in that they project to extensive brainstem territories and appear to be less intimately related to intrinsic basal ganglia circuits. Moreover, our data suggest a possible participation of the caudal GP in feedback loops involving posterior cortical areas, posterior striatopallidal districts, and posterior thalamic nuclei. Taken as a whole, the projections of the caudal GP suggest a potential role of this pallidal district in visuomotor and auditory processes.

Hemodynamic and biochemical characteristics of the aorta in the WKY, SHR, WKHT, and WKHA rat strains

This study was designed to characterize the hemodynamic and biochemical properties of the abdominal aorta in four genetically related inbred rat strains that express genetic hypertension and hyperactive behavior in varying combinations. These include (1) the spontaneously hypertensive rat (SHR), which is hypertensive, hyperactive, and hyperreactive to stress; (2) Wistar-Kyoto (WKY) rats, which express none of these traits; (3) WKHT rats, which are hypertensive but not hyperactive; and (4) WKHA rats, which are hyperactive and hyperreactive to stress, but normotensive. Together, these four strains allowed us to examine the structural and functional changes in the aorta in the hypertensive SHR, the most widely used animal model of genetic hypertension, while controlling for the variables of hyperactivity and hyperreactivity that are also expressed in the SHR. Four groups of animals of both sexes were studied: (1) WKY, n = 101, (2) WKHA, n = 33, (3) WKHT, n = 91, and (4) SHR, n = 28. Blood pressure (BP) was determined by tail plethysmography as well as direct intraarterial monitoring under anesthesia. Fixed specimens were prepared for histologic analysis and the wall thickness determined morphometrically. Quantification of soluble tissue protein, elastin, and collagen in the aortic tissue was determined by measuring leucine (leu), hydroxyproline (HP/leu), and desmosine (DES/leu). The hypertensive strains (SHR and WKHT) had significantly higher tail BP than the normotensive strains (WKY and WKHA)-WKY: 128.7 +/- 22.3; WKHA: 126.7 +/- 14.6; WKHT: 162.8 +/- 21.2; SHR: 164.2 +/- 36.1 (p < 0.0001). Additionally, intraaortic diastolic BP and mean BP were higher in SHR rats than in WKHT. Morphometric studies showed the media thickness in the SHR rats was significantly greater than in the WKY and WKHA rats and no different than in the WKHT rats. Significantly less of the aortic wall protein was present as elastin in the hypertensive rats (SHR and WKHT), as well as the hyperactive rats (WKHA), compared to rats that had neither trait (WKY). These studies provide new information regarding aortic structure and function in genetic hypertension using inbred strains to control for the hyperactivity/hyperreactivity traits that coexist with hypertension in the SHR. They reveal that hypertensive aortas have altered matrix proteins that cannot be explained simply on the basis of blood pressure alone.

Localisation of endothelin-1 in rat aortae, the relationship to flow and elastic tissue tears

The aortic expression of endothelin-1 (ET-1) was examined in three species of rat using a novel en face immunohistochemical technique. A genetically hypertensive strain was compared to two normotensive strains, one of which is known to develop spontaneous lesions within the abdominal aorta. ET-1-positive staining was increased about the major aortic branch ostia and over the dorsal abdominal aortic wall in all three species indicating a flow-related expression pattern. Mitotic and hyperchromatic endothelial cells stained strongly for ET-1 as did occasional multi-nucleated endothelial cells. The aortic-lesion-prone normotensive strain developed transverse tears of the internal elastic lamina with a corresponding endothelial cell response. Endothelium at the edge of these lesions was strongly stained for ET-1 and appeared to be associated with increased leucocyte adhesion as did other strongly ET-1-stained areas in all three species. This study indicates that increased ET-1 expression is anatomically localised within the rat aorta, possibly by haemodynamic stress. This may have implications for maintaining endothelial cell confluence, aortic smooth muscle cell reparative processes and possibly eventual pathophysiological conditions such as atherosclerosis.

Ultrastructural study of the granule cell domain of the cochlear nucleus in rats: mossy fiber endings and their targets

The principal projection neurons of the cochlear nucleus receive the bulk of their input from the auditory nerve. These projection neurons reside in the core of the nucleus and are surrounded by an external shell, which is called the granule cell domain. Interneurons of the cochlear granule cell domain are the target for nonprimary auditory inputs, including projections from the superior olivary complex, inferior colliculus, and auditory cortex. The granule cell domain also receives projections from the cuneate and trigeminal nuclei, which are first-order nuclei of the somatosensory system. The cellular targets of the nonprimary projections are mostly unknown due to a lack of information regarding postsynaptic profiles in the granule cell areas. In the present paper, we examined the synaptic relationships between a heterogeneous class of large synaptic terminals called mossy fibers and their targets within subdivisions of the granule cell domain known as the lamina and superficial layer. By using light and electron microscopic methods in these subdivisions, we provide evidence for three different neuron classes that receive input from the mossy fibers: granule cells, unipolar brush cells, and a previously undescribed class called chestnut cells. The distinct synaptic relations between mossy fibers and members of each neuron class further imply fundamentally separate roles for processing acoustic signals.

[Age-related changes in the retina of WBN/Kob rats--a pathological study]

Male rats of the WBN/Kob strain, which are known to spontaneously develop diabetes with aging, were examined for histopathological changes in the retina. Five rats (10 eyes) each of WBN/Kob and Wistar/ST as a control were used, and the thickness of the retinal layers, both the central region and the peripheral region of the retina, were measured on weeks 1, 2, 3, 5, 9, 13, 17, 23, 27, 36, 45, 54, 67 and 80 after birth. The rod and cone cell layer in WBN/Kob rats was under-grown, and its thickness decreased 71.7% in the central zone and 59.3% in the peripheral zone of the retina compared with that of the control. In the central and peripheral retina, the rod and cone cell layer, outer nuclear layer and outer plexiform layer, as well as the inner plexiform layer in the central retina, gradually decreased in thickness from 5-45 weeks of age. In the central and peripheral parts of the retina, the number of nuclei decreased in accordance with the thinning of the nuclear layer. The thinned layers showed only cell loss. The rod and cone cell layer of the peripheral retina was thinner than that of the central retina. We obtained the following findings in the retina of male WBN/Kob rats. First, the rod and cone cell layer is undergrown compared with that of the control. Second, the first change occurred in the rod and cone cell layer. Third, the thinning of the rod and cone cell layer appeared at 5 weeks of age, and thinning with aging was slow. And finally, the thinning of the peripheral retina was more severe than that of the central retina. From the above findings, it seems that retinal changes in WBN/Kob rats are similar to the retinal degeneration of rds mice (retinal degeneration slow mice) and that WBN/Kob rats provide a useful animal model for human retinopathy.

Iron and copper metabolism in analbuminaemic rats fed a high-iron diet

The metabolism of iron and copper in male Nagase analbuminaemic (NA) and Sprague Dawley (SD) rats was compared. Relative liver weight was higher and spleen weight significantly lower in NA than SD rats. In NA rats, red blood cell count, haemoglobin and haematocrit were lower, whereas plasma transferrin, total iron-binding capacity and mean corpuscular haemoglobin were higher when compared with SD rats. Iron concentrations in plasma, liver, kidneys and heart were higher, and those in the spleen and tibia were lower, in NA rats. The iron concentrations in liver and spleen were positively correlated with the amount of brown pigment as observed histopathologically. Bile flow as well as biliary iron and copper excretion were higher in NA than SD rats. Copper concentrations in liver, kidneys and plasma were higher in NA rats. Plasma levels of ceruloplasmin were about two-fold higher in NA rats. The feeding of a high-iron diet reduced kidney copper concentrations in both strains of rats, which was associated with a decrease in the absorption and biliary excretion of copper.

Extent of bilateral collateralization among pontomesencephalic tegmental afferents to dorsal lateral geniculate nuclei of pigmented and albino rats

In adult pigmented and albino rats, small amounts of different fluorescent dyes (Fast Blue and Fluoro-Gold) were pressure-injected into the dorsal lateral geniculate nuclei, each nucleus (right or left) being injected with one dye only. After postinjection survival of three days, the distribution of neurons retrogradely labelled by each dye was analysed. Consistent with previous studies, in each strain each dye labelled a large number of neurons in the several ipsilateral visuotopically or retinotopically organized structures--visual cortices, retino-recipient layers of the superior colliculi and the pretectal nuclei. A substantial number of retrogradely labelled neurons was also found in the contralateral parabigeminal nucleus. A few retrogradely labelled neurons were found in the ipsilateral and (to a lesser extent) contralateral dorsolateral divisions of the periaqueductal gray matter, as well as in the ipsilateral parabigeminal nucleus and the caudal part of the lateral hypothalamus. However, in all the above structures there was a paucity of cells retrogradely labelled with both dyes (double-labelled cells). By contrast, in each strain, several "modulatory" nuclei (containing cholinergic and aminergic cells) of the pontomesencephalic tegmentum--dorsal raphe, pedunculopontine tegmental nucleus, parabrachial nucleus, laterodorsal tegmental nucleus and locus coeruleus--contained significant numbers of cells projecting to both ipsilateral and contralateral dorsal lateral geniculate nuclei. In each nucleus, ipsilaterally and contralaterally projecting cells constituted, respectively, about 65-70% and about 30-35% of retrogradely labelled cells. About 25% of the contralaterally projecting cells (i.e. about 5-10% of all retrogradely labelled tegmental neurons) were double-labelled with both dyes. Double-labelled cells were intermingled with single-labelled cells projecting ipsilaterally or contralaterally. The proportions of the ipsilaterally, contralaterally and bilaterally projecting neurons in the modulatory components of the pontomesencephalic tegmentum were virtually identical in pigmented and albino strains. It appears that in both strains the visuotopically organized structures convey to the dorsal lateral geniculate nuclei information related mainly to the contralateral visual field. The projections from these structures might play an important role in regulating transmission of visual information in the retinotopically distinct parts of each dorsal lateral geniculate nucleus. By contrast, the projections from the modulatory nuclei of the pontomesencephalic tegmentum are likely to contribute to the functional synchronization of both dorsal lateral geniculate nuclei during the sleep-wakefulness cycle and saccadic eye movements.

Establishment of new inbred strains derived from Japanese wild rats (Rattus norvegicus)

Inbreeding of Japanese wild rats (Rattus norvegicus) resulted in five new strains. The conception rates of wild rat strains were lower than those of inbred laboratory strains, and maternal aggressiveness was observed in some wild strains. The body size of domesticated animals was larger than that of captured ancestors. Two strains have been established as inbred strains; the MITA strain has been tamed to the level of laboratory rats, while the nature of the MITD strain is wild. The MITB strain was derived from the MITA strain as a coat color variant. The MITC and MITE strains have been bred to the F15 and F11 generations, respectively. The new strains can provide new genetic variations against a wild type background and might be useful for physiological and psychological experiments.

Parabigeminal, pretectal and hypothalamic afferents to rat's dorsal lateral geniculate nucleus. Comparison between albino and pigmented strains

In adult pigmented and albino rats different fluorescent dyes were injected into the dorsal lateral geniculate nuclei of opposite sides. Differences between the strains occur mainly in parabigemino-geniculate and pretecto-geniculate projections. Both the major contralateral and the minor ipsilateral parabigemino-geniculate projections in albinos were clearly smaller then those in pigmented rats. In pigmented rats but not in albinos the parabigemino-geniculate projections originated mainly from the region where the vertical meridian is represented and contained a small number of neurones projecting bilaterally. In each strain, a small number of retrogradely labelled neurones was found in the ipsilateral and contralateral lateral hypothalami.

Morphology of neurons in the thalamic reticular nucleus (TRN) of mammals as revealed by intracellular injections into fixed brain slices

I have investigated the morphology of neurons in the thalamic reticular nucleus (TRN) by means of intracellular injections in fixed tissue in order to study whether neurons in visual (dorsocaudal part), somatosensory (intermediate part), or limbic/motor (rostral part) sectors in the rat, rabbit, and cat differ morphologically in relation to their different sensory cortical or thalamic inputs. In addition, I have compared the different mammalian species to ask whether there is a morphological difference of TRN neurons according to reported differences in the intrinsic thalamic organisation, for example, due to the presence of GABAergic local circuit neurons in the majority of thalamic nuclei in the cat and the lack of those neurons in most of the rat thalamic nuclei, and presynaptic dendrites in the cat but not in the rat. In all animals investigated so far, neurons in the caudal (visual) and intermediate (somatosensory) part of the TRN have an elongated dendritic morphology in all three species, but some neurons in the rostral part, in particular in dorsal sections, have a distinctive multipolar morphology. Neurons have round, ovoid, or elongated somata ranging in area between 150 and 860 microns 2. In general, 4-8 first order dendrites emerge directly from the two poles of the soma or from a thick stem segment. Most of the dendrites then run parallel to the borders of the nucleus extending for relatively long distances, up to 450 microns, but remain inside the border of the nucleus. Only a few (1-3) dendrites could be observed to run perpendicular to the border of the nucleus and generally only for a short distance (20-70 microns). Some of the smooth first order dendrites give rise to second order dendrites (up to 200 microns in length), which then branch into short (15-70 microns) third order dendrites. Dendritic spines and varicosities, spine-like protusions and/or hair-like processes are mainly found on second and third order dendrites. Surprisingly, the shape, arrangement, and the size of the dendritic field are not strictly related to the shape and size of the nucleus. In mammalian species with a comparatively narrow TRN (rat and cat) the dendritic field size was similar to that in the rabbit with a broad TRN. There was considerable variability in dendritic morphology in the caudal and intermediate parts of TRN. However, in contrast to two recent studies in the rat TRN I have found no obvious basis for classification of neurons in the mammalian TRN according to dendritic morphology.(ABSTRACT TRUNCATED AT 400 WORDS)

Hippocampal morphology and spatially related behavior in Long-Evans and CFY rats

Behavioral responses to novelty in an open field and spatial learning in a radial maze with four arms out of eight reinforced were tested in male and female CFY and Long-Evans rats. Subsequently, the sizes of the total hippocampi and of various hippocampal cell layers and terminal fields at the midseptotemporal level were measured in Timm-stained sections. No strain differences were found in the open field (except for defecation). In the radial maze, Long-Evans rats showed better spatial reference memory capabilities than rats of the CFY strain. The relative sizes of the intra- and infrapyramidal mossy fiber (IIP-MF) projections did not differ between the strains. Within the more variable CFY strain, a positive correlation between the size of the IIP-MF projection and radial maze performance was found. The absolute sizes of the entire hippocampi and all hippocampal layers at the midseptotemporal level were larger in the CFY strain. The size of the suprapyramidal mossy fiber projection was related to the number of granule cells and to the ratio between granule and CA3 pyramidal cells. In contrast, the size of the IIP-MF projection did not correlate with either of these variables. The results indicate that the size of the mossy fiber projection may be determined mainly by the available postsynaptic surface on the dendrites of CA3 pyramidal neurons. Furthermore, an increased number of granule cells and their larger projection to the apical dendrites of pyramidal neurons does not appear to result in physiological changes with behavioral consequences.(ABSTRACT TRUNCATED AT 250 WORDS)

Afferent projections to the cholinergic pedunculopontine tegmental nucleus and adjacent midbrain extrapyramidal area in the albino rat. I. Retrograde tracing studies

The afferent connections of the pedunculopontine tegmental nucleus (PPT) and the adjacent midbrain extrapyramidal area (MEA) were examined by retrograde tracing with wheat germ agglutinin-conjugated horseradish peroxidase (WGA-HRP). Major afferents to the PPT originate in the periaqueductal gray, central tegmental field, lateral hypothalamic area, dorsal raphe nucleus, superior colliculus, and pontine and medullary reticular fields. Other putative inputs originate in the paraventricular and preoptic hypothalamic nuclei, the zona incerta, nucleus of the solitary tract, central superior raphe nucleus, substantia innominata, posterior hypothalamic area, and thalamic parafascicular nucleus. The major afferent to the medially adjacent MEA originates in the lateral habenula, while other putative afferents include the perifornical and lateral hypothalamic area, periaqueductal gray, superior colliculus, pontine reticular formation, and dorsal raphe nucleus. MEA inputs from basal ganglia nuclei include moderate projections from the substantia nigra pars reticulata, entopeduncular nucleus, and a small projection from the globus pallidus, but not the subthalamic nucleus. Dense anterograde labeling was observed in the substantia nigra pars compacta, entopeduncular nucleus, subthalamic nucleus, globus pallidus, and caudate-putamen only following WGA-HRP injections involving the MEA. The results of this study demonstrate that the PPT and MEA share many potential afferents. Remarkable differences were found that support distinguishing between these two nuclei in future studies regarding the functional organization of the midbrain and pons. The results, for example, confirm our previous observations that the largely reciprocal connections between the midbrain and basal ganglia distinguish the MEA from the PPT. Afferents from the lateral habenula and contralateral superior colliculus represent extensions of more traditional basal ganglion circuitry which further delineate the MEA from the PPT. The results are discussed with respect to the important role of the midbrain and pons in behavioral state control and locomotor mechanisms.

Ventral pallido-striatal pathway in the rat brain: a light and electron microscopic study

Most theories of basal ganglia functions have been based on a model circuit in which the flow of information follows a one-way loop proceeding from the cerebral cortex to the striatum, the pallidum/nigra, the thalamus, and then returns to the cortex. However, this model neglects data from several studies that show a direct feedback projection from the pallidum to the striatum. In this study, we have examined this feedback connection in the ventral striopallidal system to determine the morphology and chemical properties of ventral pallido-striatal projection neurons and to determine the morphology of ventral pallidal efferents in the ventral striatum. Fluoro Gold was injected into the ventral striatum to retrogradely label ventral pallidal projection neurons. Substance P immunoreactivity was used as a pallidal marker to delineate the ventral pallidum. The results show that most neurons retrogradely labeled by Fluoro Gold lie in the ventral pallidum. Additional double-labeling experiments show that none of these Fluoro Gold-labeled cells are cholinergic neurons; however, some are immunoreactive for parvalbumin, a calcium-binding protein found in many pallidal neurons. Electron microscopy revealed that the somata and dendrites of these labeled ventral pallidal projection neurons form many synapses with unlabeled terminals. Injection of Phaseolus vulgaris-leucoagglutinin into the ventral pallidum anterogradely labeled many fibers in the ventral striatum. Electron microscopy revealed that these labeled axons form both symmetric and asymmetric synapses with ventral striatal neurons. We have thus confirmed that there is a significant direct projection from the ventral pallidum to the ventral striatum. Whether this projection forms a part of either monosynaptic or polysynaptic feedback loops remains to be clarified. Nevertheless, this pallidostriatal projection must be integrated into the theories on basal ganglia functions.

Retrograde tracing of projections between the nucleus submedius, the ventrolateral orbital cortex, and the midbrain in the rat

The fluorescent tracers fluoro-gold and 1,1'-dioctadecyl-3,3,3,3-tetramethyl indocarbocyanine perchlorate were used as retrograde markers to examine reciprocal connections between the rat nucleus submedius and the ventrolateral orbital cortex. In addition, midbrain projections to each of these regions were examined. In the prefrontal cortex, we found that input from the nucleus submedius terminates rostrally within the lateral and ventral areas of the ventrolateral orbital cortex. Conversely, the cortical input to the nucleus submedius originates from the medial and dorsal parts of the ventrolateral orbital cortex. Our data also demonstrated that neurons from the ventrolateral periaqueductal gray and the raphe nuclei project to the midline nuclei of the thalamus, including a small projection to the nucleus submedius. We further determined that regions within the ventrolateral periaqueductal gray and raphe nuclei project to the ventrolateral orbital cortex, and that these regions overlap with those that project to the nucleus submedius. These findings suggest that the nucleus submedius might be part of a neural circuit involved in the activation of endogenous analgesia.

The hypothalamo-cerebellar projection in the rat: origin and transmitter

Hypothalamic neurons projecting to cerebellum were identified by retrograde tracing with wheat germ agglutinin-horseradish peroxidase (WGA-HRP) in the rat. Selective D-[3H]aspartate labelling was used to investigate whether any of these connections may use excitatory amino acids as transmitters. The WGA-HRP experiments revealed that the hypothalamo-cerebellar fibers have their main origins in the lateral, dorsal and posterior hypothalamic areas, and the tubero-mammillary nucleus, while smaller numbers of cells were observed in tuber cinereum, the anterior hypothalamic area, and the periventricular and paraventricular nuclei. After injections of D-[3H]aspartate into the cerebellar cortex, intense labelling of the olivocerebellar climbing fiber system was observed, but hypothalamic cells were not retrogradely labelled with this selective tracer. The absence of D-[3H]aspartate labelling indicates that hypothalamo-cerebellar neurons lack specific uptake mechanisms for excitatory amino acids, but it does not entirely preclude the possibility that some of these hypothalamic neurons may use such transmitters. Many cerebellar projecting cells were located in the tubero-mammillary nucleus, which is known to contain histaminergic and GABAergic neurons, and it was concluded that part of the hypothalamo-cerebellar pathways may use histamine and/or GABA as transmitters. The transmitter remains unknown for other parts of the hypothalamo-cerebellar pathways.

The role of nasopharyngeal lymphoid tissue

Nasal-associated lymphoid tissue (NALT), which comprises paired lymphoid organs in the nasopharynx of rodents, is the principal mucosal lymphoid tissue of the respiratory tract. As described in this review, NALT bears certain similarities to the Peyer's patches of the intestine but the two differ remarkably in morphology, lymphoid migration patterns and the binding properties of their high endothelial venules (HEV).

Microvascular pattern during the growth of regenerating muscle fibers in the rat

Quantitative methods were used to analyze changes in the capillarization of skeletal muscle during regeneration. The H-E staining technique was used to establish three arbitrary stages of fiber regeneration on the basis of qualitative histological evaluation. ATPase and light microscopic techniques were used to calculate capillary density, the number of capillaries surrounding each fiber, and the fiber area served by each capillary, for each of the three stages established. The results obtained indicated variations in the vascularization of regenerating fibers from one stage of maturity of another: capillarization was greater in the initial stages of regeneration, returning gradually to normal values by the final stages of the process. Interestingly enough the pattern in the capillarization of skeletal muscle during regeneration seems to be similar to that taking place during postnatal muscle development. Both processes appear to be governed by the increase in fiber size.

[Histological observations on structure of endomysium, perimysium and epimysium of lateral pterygoid muscle in rat]

To understand the muscle as a locomotorium, I observed the structure of the connective tissue sheaths (the endomysium, the perimysium and the epimysium) in the mature rat lateral pterygoid muscle. The following results were obtained using the macroscopy and light and electron microscopy. The lateral pterygoid muscle consists of two parts. The superior head originates from the basisphenoid and is mainly inserted into the articular disk and capsule. The inferior head originates from the lateral pterygoid processus and is mainly inserted into the condylar processus of the mandible. The perimysium is thick and bound the fasciculus secondarily as sheaths near the insertion of the superior head. The collagenous fibers are very fine in the endomysium. The collagenous fibers that make the connective tissue sheaths arrange on a skew against the muscle fibers, but parallel around the origin and the insertion. It seems that the connective tissue sheaths in the rat lateral pterygoid muscle, in view of the morphology, retain the forms of fasciculus, act as the runways for the muscle fibers in time of expansion and contraction and offer spaces for the attachment of the muscle fibers.

Vagal afferent innervation of the rat fundic stomach: morphological characterization of the gastric tension receptor

Although the gastric tension receptor has been characterized behaviorally and electrophysiologically quite well, its location and structure remains elusive. Therefore, the vagal afferents to the rat fundus (forestomach or nonglandular stomach) were anterogradely labeled in vivo with injections of the carbocyanine dye Dil into the nodose ganglia, and the nerves and ganglia of the enteric nervous system were labeled in toto with intraperitoneal Fluorogold injection. Dissected layers and cryostat cross sections of the fundic wall were mounted in glycerin and analyzed by means of conventional and laser scanning confocal microscopy. Particularly in the longitudinal, and to a lesser extent in the circular, smooth muscle layers, Dil-labeled fibers and terminals were abundant. These processes, which originated from fibers coursing through the myenteric ganglia and connectives, entered either muscle coat and then ran parallel to the respective muscle fibers, often for several millimeters. They ran in close association with the Fluorogold-labeled network of interstitial cells of Cajal, upon which they appeared to form multiple spiny appositions or varicosities. In the myenteric plexus, two different types of afferent vagal structures were observed. Up to 300 highly arborizing endings forming dense accumulations of small puncta similar to the esophageal intraganglionic laminar endings (Rodrigo et al., '75 Acta Anat. 92:79-100) were found in the fundic wall ipsilateral to the injected nodose ganglion. They often covered small clusters of myenteric neurons or even single isolated ganglion cells (mean = 5.8 neurons) and tended to extend throughout the neuropil of the ganglia. In a second pattern, fine varicose fibers with less profuse arborizations innervated mainly the central regions of myenteric ganglia. Camera lucida analyses established that single vagal afferent fibers had separate collaterals in both a smooth muscle layer and the myenteric ganglia. Finally, Dil-labeled afferent vagal fibers were also found in the submucosa and mucosa. Control experiments in rats with supranodose vagotomy as well as rats with Dil injections directly in the distal cervical vagus ruled out the possibility of colabeling of afferent fibers of passage. In triple labeling experiments, in conjunction with Dil labeling of afferents and Fluorogold labeling of enteric neurons, the carbocyanine dye DiA was injected into the dorsal motor nucleus of the vagus to anterogradely label the efferent vagal fibers and terminals. The different distributions and morphological characteristics of the vagal afferents and efferents could be simultaneously compared. In some instances the same myenteric ganglion was apparently innervated by an afferent laminar ending and an efferent terminal.(ABSTRACT TRUNCATED AT 400 WORDS)

Frog cones as well as Müller cells have peroxisomes

We have localized D-amino acid oxidase in peroxisomes of frog retina using cerium procedures on tissue fixed in mixtures containing lower concentrations of glutaraldehyde than we had previously used in our cytochemical studies of this enzyme. We find the Müller cells of these preparations contain a more striking population of peroxisomes than had previously been thought: the D-amino acid oxidase-containing bodies are especially concentrated near the outer limiting membrane, but appreciable numbers are also found in the outer plexiform layer and near the inner limiting membrane. In addition, we find peroxisomes to be present in frog cone photoreceptors, particularly in zones near the ellipsoid. To our knowledge peroxisomes have not been described hitherto in vertebrate photoreceptors. Possible roles for the peroxisomes of the neural retina include participation in the metabolism of lipids (e.g. those of the cones' oil droplets, or of the outer segment) and involvement in oxidation of transmitter-related amino acids and of other small molecules.

Demonstration of a neuronal projection from the entopeduncular nucleus to the substantia nigra of the rat

The two neuronal tracers, Phaseolus vulgaris leucoagglutinin (PHA-L) and Cholera toxin subunit B (CHB) were used in order to study a possible neuronal projection from the entopeduncular nucleus to the ventral mesencephalon in the rat. Both tracers were identified in brain sections by means of immunohistochemistry. After injection of PHA-L in the entopeduncular nucleus PHA-L-positive nerve fibers observed in the mesencephalon were moderate in number and mostly restricted to the mediodorsal part of the substantia nigra, pars reticulata. In addition, a low number of PHA-L-immunoreactive nerve fibers was found in the substantia nigra, pars compacta, the rostral part of the ventral tegmental area, and in the deep mesencephalic nucleus. In agreement with these observations, several labeled neurons were observed in the ipsilateral entopeduncular nucleus after injections of CHB in the substantia nigra. These results indicate the presence of a direct neuronal projection between the two major output channels of the basal ganglia.

A sexually dimorphic population of galanin-like neurons in the rat lumbar spinal cord: functional implications

The rat lumbar spinal cord contains a population of galanin- and cholecystokinin-containing neurons which are located dorsolateral to the central canal and project to the thalamus. New data are presented herein which reveal that the number of these neurons, as shown by galanin-like immunostaining, is sexually dimorphic with males containing 62% more of these neurons than females. This is the first demonstration of a sexually dimorphic population of intraspinal neurons which projects to higher CNS centers rather than to peripheral targets.

Immunocytochemical study of the ultimobranchial tubule in Wistar rats

A systematic immunohistochemical study of the ultimobranchial tubule (UBT) has been carried out in 45 Wistar rats of different ages (0, 5, 10, 15, 20, 25, 30, 60 and 120 days). The existence of calcitonin immunoreactive cells in the UBT wall has been demonstrated in a 5-days old rat. In addition, immunohistochemical studies for thyroglobulin revealed positive staining in follicular cells connected to the UBT and, occasionally, in isolated cells lying within solid clusters from the UBT. These last results together with the continued and repeated existence of numerous mitosis and PAS (+) microfollicles, apparently rising from the UBT, support the hypothesis that the ultimobranchial body (UBB) may contribute partially to the formation of a part of the follicular component.

Adenomatoid odontogenic tumorlike lesion in a male Wistar rat

An odontogenic tumor in the maxilla of a male Wistar rat is described. The tumor consisted of large epithelial areas with peripheral palissading and with juxtaepithelial material resembling dentin. The neoplastic odontogenic epithelium seems capable of inducing peridental mesenchyme to form a kind of dental hard tissue normally not present at that site.

Cell types in the main excretory duct of the submaxillary gland of the rat

This work is an ultrastructural study of the cells of the excretory duct epithelium of the submaxillary gland of the rat. This epithelium undergoes progressive loss of cytoplasm which leads to the presence of three distinct types of cell.

Vasoactive intestinal polypeptide and acetylcholine coexist with neuropeptide Y, dopamine-?-hydroxylase, tyrosine hydroxylase, substance P or calcitonin gene-related peptide in neuronal subpopulations in cranial parasympathetic ganglia of rat

Immunohistochemistry has been used to demonstrate that neuropeptide Y, dopamine-beta-hydroxylase, calcitonin gene-related peptide or substance P are colocalized with vasoactive intestinal polypeptide and choline acetyltransferase in subpopulations of neurons in cranial parasympathetic ganglia of rat. These comprise the ciliary, sphenopalatine, otic, glossopharyngeal-vagal and internal carotid ganglia. In the ciliary and glossopharyngeal-vagal ganglia tyrosine hydroxylase is also found in such neurons. The findings emphasize that the combined localization of dopamine-beta-hydroxylase and neuropeptide Y or the presence of tyrosine hydroxylase is not exclusively a marker for peripheral adrenergic neurons. Further, the co-localization of calcitonin gene-related peptide and substance P is not a decisive indication that a neuron is sensory in nature. It is discussed whether the presence of the enzymes and peptides other than vasoactive intestinal polypeptide is a remnant of a different expression during ontogenesis or indicates target-specific functions in the adult.

Animal prostate carcinoma models: limited potential for vertebral metastasis

Several methods for induction of rat prostate carcinomas are now available. The induced adenocarcinomas, which develop normally in the lateral and/or dorsal prostate, are invasive and can form distant metastases. Metastatic sites include the abdominal cavity, liver, lung, and/or lymph nodes but, as yet, bone metastasis of prostate cancers in experimental animals has not been reported, despite its being very common in man. Anatomical and hemodynamic differences seem to be account for this lack of bone metastasis.

Organization of medullary adrenergic and noradrenergic projections to the periaqueductal gray matter in the rat

The periaqueductal or midbrain central gray matter (CG) in the rat contains a dense network of adrenergic and noradrenergic fibers. We examined the origin of this innervation by using retrograde and anterograde axonal tracers combined with immunohistochemistry for the catecholamine biosynthetic enzymes tyrosine hydroxylase (TH), dopamine beta-hydroxylase (DBH), and phenylethanolamine N-methyltransferase (PNMT). Following injections of the fluorescent tracers Fast Blue or Fluorogold into the CG, double-labeled neurons in the medulla were identified mainly in the noradrenergic A1 group in the caudal ventrolateral medulla (VLM) and A2 group in the medial part of the nucleus of the solitary tract (NTS); and in the adrenergic C1 group in the rostral ventrolateral medulla and C3 group in the rostral dorsomedial medulla. Injections of Phaseolus vulgaris-leucoagglutinin (PHA-L) into these cell groups resulted in a distinct pattern of axonal labeling in various subdivisions of the CG. Anterogradely labeled fibers originating in the medial NTS were predominantly found in the lateral portion of the dorsal raphe nucleus and in the adjacent part of the lateroventral CG (CGlv). Following PHA-L injections into the C3 region the anterogradely labeled fibers were diffusely distributed in the CGlv and the dorsal raphe nucleus at caudal levels, but rostrally tended to be located laterally in the CGlv. In contrast, ascending fibers from the caudal and rostral VLM terminated in the rostral dorsal part of the CGlv and in the dorsal nucleus of the CG, whereas ventral parts of the CG, including the dorsal raphe nucleus, contained few afferent fibers. Double-label studies with antisera against DBH and PNMT confirmed that noradrenergic neurons in the A1 and A2 groups and adrenergic neurons in the C1 and C3 groups contributed to these innervation patterns in the CGlv. Noradrenergic and adrenergic projections from the medulla to the CG may play an important role in a variety of autonomic, sensory and behavioral processes.

The development of ventral tegmental area (VTA) projections to the visual cortex of the rat

The development of the ventral tegmental area (VTA) projections to the rat visual cortex was studied with the wheat germ agglutinin-horseradish peroxidase (WGA-HRP) retrograde tracing technique. Large injections of WGA-HRP in the visual cortex of newborn, early postnatal, and adult rats resulted in a substantial number of retrogradely labelled neurons in the VTA showing the same distribution pattern at all ages examined. Contrary to other reports, labelled cells were never found in the pars compacta of the substantia nigra but occasionally were seen in the contralateral VTA near the midline. These neurons showed a continuous growth from the day of birth to the end of the second postnatal week, when they acquired morphological features comparable to the adult; they subsequently showed a substantial decrease in soma size. The present results clearly demonstrate that there exists a substantial mesocortical projection to the rat visual cortex which arises exclusively from the VTA. This projection is already established at birth, but the neurons which give rise to it appear morphologically immature during the first two postnatal weeks.

Afferent and sympathetic neurons projecting into lumbar visceral nerves of the male rat

The cell bodies of thoracolumbar sensory and sympathetic pre- and postganglionic neurons that project to the colon and pelvic organs of the male rat were labeled retrogradely with horseradish peroxidase (HRP) in order to study numbers, segmental distribution, and location of the somata of these neurons quantitatively. HRP was applied to one hypogastric nerve (HGN), to the lumbar colonic nerves (LCN) and to the intermesenteric nerve (IMN). In order to estimate the significance of the branching of one axon into both hypogastric nerves a double-labeling technique with fluorogold and HRP was used. About 2640 neurons project into the two HGN added together (800 afferent, 1320 pre-, and 520 postganglionic), 4650 neurons into the LCN (360 afferent, 0 pre- and 4290 postganglionic), and 5990 into the IMN (1500 afferent, 1250 pre-, and 3240 postganglionic). About 4190 sympathetic postganglionic prevertebral neurons innervate the colon and pelvic organs, 1900 are located in the inferior mesenteric ganglion and 2290 in ganglia of the IMN. Considering the efferent component, the HGN mainly are preganglionic and the LCN exclusively postganglionic nerves. Branching of one axon into both HGN is a rare event and quantitatively negligible (less than 3%). Afferent neurons of all three nerves were found in the dorsal root ganglia (DRG) T12-L2 with the maximum in L1 and L2. The distribution of afferent neurons projecting into the LCN is shifted slightly more rostrally compared to neurons projecting into the HGN. The IMN distribution is located in a position in between. Preganglionic neurons projecting into the IMN are located in the spinal cord segments T12-L3 with the maximum in L1 and L2.(ABSTRACT TRUNCATED AT 250 WORDS)

Thalamic processing of vibrissal information in the rat. I. Afferent input to the medial ventral posterior and posterior nuclei

Retrograde tracing with true blue (TB) and diamidino yellow (DY) and anterograde tracing with either wheatgerm agglutinin-conjugated horseradish peroxidase (WGA-HRP) or Phaseolus vulgaris leucoagglutinin (PHA-L) were employed to investigate the projections from trigeminal nucleus principalis (PrV) and trigeminal subnucleus interpolaris (SpI) to their targets in the medial ventral posterior (VPM) and posterior (POm) nuclei of the thalamus. Many more cells in both PrV and SpI were labeled by tracer injections into VPM than into POm. Only a very small number of double-labeled neurons were observed in either PrV or SpI. However, a significantly higher percentage of SpI cells projected to POm or to both POm and VPM than was the case for PrV. Anterograde tracing with WGA-HRP showed that the projections from both PrV and SpI to VPM were much denser than those from the same nuclei to POm. Small injections of PHA-L into either PrV or SpI produced a focus of fairly dense labeling in VPM and much more diffuse terminal labeling in POm. These anatomical data provide evidence for two separate trigeminothalamic pathways, one originating from PrV and the second originating from SpI. Both of these pathways converge and diverge at the thalamic level. That is, information from the PrV pathway and from the SpI pathway are both provided to VPM in a morphologically restricted fashion and to POm in a morphologically widespread fashion.

Efferent projections of the infralimbic (area 25) region of the medial prefrontal cortex in the rat: an anterograde tracer PHA-L study

The efferent projections of the infralimbic region (IL) of the medial prefrontal cortex of the rat were examined by using the anterograde transport of Phaseolus vulgaris leucoagglutinin (PHA-L). Major targets of the IL were found to include the agranular insular cortex, olfactory tubercle, perirhinal cortex, the whole amygdaloid complex, caudate putamen, accumbens nucleus, bed nucleus of the stria terminalis, midline thalamic nuclei, the lateral preoptic nucleus, paraventricular nucleus, supramammillary nucleus, medial mammillary nucleus, dorsal and posterior areas of the hypothalamus, ventral tegmental area, central gray, interpeduncular nucleus, dorsal raphe, lateral parabrachial nucleus and locus coeruleus. Previously unreported projections of the IL to the anterior olfactory nucleus, piriform cortex, anterior hypothalamic area and lateroanterior hypothalamic nucleus were observed. The density of labeled terminals was especially high in the agranular insular cortex, olfactory tubercle, medial division of the mediodorsal nucleus of the thalamus, dorsal hypothalamic area and the lateral division of the central amygdaloid nucleus. Several physiological and pharmacological studies have suggested that the IL functions as the 'visceral motor' cortex, involved in autonomic integration with behavioral and emotional events. The present investigation is the first comprehensive study of the IL efferent projections to support this concept.

Atlas of the rat brain: quantitative distribution of the choline acetyltransferase

We have developed a fluorescence microphotometry system for microanalysis of the quantitative distribution of neurotransmitters and their related chemical substances in the brain slice. In the present study, the extensive distributions of cholinergic systems were analyzed quantitatively and in detail throughout the rat whole brains by this novel method through immunohistochemical staining of choline acetyltransferase (CAT). The rat whole brain was slice coronally and continuously, and 50 slices were chosen at approximately 500 microns intervals and stained immunohistochemically for CAT. Immunohistochemical fluorescence intensities were measured through a 6 microns phi (on the slice) pinhole of a microscope, the brain slice was moved along the X- or Y-axes stepwise at 40 microns intervals under the objective lens of the microscope, and the distributions of fluorescence intensities were analyzed over the entire surface of the slice. The brain was divided into approximately 5,000,000 areas, and immunohistochemical fluorescence intensities of those areas were quantitatively measured. The obtained fluorescence intensities of CAT were classified into 8 ranks and were indicated by color coding and by three-dimensional graphics. Also, the actual fluorescence intensity values in large brain regions were presented. This type of brain atlas of the neurotransmitter or its related chemical substances provides very important information on their dynamics in the brain under experimental as well as pathological conditions. Also, this quantitative and detailed analysis is useful for combining morphological data with those from neurochemical and behavioral analyses of brain function.

Distribution of choline acetyltransferase immunoreactive axons and terminals in the rat and ferret brainstem

A survey was made of the density of the cholinergic innervation of different parts of the brainstem of the rat and ferret. Sections of rat and ferret brainstems were stained for choline acetyltransferase (ChAT) immunoreactivity by using a sensitive immunocytochemical method. Adjacent sections were stained for acetylcholinesterase activity or Nissl substance. The density of the distribution of fine calibre, varicose ChAT-positive axons, assumed to represent cholinergic terminals, was categorised arbitrarily into high, medium, or low. A high density of ChAT-positive terminals was found in all or parts of these structures: interpeduncular nucleus, superficial grey layer of the superior colliculus (ferret), intermediate layers of the superior colliculus, lateral part of the central grey (rat), an area medial to the parabigeminal nucleus (rat), pontine nuclei, ventral tegmental nucleus (rat), midline pontine reticular formation, and an area ventral to the exit point of the 5th nerve (ferret). A medium density of ChAT-positive terminals was observed in all or parts of: the substantia nigra zona compacta (ferret), ventral tegmental area (ferret), superficial grey layer of the superior colliculus, intermediate and deep layers of the superior colliculus, lateral central grey, area medial to the parabigeminal nucleus, inferior colliculus, dorsal tegmental nucleus, ventral tegmental nucleus (ferret), pontine nuclei, ventral nucleus of the lateral lemniscus (ferret), midline pontine reticular formation, ventral cochlear nucleus, dorsal cochlear nucleus, lateral superior olive, spinal trigeminal nuclei, prepositus hypoglossal nucleus, lateral reticular nucleus, paragigantocellular nucleus, and the dorsal column nuclei including the cuneate, external cuneate, and gracile nuclei. A low density of ChAT-positive terminals was seen throughout the remainder of the brainstem of the rat and ferret, but these terminals were absent from the medial superior olive, substantia nigra zona reticulata (rat), and the central part of the ferret lateral superior olive. A pericellular-like distribution of ChAT-positive terminals was observed in the ventral cochlear nucleus and in association with some of the cells of the nucleus of the mesencephalic tract of the trigeminal nerve. A climbing fibre type arrangement of ChAT-positive terminals was found in the substantia nigra zona compacta (ferret) and medial reticular formation. In general, the distribution of staining for AChE activity reflected that of the distribution of ChAT immunoreactivity in the brainstem, except in a few regions where there were also species differences in the distribution of ChAT-positive terminals, e.g., in the superficial grey layer of the superior colliculus and in the substantia nigra.(ABSTRACT TRUNCATED AT 400 WORDS)

Thalamoamygdaloid projections in the rat: a test of the amygdala's role in sensory processing

We used the autoradiographic tract-tracing method to define the amygdaloid projection fields after injecting 3H-amino acids into individual thalamic nuclei in the rat. The parvicellular division of the ventroposterior nucleus, the thalamic taste relay, projected lightly to the central and lateral amygdaloid nuclei. The central medial, interanteromedial, and paraventricular thalamic nuclei, viscerosensory relays of the thorax and abdomen, projected heavily to the amygdala. All projected to the basolateral amygdaloid nucleus, the paraventricular nucleus in addition having terminations in the central nucleus, the amygdaloid portion of the nucleus of the stria terminalis, and the amygdalohippocampal transition area. The magnocellular division of the medial geniculate, a thalamic auditory (and, to a moderate degree, a spinothalamic) relay, sent heavy projections to the central, accessory basal, lateral, and anterior cortical nuclei, and to the anterior amygdaloid area and the nucleus of the accessory olfactory tract. Other thalamic nuclei projecting to the amygdala, for which functions could not be associated, were the paratenial and subparafascicular nuclei. The former projected to the lateral, basal, and posterolateral cortical nuclei; the latter projected very lightly to the central, medial, and basal accessory nuclei. These results show that, like the cortical amygdaloid nuclei, which are sensory (olfactory) in nature, the subcortical amygdaloid nuclei must have major sensory functions. These thalamic afferents, when correlated with cortical and brainstem data from the literature, suggested that the amygdala is in receipt of sensory information from many modalities. To uncover the manner by which such information is processed by the amygdala and relayed to effector areas of the brain, six hypothetical mechanisms relating to modality specificity and convergence were posited. By charting sensory-related afferents to all subdivisions of the amygdala, each nucleus was characterized as to its mechanism of information processing. Four proposed amygdaloid systems emerged from this analysis. A unimodal corticomedial amygdaloid system relays pheromonal information from the accessory olfactory bulb to medial basal forebrain and hypothalamic areas. A second system--the lateral-basomedial--collects and combines input from a number of sensory modalities and distributes it to the same basal forebrain and hypothalamic areas as the corticomedial. The central system appears to concentrate the effect of viscerosensory information arriving from multiple brainstem, thalamic, cortical, and amygdaloid sources; this information is combined with significant auditory and spinothalamic inputs from the thalamus and cortex. The central system projects to lateral nuclei in the basal forebrain, hypothalamus, and brainstem.(ABSTRACT TRUNCATED AT 400 WORDS)

Rat central amygdaloid nucleus projections to the bed nucleus of the stria terminalis

The projections from the central amygdaloid nucleus (Ce) to different subdivisions of the bed nucleus of the stria terminalis (BNST) were investigated using retrograde transport of fluorescent dyes. Iontophoretic injections of either Fast Blue (FB) or bisbenzimide (BB) were applied to the anterior medial, posterior medial, anterior lateral and posterior lateral parts of the bed nucleus of the stria terminalis. The anterior medial BNST receives projections from caudal part of medial Ce (CeM). The posterior medial BNST receives projections specifically from the intermediate subdivision of Ce, though in some cases projections from the ventral subdivision (CeV) of Ce were seen. The anterior lateral BNST receives projections primarily from the caudal lateral Ce (CeL) as well as middle and caudal part of CeM. The posterior lateral BNST receives projection from rostral CeL as well as the CeV and lateral capsular Ce. In general, the results indicate that the major subdivisions of the BNST receive projections from Ce subdivisions having similar connections with diencephalic or brainstem cell groups. Additional evidence is presented suggesting that Ce-BNST projections are part of an extensive system of intrinsic connections linking similar groups of neurons in both the Ce and BNST as well as within Ce.

Sexually dimorphic, androgen sensitive, enkephalinergic afferents to a lumbar motor nucleus of rats

In male rats, methionine-enkephalin immunoreactivity (enkephalin-ir) has been observed in the dorsal lateral nucleus (DLN), a longitudinal pool of motoneurons in the lumbar spinal cord. Within the DLN a mediodorsal crescent of intense enkephalin-ir staining surrounds the motoneurons innervating the ischiocavernosus muscle of the penis, which suggests a function of the enkephalinergic afferents in male copulatory activities. The present study attempted to determine the roles of gender and adult exposure to androgen in shaping the striking subnuclear distribution of enkephalin-ir. Transverse sections through L5-6 were obtained from mature male and female rats that were gonadally intact, gonadectomized, or gonadectomized and treated with testosterone, as well as from male rats genetically deficient in androgen receptors (Tfm). The sections were incubated with primary antiserum raised against methionine enkephalin and bound antibodies were visualized using the avidin-biotin-peroxidase technique. A microphotometer was used to compare the staining density in laminae I-II of the dorsal horn, ventral grey matter, and the DLN. In all groups the DLN stained more darkly than the ventral grey, demonstrating the presence of enkephalin-ir in the DLN regardless of gender or exposure to androgen. However, the mediodorsal crescent of dense staining in the DLN was obvious only in gonadally intact males, while the entire DLN stained darkly in both sexes of gonadectomized rats treated with androgen. Therefore, the preferential distribution of enkephalin-ir in the mediodorsal crescent of the DLN is sexually dimorphic though the overall content of enkephalin-ir within the DLN responds to androgen.

Investigations of origins of serotonergic projection to developing rat visual cortex: a combined retrograde tracing and immunohistochemical study

The present study investigated whether the raphe neurons which give rise to the transient serotonergic fibers in the visual cortex of neonatal rats persist or disappear as the rats mature. Three experiments were performed employing the WGA-apoHRP-Au retrograde transport technique in conjunction with 5-HT or WGA-HRP immunohistochemical staining. WGA-apoHRP-Au was injected into the primary visual cortex of all rats 9 days postnatally. In the first experiment, the animals were examined after 2 days; retrogradely labeled cells were observed in the dorsal raphe nucleus (DR), the median raphe nucleus (MR), and in the B9 and B6 cell groups; the majority (82.5%) of the cells was serotonergic. In the second experiment, the examinations took place following a survival time of 8 weeks: virtually all of the original raphe-visual cortical serotonergic neurons were found to the present. In the third experiment, also performed after 8 weeks relabeling the raphe-visual cortical neurons by WGA-HRP, it was found that 37.2% of the raphe neurons which had projected to the neonatal visual cortex no longer possessed such projections.

Pallidotectal projection to the inferior colliculus of the rat

After injection of fluorescent tracer into the inferior colliculus (IC), retrogradely labeled cells were observed not only in the temporoauditory cortex (ACx) and the substantia nigra pars lateralis, but also in the globus pallidus (GP). These labeled GP cells were localized exclusively in the caudal portion of the GP, which has been known to project to the ACx. Employing a retrograde fluorescent double labeling technique, the GP-IC neurons were found to be distributed in a separate manner from the GP-ACx neurons within the caudal GP. The present study provides further anatomical evidence that the caudal GP has a functional role in auditory processing.

Sectional anatomy of the pelvis in the male rat with ultrasound correlations

Ten-week-old male Wistar rats were used for sectional anatomy and ultrasonic diagnosis of the pelvis. The prostate and the urinary bladder were identified easily on longitudinal section by ultrasound examination. The prostate (ventral, lateral, and dorsal lobes) was located in the midline of the pelvis cavity on transverse sections and the caudal side of the urinary bladder on longitudinal sections. The urinary bladder was positioned at the cranial side of the prostate on longitudinal sections and in the midline of the pelvis cavity on transverse sections. The seminal vesicles were located at right and left positions of the urinary bladder. Ultrasonic diagnosis was estimated to be useful for experimental studies and we hope that ultrasound techniques may reduce the number of rats used for the treatment of prostate and urinary bladder cancers.

Morphological alteration of gut-associated lymphoid tissue after long-term total parenteral nutrition in rats

The morphological alteration of gut-associated lymphoid tissue (GALT) induced by long-term absence of dietary stimulation was investigated. Male Wistar rats weighing approximately 230 g were maintained with total parenteral nutrition (TPN). Control rats were allowed to have the same amount of the solution orally. After two weeks, the morphological alteration of GALT was examined. Although no significant difference in weight gain was noted between the two groups, the area comprised by Peyer's patches was decreased in TPN rats. The number of transported lymphocytes and the ratio of helper T (Th) cells to suppressor/cytotoxic T (Ts/c) cells in intestinal lymph were lowered after TPN treatment. In an immunohistochemical study of the rat ileum, the number of T cells and the Th/Ts/c ratio were decreased both in the intraepithelial spaces and in the lamina propria of TPN rats. The percentage of interleukin-2 receptor-positive cells and the number of IgA-containing cells in the lamina propria were significantly reduced in TPN rats. These results suggest that dietary stimulation might play a role in the maintenance of GALT function and morphology.