A multicontrast MR atlas of the Wistar rat brain

We describe a multi-contrast, multi-dimensional atlas of the Wistar rat acquired at microscopic spatial resolution using magnetic resonance histology (MRH). Diffusion weighted images, and associated scalar images were acquired of a single specimen with a fully sampled Fourier reconstruction, 61 angles and b=3000 s/mm2 yielding 50 um isotropic spatial resolution. The higher angular sampling allows use of the GQI algorithm improving the angular invariance of the scalar images and yielding an orientation distribution function to assist in delineating subtle boundaries where there are crossing fibers  and track density images providing insight into local fiber architecture.  A multigradient echo image of the same specimen was acquired at 25 um isotropic spatial resolution. A quantitative susceptibility map enhances fiber architecture relative to the magnitude images.  An accompanying multi-specimen atlas (n=6) was acquired with compressed sensing with the same diffusion protocol as used for the single specimen atlas.  An average was created using diffeomorphic mapping. Scalar volumes from the diffusion data, a T2* weighted volume, a quantitative susceptibility map, and a track density volume, all registered to the same space provide multiple contrasts to assist in anatomic delineation. The new template  provides significantly increased contrast in the scalar DTI images when compared to previous atlases. A compact interactive viewer based on 3D Slicer is provided to facilitate comparison among the contrasts in the multiple volumes. The single volume and average atlas with multiple 3D volumes provide an improved template for anatomic interrogation of the Wistar rat brain. The improved contrast to noise in the scalar DTI images and the addition of other volumes (eg. QA,QSM,TDI ) will facilitate automated label registration for MR histology and preclinical imaging.

Anthropometrical parameters and markers of obesity in rats

The present study was undertaken to determine anthropometrical parameters in male adult Wistar rats. We tested the hypothesis that the anthropometrical index may identify obesity and may predict its adverse effects on lipid profile and oxidative stress in rats. Two experimental protocols were performed. In the first experiment, 50 male Wistar rats, 21 days old and fed a control chow were studied up to 150 days of age. In the second experiment, male Wistar rats, 60 days old, were divided into three groups ( n = 8): control (C) given free access to a control chow; (S) receiving the control chow and drinking 30% sucrose ad libitum and (HC) fed a high-carbohydrate diet ad libitum. The first experiment showed that food consumption, energy intake and body weight increased with increasing age, while specific rate of body mass gain was significantly decreased. There were no significant differences in body length and thoracic circumference of rats from 60 days of age. The abdominal circumference (AC) and body mass index (BMI) significantly increased with enhancing age in rats up to 90 days of age and remained constant thereafter. In the second experiment, after 30 days of dietary treatment, the final body weight, body mass gain, carcass fat and BMI were higher in S and HC rats than in C. There were no significant alterations in body length and carcass protein among the groups. Triacylglycerol (TG), total cholesterol (CT), low-density lipoprotein cholesterol (LDL-C) and lipid hydroperoxide (LH) were higher in S and HC rats than in C. High-density lipoprotein cholesterol (HDL-C) decreased in HC rats and total antioxidant substances (TAS) decreased in S and HC rats. There were positive correlations between BMI with carcass fat, BMI with LH and BMI and serum TG concentration. In conclusion, the BMI for male adult Wistar rats ranged between 0.45 and 0.68 g/cm2. Obesity may be easily estimated from the BMI in rats. Alterations in BMI were associated with dyslipidemic profile and oxidative stress in serum of rats and BMI may predict these adverse consequences of the obesity in rats.

Variability in the cardiac venous system of Wistar rats

Rats are often used as animal models in experimental cardiology for studying myocardial infarctions and various cardiologic procedures. Currently the cardiac venous system is a target for the delivery of drugs, gene vectors, angiogenetic growth factors, stem cells, and cardioprotective reagents. The purpose of this study was to describe the anatomic configuration and variability of the cardiac venous system in Wistar rats, by using the corrosion cast method and perfusion of colored latex. The distribution of veins in the rat heart disagrees with prior descriptions for other mammals, except mice, which have a similar pattern. Coronary venous drainage in the 36 rats examined consistently involved the left cardiac, left conal, major caudal, right cardiac, and right conal veins. Other veins involved inconsistently included the cranial cardiac vein (58.3% of cases), minor caudal veins (16.7%), conoanastomotic vein (66.7%), and left atrial vein (75%). In 4 cases (11.1%), the collateral veins were located between the left conal and left cardiac veins. In this study, high morphologic variability between cases was manifested by differences in the arrangement, size, mode of opening, and formation of the common root and affected all regions of the heart but primarily the right ventricle.

A multidimensional magnetic resonance histology atlas of the Wistar rat brain

We have produced a multidimensional atlas of the adult Wistar rat brain based on magnetic resonance histology (MRH). This MR atlas has been carefully aligned with the widely used Paxinos-Watson atlas based on optical sections to allow comparisons between histochemical and immuno-marker data, and the use of the Paxinos-Watson abbreviation set. Our MR atlas attempts to make a seamless connection with the advantageous features of the Paxinos-Watson atlas, and to extend the utility of the data through the unique capabilities of MR histology: a) ability to view the brain in the skull with limited distortion from shrinkage or sectioning; b) isotropic spatial resolution, which permits sectioning along any arbitrary axis without loss of detail; c) three-dimensional (3D) images preserving spatial relationships; and d) widely varied contrast dependent on the unique properties of water protons. 3D diffusion tensor images (DTI) at what we believe to be the highest resolution ever attained in the rat provide unique insight into white matter structures and connectivity. The 3D isotropic data allow registration of multiple data sets into a common reference space to provide average atlases not possible with conventional histology. The resulting multidimensional atlas that combines Paxinos-Watson with multidimensional MRH images from multiple specimens provides a new, comprehensive view of the neuroanatomy of the rat and offers a collaborative platform for future rat brain studies.

Organization of anterior cingulate and frontal cortical projections to the retrosplenial cortex in the rat

The retrosplenial cortex (areas 29a-d), which plays an important role in spatial memory and navigation, is known to provide massive projections to frontal association and motor cortices, which are also essential for spatial behavior. The reciprocal projections originating from these frontal cortices to areas 29a-d, however, have been analyzed to only a limited extent. Here, we report an analysis of the anatomical organization of projections from anterior cingulate area 24 and motor and prefrontal cortices to areas 29a-d in the rat, using the axonal transport of cholera toxin B subunit and biotinylated dextran amine. Area 29a receives projections from rostral area 24a, area 24b, the ventral orbital area, and the caudal secondary motor area. Rostral area 29b receives projections from caudal area 24a, whereas caudal area 29b receives projections from rostral area 24a. Area 29b also receives projections from area 24b and the ventral orbital area. Areas 29c and 29d receive projections from areas 24a and 24b and the secondary motor area in a topographic manner such that the rostrocaudal axis of areas 29c and 29d corresponds to the caudorostral axis of areas 24a and 24b and the secondary motor area. Rostral areas 29c and 29d also receive projections from the caudal primary motor area, and area 29d receives projections from the ventral, lateral, and medial orbital areas. These differential frontal cortical projections to each area of the retrosplenial cortex suggest that each area may contribute to different aspects of retrosplenial cortical function such as spatial memory and behavior.

Heterogeneous output pathways link the anterior pretectal nucleus with the zona incerta and the thalamus in rat

The anterior pretectal nucleus (APT) and the zona incerta (ZI) are diencephalic nuclei that exert a strong inhibitory influence selectively in higher order thalamic relays. The APT is also known to project to the ZI as well as the thalamus, but anatomical details of the APT-ZI projection have not been described. In the present study, the efferent pathways of the APT were examined in the APT-ZI-thalamus network by using anterograde and retrograde tracing in combination with pre- and postembedding immunocytochemical stainings and in situ hybridization. The vast majority of APT fibers selectively innervated the parvalbumin-positive, ventral part of the ZI, which contains ZI neurons with axons projecting to higher order thalamic nuclei. The APT-ZI pathway consisted of both gamma-aminobutyric acid (GABA)-negative and GABA-positive components; 38.2% of the terminals in the ZI contained GABA, and 8.6% of the projecting somata in the APT were glutamic acid decarboxylase 67 (GAD67) mRNA positive. The combination of parvalbumin immunostaining with retrograde tracing showed that strongly and weakly parvalbumin-positive as well as parvalbumin-negative neurons were all among the population of APT cells projecting to the ZI. Similar heterogeneity was found among the APT cells projecting to the thalamus. Double retrograde tracing from higher order thalamic nuclei and their topographically matched ZI regions revealed hardly any APT neuron with dual projections. Our data suggest that both ZI and the higher order thalamic relays are innervated by distinct, physiologically heterogeneous APT neurons. These various efferent pathways probably interact via the rich recurrent collaterals of the projecting APT cells. Therefore, the powerful, GABAergic APT and ZI outputs to the thalamus are apparently co-modulated in a synergistic manner via dual excitatory and inhibitory APT-ZI connections.

Recurrent laryngeal nerve post-natal development in rats

Studies on the normal pattern of development and post-natal maturation of the recurrent laryngeal nerve in rats are scanty. The aim of the present study was to investigate the normal microscopic aspects of the recurrent laryngeal nerve myelinated fibers in the post-natal developing rat, with special attention to longitudinal morphology and lateral symmetry. Fifteen male rats were divided into experimental groups according to age 20, 55, 76, 150 and 250 days. A female group aged between 76 and 150 days was also used. Right and left RLN were studied by light microscopy at proximal, medium and distal segments and morphometric data comparisons were made between sides, segments, ages and gender. Our results showed that the left recurrent laryngeal nerves were significantly longer than the right in all ages studied and this difference increased with ageing. There was a slight decrease in the myelinated fiber number, according to proximal to distal gradient, but a significant decrease was observed only on older animals (ages 55 (both sides), 76 (left side), and 150 (left side) days). This difference was also observed for female rats (left side). No differences between ages were observed. There was an age-dependent difference on ranges and histograms form (younger animals showed a unimodal histogram while older animals showed a bimodal one), with no significant differences between segments or sides, in all groups studied. Also, no differences between males and females of the same age were observed. In conclusion, the RLN alters its morphology due to development and ageing and the present study describe normal patterns of the recurrent laryngeal nerve development in rats that can be useful for a better understanding of pathological alterations on experimental neuropathies involving the laryngeal nerves.

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.

Surgical anatomy of the liver, hepatic vasculature and bile ducts in the rat

BACKGROUND

The rat is the most used experimental model in surgical research. Virtually all procedures in clinical liver surgery can be performed in the rat. However, the use of the rat model in liver surgery is limited by its small size and limited knowledge of the liver anatomy. As in humans, the rat liver vasculature and biliary system have many anatomical variations. The development of surgical techniques, and the study of liver function and diseases require detailed knowledge of the regional anatomy.

AIM

The objective of this study was to describe and illustrate systematically the surgical anatomy of the rat liver to facilitate the planning and performance of studies in this animal. Knowledge of the diameter and length of liver vessels is also important for the selection of catheters and perivascular devices.

METHODS

Twelve Wistar rat livers were dissected using a surgical microscope. Hepatic and extrahepatic anatomical structures were measured under magnification with a millimeter scale.

CONCLUSION

In this study, we describe the rat liver topographical anatomy, compare it with the human liver and review the literature. Increased knowledge of the rat liver anatomy and microsurgical skills permit individualized dissection, parenchymal section, embolization and ligature of vascular and biliary branches.

Immunohistochemical distribution of the secretogranin II-derived peptide EM66 in the rat hypothalamus: A comparative study with jerboa

EM66 is a 66-amino acid peptide derived from secretogranin II, a member of granin acidic secretory protein family, by proteolytic processing. EM66 has been previously characterized in the jerboa (Jaculus orientalis) hypothalamus and its potential implication in the neuroendocrine regulation of feeding behaviour has been demonstrated. In the present study, an immunohistochemical analysis of the localization of EM66 within hypothalamic structures of rat was performed and compared to the distribution of EM66 in the jerboa hypothalamus. In the rat hypothalamus, as in the jerboa, EM66 immunostaining was detected in the parvocellular paraventricular, preoptic and arcuate nuclei, as well as the lateral hypothalamus which displayed an important density of EM66-producing neurones. However, unlike jerboa, the suprachiasmatic and supraoptic nuclei of the rat hypothalamus were devoid of cellular EM66-immunolabeling. Thus, the novel peptide EM66 may exert common neuroendocrine activities in rat and jerboa, e.g. control of food intake, and species-specific roles in jerboa such as the regulation of biological rhythms and hydromineral homeostasis. These results suggest the existence of differences between jerboas and rats in neuroendocrine regulatory mechanisms involving EM66.

Microscopic anatomy of brachial plexus branches in Wistar rats

In the present study, we analyze the morphology and morphometry of the lateral proper digital nerve of the third finger, and of the proximal and distal segments of the ulnar, median, and radial nerves, in Wistar rats 4 or 7 weeks old. The fascicular area and diameter were generally significantly greater in the proximal compared to distal segments and tended to be larger in 7-week-old compared to 4-week-old rats (e.g., median nerve area of 0.13 mm(2) for the proximal and 0.07 mm(2) for distal segments in 4-week-old rats, and 0.17 and 0.10 mm(2), respectively, for the proximal and distal segments of 7-week-old rats). The number of fascicles was significantly greater while the number of myelinated fibers was significantly less in the distal segments (e.g., 1,359 and 509 myelinated fibers, respectively, in the proximal and distal segments of the radial nerve 4-week-old rats). There was no significant difference in these parameters between the two age groups. The diameter of the myelinated fibers and their respective axons increased from 4 to 7 weeks of age (e.g., myelinated fiber diameter of 4.10 microm in 4-week-old animals and 4.7 microm in the ulnar nerve proximal segment of 7-week-old rats). The g-ratio regression line (axon diameter vs. fiber diameter quotient) was outlined for all the nerves studied here. Differences in myelinated fiber density were detected between the segments of the radial nerve, accompanying the number of myelinated fibers. Detailed knowledge of the microscopic anatomy of rat forelimb nerves provides control data for comparison with studies of experimentally induced neuropathies, which can shed more light on human neuropathies.

Morphometrical Characteristics of Age-Associated Changes in the Thymus of Old Male Wistar Rats

In order to provide a morphometrical description of the changes in the aged rat thymus and to relate them to apoptotic and proliferative activity of thymocytes, the thymuses from 3- and 18-month-old male Wistar rats and the percentages of bromodeoxyuridine-incorporating and apoptotic cells in cultures of thymocytes were assessed by stereological analysis and flow cytometry, respectively. In old rats the volume of lymphoepithelial thymic tissue is markedly reduced, reflecting a sharp decrease in the total number of thymocytes. A reduction in the proliferative capacity of thymocytes and increase in their susceptibility to apoptosis are, most likely, primarily responsible for a 7-fold reduction in thymic cellularity in old animals. Furthermore, only the volume of cortical compartment was affected by aging, while that of medulla, despite of reduced cellularity, was not significantly altered. The loss of functional tissue in aged thymus is compensated by a substantial increase in the volume of inter-lobular connective and adipose tissue, so the thymic weight remained unaltered in old rats. These results suggest that thymus of aged Wistar rats exhibits morphological characteristics similar to those found in aged human thymus and thus may serve as an animal model for further investigations of thymus-related changes in immunological aging.

Some aspects of rat femorotibial joint microanatomy as demonstrated by high-resolution magnetic resonance imaging

High-resolution magnetic resonance images (MRI) of the right femorotibial joint of normal Han:Wistar rats were acquired using a 4.7 Tesla magnet and a single-turn solenoid radio frequency coil (built in-house). Some anatomical findings of the rat femorotibial joint, which have not been reported previously using MRI, are described. The separation of patellar ligament and crural fascia was feasible on MRI. This separation would not be seen on images of lower resolution and its presence on high-resolution images could be mistaken for artefact due to the magic angle effect. Band-like fibrous structures exist in the infra-patellar fat pad, which might be mistaken as ligaments within the femorotibial joint. On sagittal MRI a vessel was seen inserted on the central part of the caudal surface of the patellar ligament. Subcutaneous fascia/cutaneous muscles (panniculus carnosus) could also be demonstrated with MRI in the femorotibial joint area.

Changes in the number and distribution of myoepithelial cells in the rat parotid gland during postnatal development

The mature rat parotid gland shows hardly any cell bodies of myoepithelial cells around the acini, only a few cell processes being visible. However, in the early postnatal period, the rat parotid gland shows many myoepithelial cell bodies around the acini, including the intercalated ducts. In order to clarify the reason for the disappearance of myoepithelial cells from the area around the acinus during postnatal development, changes in the number and distribution of myoepithelial cells in the rat parotid gland were examined histochemically and chronologically, with particular reference to cell proliferation and cell death. From day 7 to day 14, many myoepithelial cells showing a positive reaction with anti-actin antiserum were found around the acini and intercalated ducts, but thereafter the number of such cells decreased gradually, particularly around the acini, and had almost disappeared after day 35. BrdU/PCNA-positive myoepithelial cells surrounding the acini were easily detected on day 14, but disappeared by day 21, whereas BrdU/PCNA-positive acinar cells remained numerous even after day 21. TUNEL/ISEL staining showed no positive myoepithelial cells throughout the observation period. Transmission electron microscopy also demonstrated no myoepithelial cells with chromatin condensation characteristic of apoptosis through the observation period. These findings suggest that the main reason for the disappearance of myoepithelial cells from the area around the acinus during postnatal development is the large difference between the number of myoepithelial cells and that of acinar cells, because the acinar cells retain their proliferative activity even after myoepithelial cells have become quiescent.

Brain stem afferent connections of the amygdala in the rat with special references to a projection from the parabigeminal nucleus: a fluorescent retrograde tracing study

A recently revealed important function of the amygdala (Am) is that it acts as the brain's "lighthouse", which constantly monitors the environment for stimuli which signal a threat to the organism. The data from patients with extensive lesions of the striate cortex indicate that "unseen" fearful and fear-conditioned faces elicit increased Am responses. Thus, also extrageniculostriate pathways are involved. A multisynaptic pathway from the retina to the Am via the superior colliculus (SC) and the pulvinar was recently suggested. We here present data based on retrograde neuronal labeling following injection of the fluorescent tracer Fluoro-Gold in the rat Am that the parabigeminal nucleus (Pbg) emits a substantial, bilateral projection to the Am. This small cholinergic nucleus (Ch8 group) in the midbrain tegmentum is a subcortical relay visual center that is reciprocally connected with the SC. We suggest the existence of a second extrageniculostriate multisynaptic connection to Am: retina-SC-Pbg-Am, that might be very effective since all tracts listed above are bilateral. In addition, we present hodological details on other brainstem afferent connections of the Am, some of which are only recently described, and some others that still remain equivocal. Following selective injections of Fluoro-Gold in the Am, retrogradely labeled neurons were observed in parasubthalamic nucleus, peripeduncular nucleus, periaqueductal gray, dopaminergic nuclear complex (substantia nigra pars lateralis and pars compacta, paranigral, parabrachial pigmented and interfascicular nuclei, rostral and caudal linear nuclei, retrorubral area), deep mesencephalic nucleus, serotoninergic structures (dorsal, median and pontine raphe nuclei), laterodorsal and pedunculopontine tegmental nuclei (Ch6 and Ch5 groups), parabrachial nuclear complex, locus coeruleus, nucleus incertus, ventrolateral pontine tegmentum (A5 group), dorsomedial medulla (nucleus of the solitary tract, A2 group), ventrolateral medulla (A1/C1 group), and pars caudalis of the spinal trigeminal nucleus. A bilateral labeling of the upper cervical spinal cord was also observed.

The urethral striated sphincter in adult male rat

This study reports the morphology of the urethral sphincter in adult male rats, mainly the histological aspects, the features of the endplates, and the heavy myosin chain distribution in the striated fibres. First, the prostate is entirely out of the striated sphincter, which is surprising when compared to man. Second, the urethral striated sphincter consists of two lateral fascicles separated by an anterior and a posterior strip of connective tissue, which extend from the prostatic urethra (i.e. the part of the urethra which runs though the prostate) to the bulb of the penis. An additional third fascicle of striated muscle (SM) covers the caudal part of the anterior connective strip of the membranous urethra (i.e. the urethra which extends from its prostatic part to the bulb of the penis). In the membranous urethra, the striated sphincter surrounds directly the urethral lumen without intercalated smooth muscle. In urethral cross sections, the endplates detected by alpha-bungarotoxin, which binds to nicotinic receptors, are clustered in the postero-lateral part of the lateral fascicles. The cross-sectional area of the urethral striated fibres shows a bimodal distribution: the largest fibres are located at the periphery of the sphincter and these fibres express only fast myosin heavy chains (MHC) as shown by immunochemistry. The smallest fibres are less numerous and are situated near the lumen co-expressing fast and slow MHC. All the striated fibres express desmin and dystrophin as SM fibres do. Taken together, these results suggest that the urethral striated fibres in male rat present the same characteristics as those of the skeletal muscles. The predominance of fast fibres is consistent with phasic contractions playing a role not only during micturition and urinary continence but also probably during ejaculation.

Androgen-dependent morphology of prostates and seminal vesicles in the Hershberger Assay: Evaluation of immunohistochemical and morphometric parameters

The aim of this study was to evaluate androgen-like effects using immunohistochemical and morphometric methods. Therefore, orchiectomized Wistar rats (n > or = 13) were treated s.c. with 1 mg/kg bw/day testosterone propionate (TP) for 7 days and compared to orchiectomized rats without TP substitution (OX) and to an untreated intact control group. Sections obtained from prostates and seminal vesicles were stained with polyclonal and monoclonal antibodies against the androgen receptor (AR) and assessed densitometrically (intensity of the immunoreaction) and morphometrically (epithelial height, luminal area). TP caused an enhancement of staining intensity and an increase in organ weights, epithelial height and luminal area. The use of proliferation markers (PCNA, MIB-5) showed also a highly significant increase of immunoreactive cells in TP-substituted orchiectomized rats compared with the OX group. Based on the present data, the densitometric analysis of AR-immunoreactivity as well as the assessment of proliferation markers, epithelial height and luminal area proved to be sensitive parameters for the evaluation of androgen effects on prostates and seminal vesicles. In further studies these parameters will be used to test several industrial xenooestrogens as well as phytooestrogens on their possible androgenic capacity.

Noradrenergic innervation of the developing and mature septal area of the rat

The noradrenergic innervation of the developing and mature septal area of the rat was examined with light and electron microscopic immunocytochemistry using an antibody against dopamine-beta-hydroxylase. At birth, a small number of relatively thick noradrenergic fibers were found to innervate the lateral septum (mainly its intermediate part) and the nuclei of the vertical and horizontal limbs of the diagonal band of Broca. By postnatal day 7, a substantial increase in their density was observed. At this age some labeled fibers left the medial forebrain bundle and invaded the nucleus of the horizontal limb of the diagonal band. These fibers then ran in a ventrodorsal direction and innervated the nucleus of the vertical limb before entering the medial septum. Immunoreactive fibers were finer and more varicose than at birth. In the subsequent 2 weeks, the density of labeled fibers in the septal area was further increased. By postnatal day 21, the distribution pattern and density of the noradrenergic innervation appeared similar to the adult. In the adult, noradrenergic fibers exhibited more varicosities than in younger rats. Electron microscopic analysis revealed a low proportion (peaked at P7) of noradrenergic varicosities engaged in synaptic contacts throughout development. The overwhelming majority of these synapses were symmetrical, predominantly with small or medium-sized dendrites. The present findings provide the morphological basis for the functional interactions between noradrenergic afferents and neuronal elements in the septal area. The low proportion of synaptic contacts found in this study suggests that noradrenaline may exert its action in the septal area mainly through transmission by diffusion (volume transmission), as has been suggested for other areas of the developing and adult brain.

Successive depth variations in microvascular distribution of rat somatosensory cortex

Although hemodynamic-based functional brain imaging techniques are powerful tools to explore the brain functions noninvasively, hemodynamic-based signal is strongly affected by spatial configuration of microvessels. Understanding the quantitative relations between microvascular structure and functional activity is therefore significant to make a valid signal interpretation for the imaging techniques. In the present study, we evaluated depth profiles of microvascular distributions in rat somatosensory subfields (barrel field, forelimb region, trunk region and hindlimb region) and characterized depth variations in microvascular structures, such as locations, lengths and directions of microvessels, throughout the cortical layers (I-VI). To obtain the accurate microvascular structure, we made a customized casting method by using confocal laser scanning microscope. We observed that microvascular distribution successively varied throughout the cortical layers (I-VI) and that the maximum number density of microvessels was consistently found in middle layers (III-V). In addition, superficial layers had relatively long microvessels, almost perpendicular to the cortical surface, whereas middle layers had short microvessels propagating in all directions. These regional differences in microvascular structures were closely related to the somatosensory subfields, e.g., barrel field was the greatest number density of microvessels among the investigated subfields. Based on these observations, we compared microvascular profiles with previously reported distribution patterns of tissue partial pressure of oxygen (pO2). The results showed that tissue pO2 was correlated with microvascular distribution in some but not all of the subfields. This finding shows that detailed microvascular profiles are helpful to investigate causal relationships between microvascular structure and functional activities in cerebral cortex.

Mechanical properties of rat soleus aponeurosis and tendon during variable recruitment in situ

The in vitro mechanical properties of tendons are well described, whereas little data exist for conditions mimicking those found in vivo. Descriptions of the in situ mechanical properties of aponeuroses are more common, but the results are variable. Our goal was to examine the mechanical properties of these tissues under conditions mimicking the in vivo state. Tissue strains were measured in the rat (Rattus norvegicus) soleus muscle directly from the spacing of metal markers implanted within the tissues of interest using an X-ray video microscope. Strains were measured for the tendon and three regions (proximal, middle and distal) of the aponeurosis. Muscle stimulation was accomplished through isolated ventral rootlets, allowing force to be graded in seven repeatable increments independent of muscle-tendon unit length. Peak strains (during maximal tetanic contraction at optimum length; P(o)) were approximately 5% in tendon and approximately 12% in all regions of the aponeurosis. At forces above 50% of P(o), tissue stiffness was nearly constant in all regions, and a pronounced toe region was observed only at forces below approximately 25% of P(o). Stiffness increased in all regions as the muscle-tendon unit was lengthened. These results suggest that using mechanical properties measured ex vivo or during single contractile events in situ to estimate the in vivo behavior of tendon and aponeurosis may lead to errors in estimating the distribution of strain among the contractile and series elastic elements of the muscle.

The striated urethral sphincter in female rats

The aim of this study was to give a microscopic description of the organization, the innervation and the slow or fast type of the striated fibers of the external urethral sphincter in the female rat. Conventional methods for photonic microscopy and immunochemistry were applied to cross and longitudinal sections of snap-frozen urethra. With hematoxylin-eosin stained cross sections, striated fibers are of small diameter and attached directly to the surrounding connective tissue. They are innervated by cholinergic endplates as shown by acetylcholinesterase techniques and alpha-bungarotoxin binding. The histological aspects of the cross sections as well as the distribution of endplates along the length of the sphincter suggest an organization of the fibers in four bundles, possibly acting as a photographic diaphragm does. Like striated skeletal muscle fibers, the fibers bind monoclonal antibodies against dystrophin with subsarcolemmal distribution and against desmin which visualizes striations. All the fibers express fast myosin heavy chains and very few co-express slow myosin heavy chains as determined by immunocytochemistry. We are taking advantage of the diaphragmatic organization of the striated sphincter to develop a longitudinal section as a model of chronic incontinence to test the efficiency of grafted myoblasts provided by fast striated skeletal muscle.

Histochemical study of innervation and NADPH-D activity of the thymus

Acetylcholinesterase (ACHE)-positive nerve fibres in the thymus of the rat form perivascular plexuses as well as free ACHE-positive nerves, which do not follow the course of the vessels. A higher number of ACHE-positive nerves was observed in corticomedullary border and the medulla, a lower number in the cortex of the thymus lobuli. A gradual reduction of ACHE-positive intrathymus nerve formation was recorded and correlated with the increasing age of the rats. Nicotinamide adenine dinucleotide phosphate-diaphorase positive cells observed in the rat thymus were irregular with numerous projections and were located on the boundary of the cortex and medulla.

Melatonin induces Cry1 expression in the pars tuberalis of the rat

In mammals, interacting transcriptional/post-translational feedback loops involving 'clock genes' and their protein products control circadian organisation. These genes are not only expressed in the master circadian clock of the suprachiasmatic nuclei (SCN) but also in many peripheral tissues where they exhibit similar but not identical dynamic to that seen in the SCN. Among these peripheral tissues, the pars tuberalis (PT) of the pituitary expresses clock genes. We show here that the PT of the rat, like that of other rodents, rhythmically expresses Per1. We also report rhythmic expression of another clock gene, Cry1. The peak of Cry1 mRNA expression occurs during the night concomitantly with rising blood plasma melatonin concentrations. Using an acute injection paradigm, we demonstrate that Cry1 expression is directly induced by melatonin in the PT. Melatonin injection at the end of the subjective day also affects Per1 expression, leading to diminished mRNA levels. These data support the existence of a time-measurement model in the PT based on direct opposite actions of melatonin on Per1 and Cry1 expression.

Compartmental fasciotomy and isolating a muscle from neighboring muscles interfere with myofascial force transmission within the rat anterior crural compartment

Muscles within the anterior crural compartment (extensor digitorum longus, EDL; tibialis anterior, TA; and extensor hallucis longus, EHL) and within the peroneal compartment were excited simultaneously and maximally. All muscles were kept at constant length with the exception of EDL, for which muscle length was changed by moving its proximal tendon. Active and passive force was measured at proximal as well as distal EDL tendons and at the combined distal tendons of TA and EHL (TA+EHL). In the initial experimental condition, a difference (F(proximal) > F(distal)) in EDL force, amounting to 0-14% of proximal force, was confirmed for most EDL lengths. This is interpreted as a clear proof of extramuscular myofascial force transmission, as no significant EDL length effects could be shown on TA+EHL force. Repeated measurements were confirmed to cause marked changes of both proximal and distal length-force characteristics, such as a shift of the whole ascending limb of the active curve, including optimum length, to higher lengths without decreasing optimum force, and decreasing active force at low lengths (by approximately 57%). Repeated measurements also lowered proximal and distal EDL passive force (by up to 35%). The proximo-distal difference in passive as well as active EDL force was decreased, but persisted. At most lengths, this difference for active force amounted to a constant fraction (14%) of proximal force. TA+EHL force was not affected significantly. Subsequently, acute effects of experimental surgical alterations were studied: The first manipulation was full lateral fasciotomy of the anterior crural compartment that caused a further decrease in active force at the proximal EDL but not at the distal EDL tendon. Passive forces showed no further significant changes. The proximo-distal EDL active force difference decreased to 0-5% of proximal force. After fasciotomy, TA+EHL force increased by 30%. This was interpreted as evidence of increased intramuscular and decreased extramuscular myofascial force transmission. The second manipulation was full isolation of EDL from TA+EHL, but not from extramuscular connective tissues, which caused a further decrease of the EDL proximo-distal force differences, indicating a stiffening effect of the presence of TA+EHL on the extramuscular matrix. For EDL active force the difference was no longer significantly different from zero. In contrast, for EDL passive force the proximo-distal force difference persisted. It is concluded that extramuscular myofascial force transmission is an important feature of the anterior crural compartment. The magnitude of this force transmission requires that it be considered in analysis of muscular function.

Migration of erythroblastic islands toward the sinusoid as erythroid maturation proceeds in rat bone marrow

It has been hitherto considered that mature erythroblasts migrate toward the sinusoid along the cytoplasmic processes of macrophages of erythroblastic islands in bone marrow. Our previous report, however, has demonstrated the morphological features of a mature erythroblastic island passing through the sinusoidal endothelium. In this study, the possibility of migration of erythroblastic islands toward the sinusoid was examined in rat bone marrow by light microscopical histoplanimetry. As a result, the more mature erythroblasts were not regularly arranged in the peripheral direction of the erythroblastic islands. Immature erythroblasts were populated more in the erythroblastic islands away from the sinusoid than in those islands neighboring the sinusoid, whereas mature erythroblasts were more in erythroblastic islands neighboring the sinusoid. These findings suggest that the formation of erythroblastic islands occurs in a region away from the sinusoid, and that erythroblastic islands migrate towards the sinusoids as erythroid maturation proceeds.

Immunohistochemical localization of chromogranin a in the acinar cells of equine salivary glands contrasts with rodent glands

We investigated the existence of chromogranin A (CgA) in salivary glands of the horse by Western blotting and enzyme immunoassay (EIA) using an antiserum against a peptide sequence of equine CgA. We also compared its cellular distribution between the horse and rat salivary glands with a tyramide signal amplification immunofluorescence technique. Western blotting gave three significant immunoreactive bands (74, 56 and 48 kDa) in adrenal medulla and three major salivary glands of horses. Immunoreactivities for CgA measured by EIA in horses were 154.05 +/- 41.46, 20.32 +/- 5.59 and 4.43 +/- 2.23 pmol/g wet weight in the parotid gland, submandibular gland and sublingual gland, respectively, and 1.03 +/- 0.407 pmol/mg protein in the saliva. Immunohistochemically, the positive reactivity was mainly recognized at acinar cells in equine salivary glands. This exhibits a contrast to the finding in the rat salivary glands that the CgA immunoreactivity is localized at the duct cells of the submandibular gland. These results provide novel evidence that in the horse, CgA is stored in the acinar cells of salivary glands, and secreted into saliva.

Alcohol effects on the principal and clear cells of the caput epididymis of albino rats

Ultrastructural observations of principal cells of the epithelium lining of the proximal caput epididymis in experimental alcoholic albino rats at 180 days of treatment showed pyknotic nuclei, ill-defined cellular organelles and clusters of electrondense bodies, perhaps lysosomes. It was also verified for a progressive accumulation of lipid droplets initially in the basal and perinuclear cytoplasm and finally in the apical cytoplasm of principal cells at 60, 120 and 180 days of experimentation, respectively. The clear cells of alcoholic rats at 180 days showed the cytoplasm totally filled with lipid droplets. These findings were taken comparatively with the morphological features of the same epididymal cells in control (normal) rats.

Motion of the foot and ankle during the stance phase in rats

Computerized analysis of rat gait is becoming an invaluable technique used by some peripheral nerve investigators for the evaluation of function. In this article we describe the use of a biomechanical model of the foot and ankle that allows a quantitative assessment and description of the ankle angle, reflecting plantarflexion and dorsiflexion during the stance phase of gait. Kinematic data of 144 trial walks from 36 normal rats were recorded with a high-speed digital image camera at 225 images per second. The ankle angular changes associated with the specific temporal events of foot placement on the ground through the stance phase were assessed. The information obtained was used to propose a new subdivision of the stance phase in the rat into three major components. This approach will provide a helpful research tool to analyze gait data that rely on the accurate determination of spatiotemporal foot events.

Residential maze as a task for testing rats' maze learning ability: effects of hippocampal lesions and cholinergic receptor antagonists

We investigated whether rats can learn mazes by a procedure in which rats were left in the maze (residential maze) in groups for 1 h a day. Water and food locations, which served as the start and goal boxes respectively in the test trial, were at the opposite ends of the maze. On the test trial conducted everyday before the residence period, animals put in the start box showed a significant decrease of the error response into the blind alleys and running time to reach the goal box. Systemic administration of scopolamine (0.25, 0.5 mg/kg), a muscarinic receptor antagonist, dose-dependently increased the number of errors, but mecamylamine, a nicotinic receptor antagonist, had no effect. Bilateral hippocampal lesions retarded both the acquisition and retention of this maze learning. The results suggest that this residential maze procedure is useful for testing maze learning ability in rats.

Phenotype of Per1- and Per2- expressing neurons in the suprachiasmatic nucleus of a diurnal rodent ( Arvicanthis ansorgei ): comparison with a nocturnal species, the rat

In mammals, the suprachiasmatic nuclei (SCN) are the site of the master circadian pacemaker whose molecular core mechanism is based on interlocking transcriptional/translational feedback loops involving clock genes. Among clock genes, Per1 and Per2 are important for both the maintenance of circadian rhythmicity and entrainment to light cues. Several circadian rhythms (e.g., locomotor activity) present opposite patterns in diurnal and nocturnal species. To test whether a differential cellular expression of clock genes in the SCN could constitute the neural substrate leading to diurnal or nocturnal behavior, we identified, by single or double non-radioactive hybridizations, the phenotype of neurons expressing Per1 and Per2 during the day in a diurnal species, Arvicanthis ansorgei, and in a nocturnal species, the rat (Rattus norvegicus). We show that in both species, expression of Per1 and Per2 is mostly restricted to the dorsomedial part of the SCN, often coexpressed with arginine vasopressin (AVP). A few vasoactive intestinal polypeptide (VIP) neurons were also shown to express Per1 and Per2. This differential expression of Per1 and Per2 in AVP and VIP neurons is more distinct in A. ansorgei than in the rat. Thus, our data suggest a major role for the dorsomedial part of the SCN in the maintenance of circadian rhythmicity. Furthermore, the similar diurnal pattern of Per1 and Per2 expression in diurnal and nocturnal rodents suggests that the circadian organization of locomotor activity rhythms probably relies on differential cellular integration mechanisms downstream of the clock.

Projections from the amygdaloid complex to the claustrum and the endopiriform nucleus: a Phaseolus vulgaris leucoagglutinin study in the rat

The claustrum and the endopiriform nucleus contribute to the spread of epileptiform activity from the amygdala to other brain areas. Data of the distribution of pathways underlying the information flow between these regions are, however, incomplete and controversial. To investigate the projections from the amygdala to the claustrum and the endopiriform nucleus, we injected the anterograde tracer Phaseolus vulgaris leucoagglutinin into various divisions of the amygdaloid complex, including the lateral, basal, accessory basal, central, anterior cortical and posterior cortical nuclei, the periamygdaloid cortex, and the amygdalohippocampal area in the rat. Analysis of immunohistochemically processed sections reveal that the heaviest projections to the claustrum originate in the magnocellular division of the basal nucleus. The projection is moderate in density and mainly terminates in the dorsal aspect of the anterior part of the claustrum. Light projections from the parvicellular and intermediate divisions of the basal nucleus terminate in the same region, whereas light projections from the accessory basal nucleus and the lateral division of the amygdalohippocampal area innervate the caudal part of the claustrum. The most substantial projections from the amygdala to the endopiriform nucleus originate in the lateral division of the amygdalohippocampal area. These projections terminate in the central and caudal parts of the endopiriform nucleus. Lighter projections originate in the anterior and posterior cortical nuclei, the periamygdaloid cortex, the medial division of the amygdalohippocampal area, and the accessory basal nucleus. These data provide an anatomic basis for recent functional studies demonstrating that the claustrum and the endopiriform nucleus are strategically located to synchronize and spread epileptiform activity from the amygdala to the other brain regions. These topographically organized pathways also provide a route by means of which the claustrum and the endopiriform nucleus have access to inputs from the amygdaloid networks that process emotionally significant information.

Neonatal development of projections to the basolateral amygdala from prefrontal and thalamic structures in rat

Recently an animal model for neurodevelopmental disorders has been developed. In this model the effects of an early neonatal [postnatal day 7 (Pd7)] basolateral amygdala lesion are compared with the effects of a lesion later in life (Pd21). Early amygdala damage results in enduring behavioral disturbances that become more manifest after puberty. These disturbances were not present in animals lesioned at Pd21. Accordingly it was postulated that the early damage may affect the neuroanatomical and neurochemical organization and functioning of other brain structures. To obtain information on the innervation of the amygdala during normal development, we used the retrograde tracer fluoro-gold. From neonatal day 7 onward (studied until Pd19), retrogradely labeled cells were present in the caudal and rostral thalamus, the substantia innominata, and the prefrontal but not the caudal cortex. Development of the topography of the projecting cells differed substantially for the thalamic regions and substantia innominata vs. the cortical regions. In thalamic regions and substantia innominata, no changes were observed during the studied period (Pd7-Pd9). In the prefrontal cortex, the number of labeled cells increased (from Pd7 to Pd13), the topography of the location of the cells changed from unilateral to bilaminar (from Pd9 to Pd13), and the number of subareas in which the cells were present increased (from Pd7 to Pd13). In the caudal cortex, relatively few cells were present up to Pd15. From Pd17 onward, a bilaminar topography of the location of the cells was observed. These data provide information on the circuitry that may be involved in the aberrant neurodevelopment of neonatally amygdala-lesioned rats, which has been proposed as an animal model for neurodevelopmental psychopathological disorders.

Projection patterns of commissural interneurons in the lumbar spinal cord of the neonatal rat

We have studied the axonal projection patterns of commissural interneurons (CINs) in the neonatal rat spinal cord. Some CINs are integral components of the neuronal networks in the vertebrate spinal cord that generate locomotor activity. By using differential retrograde labeling protocols with fluorescent dextran amines, we show that CINs with ascending axons (ascending CINs, or aCINs) and CINs with descending axons (descending CINs, or dCINs) constitute largely different populations. We show that aCINs and dCINs occupy partially overlapping domains in the transverse plane. The aCINs are located at the dorsal margin, within the dorsal horn, centrally within the intermediate zone, and in the medial region of the ventral horn, whereas the dCINs are located predominantly among the ventral and central aCINs and in smaller numbers within the dorsal horn. The labeled aCINs and dCINs project for at least one and a half segment rostrally or caudally and are present in roughly equal numbers. We also demonstrate the presence of a third, smaller population of CINs whose axons bifurcate to project for at least one and a half segment both rostrally and caudally (adCINs). The adCINs are located predominantly among the central and ventral groups of aCINs and dCINs. Finally, we demonstrate the presence of CINs with axons projecting for fewer than one and a half segment in either direction. These "short-range CINs" are intermingled with the aCINs, dCINs, and adCINs. Our results provide an anatomical framework for further electrophysiological studies aimed at identifying the CINs that participate in the mammalian locomotor central pattern generator.

Hippocampal and prefrontal cortical inputs monosynaptically converge with individual projection neurons of the nucleus accumbens

Afferents to the nucleus accumbens from different sources innervate specific areas of the central "core" and peripheral "shell" and are related to each other, at the light microscopical level, in an intricate overlapping and nonoverlapping way. This lack of homogeneity suggests that this region consists of circuits involving emsembles of neurons modulated by specific sets of convergent afferent inputs and abnormal regulation of such ensembles has been implicated in mental disorders. Early extracellular studies suggested that individual Acb neurons might respond to activation of afferents from more than one excitatory input: More recent studies of hippocampal and amygdalar or prefrontal cortical afferents suggest that hippocampal afferents gate the input from the prefrontal cortex or amygdala. Electrophysiological evidence for convergence of excitatory afferents in the Acb is strong and suggests that these pathways are monosynaptic. Nevertheless, this convergence has proved difficult to demonstrate anatomically as a result of the spatial distribution of the afferent inputs on the dendritic tree of the target neurons. To establish whether individual accumbens neurons receive monosynaptic input from pairs of afferents, one projection was labelled anterogradely with Phaseolus vulgaris leucoagglutinin and the second with biotinylated dextran amine (BDA) with Vector slate grey and 3,3'-diaminobenzidine tetrahydrochloride as the chromagens. Accumbens neurons possibly postsynaptic to these afferents, labelled by an in vivo focal injection of BDA, were examined using correlated light and electron microscopy to establish the proximal-distal distribution of labelled afferent synaptic inputs on their dendritic arbours. Individual cells were shown to receive monosynaptic afferent input from both ventral subiculum and prefrontal cortex, providing an anatomical framework for the hippocampal gating of other limbic inputs to the accumbens.

A quantitative morphometric analysis of rat spinal cord remyelination following transplantation of allogenic Schwann cells

Quantitative morphometric techniques were used to assess the extent and pattern of remyelination produced by transplanting allogenic Schwann cells into demyelinated lesions in adult rat spinal cords. The effects of donor age, prior culturing of donor cells, prior lesioning of donor nerves, and host immunosuppression were evaluated by transplanting suspensions of 30,000 acutely dissociated or cultured Schwann cells from neonatal, young adult, or aged adult rat sciatic nerves into X-irradiation and ethidium bromide-induced demyelinated dorsal column lesions, with or without co-transplantation of neonatal optic nerve astrocytes. Three weeks after transplantation, spinal cords were processed for histological analysis. Under all Schwann cell transplant protocols, large areas containing many Schwann cell-like myelinated axon profiles could be readily observed throughout most of the lesion length. Within these "myelin-rich" regions, the vast majority of detectable axons showed a peripheral-like pattern of myelination. However, interaxonal spacing also increased, resulting in densities of myelinated axons that were more similar to peripheral nerve than intact dorsal columns. Freshly isolated Schwann cells remyelinated more axonal length than cultured Schwann cells, and cells from younger donors remyelinated slightly more axon length than cells from older donors, but all Schwann cell transplant protocols remyelinated tens of thousands of millimeters of axon length and remyelinated axons at similar densities. These results indicate that Schwann cells prepared under a variety of conditions are capable of eliciting remyelination, but that the density of remyelinated axons is much lower than the myelinated axon density in intact spinal cords.

Effects of oxygen and glucose deprivation on the expression and distribution of neuronal and inducible nitric oxide synthases and on protein nitration in rat cerebral cortex

Changes in the nitric oxide (NO) system of the rat cerebral cortex were investigated by immunohistochemistry, immunoblotting, NO synthase (NOS) activity assay, and magnetic resonance imaging (MRI) in an experimental model of global cerebral ischemia and reperfusion. Brains were perfused transcardially with an oxygenated plasma substitute and subjected to 30 minutes of oxygen and glucose deprivation, followed by reperfusion for up to 12 hours with oxygenated medium containing glucose. A sham group was perfused without oxygen or glucose deprivation, and a further group was treated with the NOS inhibitor N(omega)-nitro-L-arginine methyl ester (L-NAME) before and during perfusion. Global ischemia led to cerebrocortical injury as shown by diffusion MRI. This was accompanied by increasing morphologic changes in the large type I interneurons expressing neuronal NOS (nNOS) and the appearance of nNOS immunoreactivity in small type II neurons. The nNOS-immunoreactive band and calcium-dependent NOS activity showed an initial increase, followed by a fall after 6 hours of reperfusion. Inducible NOS immunoreactivity appeared in neurons, especially pyramidal cells of layers IV-V, after 4 hours of reperfusion, with corresponding changes on immunoblotting and in calcium-independent NOS activity. Immunoreactive protein nitrotyrosine, present in the nuclear area of neurons in nonperfused controls and sham-perfused animals, showed changes in intensity and distribution, appearing in the neuronal processes during the reperfusion period. Prior and concurrent L-NAME administration blocked the changes on diffusion MRI and attenuated the morphologic changes, suggesting that NO and consequent peroxynitrite formation during ischemia-reperfusion contributes to cerebral injury.

Neonatal development of projections from the basolateral amygdala to prefrontal, striatal, and thalamic structures in the rat

Recently, an animal model for neurodevelopmental disorders has been developed. In this model, the effects of an early neonatal (postnatal day 7 [Pd 7]) basolateral amygdala lesion are compared with the effects of a lesion later in life (Pd 21). The reported data indicate that amygdala damage at a specific point early in life results in enduring behavioral disturbances that become more manifest after puberty, for example, only an early lesion resulted in a disruption of the prepulse inhibition, which is also observed in people suffering from schizophrenia. Accordingly, it was postulated that the early damage may affect the neuroanatomic and neurochemical organization and functioning of other brain structures. This was studied by use of the anterograde tracers biotinylated dextran amine and Phaseolus vulgaris-leucoagglutinin. At neonatal days 7, 9, 11, 13, and 26, amygdaloid fibers were in particular present in the mediodorsal thalamus (MDT), nucleus accumbens (Acb), and prefrontal cortex (PFC). The development of the topography of the amygdaloid innervation, however, differed markedly for the MDT and Acb compared with the PFC. For the MDT and Acb, no major changes in innervation were observed between Pd 7 and Pd 26, whereas the innervation of the PFC reorganized from a neonatal diffuse (Pd 7 and 9) to a restricted pattern (Pd 11, 13, and 26). In addition, the innervation changed to an adult-like bilaminar pattern. These data provide information on the circuitry that may be involved in the aberrant neurodevelopment of neonatally amygdala-lesioned rats, which have been proposed as an animal model for neurodevelopmental psychopathological disorders.

Re-examination of the thalamostriatal projections in the rat with retrograde tracers

Topographical arrangements of thalamostriatal projection neurons was examined in the rat by the retrograde tract-tracing method. After injecting Fluoro-Gold (FG) and/or cholera toxin beta-subunit (CTB) in different regions of the caudate-putamen (CPu), distribution of retrogradely labeled neurons was observed in the thalamus. The main findings were as follows: (1) Retrogradely labeled neurons were seen in the midline-intralaminar thalamic nuclei in all rats examined in the present study. Neurons in the ventral lateral and posterior thalamic nuclear groups were also labeled in the rats which were injected with the tracer into the dorsal part of Cpu, but not in the rats which were injected with the tracer into the nucleus accumbens (Acb) and its adjavent regions in the ventromedial part of the Cpu. (2) Topographical organization was observed in the projections from the midline-intralaminar thalamic nuclei to the CPu. After the tracer injection into the dorsal part of the CPu or the ventral part of the CPu (including the Acb), labeled neurons in the midline-intralaminar thalamic nuclei were distributed predominantly in the lateral part of the intralaminar nuclei or the midline nuclei, respectively. On the other hand, after the tracer injection into the medial or the lateral part of the CPu, labeled neurons in the midline-intralaminar nuclei were distributed mainly in the dorsal or the ventral part of these nuclei, respectively. (3) Topographical organization was also observed in the thalamostriatal projections from the ventral and Pos. After the tracer injection into the rostral part of the CPu, labeled neurons were distributed mainly in the rostral part of the ventral nuclear group. On the other hand, after the tracer injection into the caudal part of the CPu, labeled neurons were distributed mainly in the caudal part of the ventral nuclear group, as well as in the posterior nuclear group.

The distribution of cannabinoid-induced Fos expression in rat brain: differences between the Lewis and Wistar strain

Previous studies have suggested that cannabis-like drugs produce mainly aversive and anxiogenic effects in Wistar strain rats, but rewarding effects in Lewis strain rats. In the present study we compared Fos expression, body temperature effects and behavioral effects elicited by the cannabinoid CB(1) receptor agonist CP 55,940 in Lewis and Wistar rats. Both a moderate (50 microg/kg) and a high (250 microg/kg) dose level were used. The 250 microg/kg dose caused locomotor suppression, hypothermia and catalepsy in both strains, but with a significantly greater effect in Wistar rats. The 50 microg/kg dose provoked moderate hypothermia and locomotor suppression but in Wistar rats only. CP 55,940 caused significant Fos immunoreactivity in 24 out of 33 brain regions examined. The most dense expression was seen in the paraventricular nucleus of the hypothalamus, the islands of Calleja, the lateral septum (ventral), the central nucleus of the amygdala, the bed nucleus of the stria terminalis (lateral division) and the ventrolateral periaqueductal gray. Despite having a similar distribution of CP 55,940-induced Fos expression, Lewis rats showed less overall Fos expression than Wistars in nearly every brain region counted. This held equally true for anxiety-related brain structures (e.g. central nucleus of the amygdala, periaqueductal gray and the paraventricular nucleus of the hypothalamus) and reward-related sites (nucleus accumbens and pedunculopontine tegmental nucleus). In a further experiment, Wistar rats and Lewis rats did not differ in the amount of Fos immunoreactivity produced by cocaine (15 mg/kg). These results indicate that Lewis rats are less sensitive to the behavioral, physiological and neural effects of cannabinoids. The exact mechanism underlying this subsensitivity requires further investigation.

Postnatal growth of the rat palatine gland

To elucidate how the palatine glands grow postnatally, the palatine glands of rats from 0 to 8 weeks of age were investigated histologically and immunohistochemically. Under light microscope, three dimensions of the right part of the palatine glands were measured and the total number of excretory ducts of the glands was counted from the parasagittal serial sections. Immunohistochemistry with anti-5-bromo-2'-deoxyuridine (BrdU) monoclonal antibody was also employed to detect the cellular proliferative activity. At birth (0 weeks), the palatine glands consisted of ducts and immature acini. The ducts in the glands were connected with excretory ducts. After 2 weeks, there was no duct in the glands. Most acinar cells became mature as mucous cells and took the form of tubulo-acini connected directly with excretory ducts. In the posterior region of the glands, serous acinar cells forming demilunes were occasionally seen. All three dimensions of the palatine glands became longer, and the number of excretory ducts tended to increase. Immunohistochemistry showed acinar and duct cells were highly proliferative in early stage of postnatal life and their proliferative activity decreased thereafter. This study demonstrated that immature rat palatine glands of newborn rats grow three-dimensionally during maturation, and that the parenchymal cell proliferation contributes to the growth of the rat palatine glands. In addition, it is suggested that the glandular tissue arises from the excretory ducts formed postnatally.

Regional differences in innervation of lymph nodes in the Wistar rat

Previous light microscopic investigations have indicated that, in the rat, the innervation of mesenteric lymph nodes may be less dense than that of axillary nodes. However, nerves of the enteric system are difficult to visualise by light microscopy. Therefore we quantified the density of innervation of axillary and mesenteric lymph nodes at the ultrastructural level. The results show a highly significant difference in the density of innervation between these 2 groups of lymph nodes, but morphologically the type of the innervation does not seem to differ. In previous studies, nerves were found predominantly in regions characterised by aggregations of plasma cells. In view of this association, we suggest that the difference in innervation may reflect the migration of plasma cells out of mesenteric nodes and into the mucosa of the gut wall. By contrast, in peripherally located nodes, plasma cells tend to remain within the lymph nodes, and hence the density of innervation of these nodes is greater.

The ubiquitin-proteasome cascade is required for mammalian long-term memory formation

It has been recently demonstrated that ubiquitin-proteasome-mediated proteolysis is required for long-term synaptic facilitation in Aplysia. Here we show that the hippocampal blockade of this proteolytic pathway is also required for the formation of long-term memory in the rat. Bilateral infusion of lactacystin, a specific proteasome inhibitor, to the CA1 region caused full retrograde amnesia for a one-trial inhibitory avoidance learning when given 1, 4 or 7h, but not 10 h, after training. Proteasome inhibitor I produced similar effects. In addition, inhibitory avoidance training resulted in an increased ubiquitination and 26S proteasome proteolytic activity and a decrease in the levels of IkappaB, a substrate of the ubiquitin-proteasome cascade, in hippocampus 4 h after training. Together, these findings indicate that the ubiquitin-proteasome cascade is crucial for the establishment of LTM in the behaving animal.

Localization of the presynaptic cytomatrix protein Piccolo at ribbon and conventional synapses in the rat retina: comparison with Bassoon

In recent years significant progress has been made in the elucidation of the molecular assembly of the postsynaptic density at synapses, whereas little is known as yet about the components of the presynaptic active zone. Piccolo and Bassoon, two structurally related presynaptic cytomatrix proteins, are highly concentrated at the active zones of both excitatory and inhibitory synapses in rat brain. In this study we used immunocytochemistry to examine the cellular and ultrastructural localization of Piccolo at synapses in the rat retina and compared it with that of Bassoon. Both proteins showed strong punctate immunofluorescence in the outer and the inner plexiform layers of the retina. They were found presynaptically at glutamatergic ribbon synapses and at conventional GABAergic and glycinergic synapses. Although the two proteins were coexpressed at all photoreceptor ribbon synapses and at some conventional amacrine cell synapses, at bipolar cell ribbon synapses only Piccolo was present. Our data demonstrate similarities but also differences in the molecular composition of the presynaptic apparatuses of the synapses in the retina, differences that may account for the functional differences observed between the ribbon and the conventional amacrine cell synapses and between the photoreceptor and the bipolar cell ribbon synapses in the retina.

Prepro-thyrotropin releasing hormone 178-199 immunoreactivity is altered in the hypothalamus of the Wistar-Kyoto strain of rat

The rat prepro-thyrotropin releasing hormone (TRH) 178-199 is derived from prepro-TRH by the actions of the endopeptidases, prohormone convertase 1 (PC1) and PC2. PPTRH 178-199 attenuates the synthesis and secretion of adrenocorticotropic hormone (ACTH) from the anterior pituitary both in vitro and in vivo, suggesting an inhibitory action on hypothalamic-pituitary-adrenal (HPA) axis function. This peptide also acts centrally to increase activity and decrease anxiety related behaviors. To elucidate the involvement of this peptide in these functions, we have compared the expression of PPTRH 178-199, PPTRH mRNA, and PC1 and PC2 mRNAs in the Wistar-Kyoto (WKY) and Wistar strains of rat. WKY rats have been shown to possess neuroendocrine abnormalities (HPA hyper-activity) and hyper-emotional behavioral characteristics. Immunohistochemical analysis of PPTRH 178-199 demonstrated significant strain differences in the paraventricular nucleus (PVN) of the hypothalamus and the parastrial nucleus (PSN). WKY rats had significantly greater numbers of immunoreactive (IR) cell body profiles (P<0.0005) than Wistar rats in the PVN and a significantly lower fiber density (P<0.002) in the PSN. Levels of PPTRH, PC1, and PC2 mRNA were not different between strains in any brain region examined. These data suggest that altered levels of PPTRH 178-199 in WKY rats could cause, at least in part, the hyper-activity of the HPA axis and the hyper-emotional behavioral characteristics seen in this rat strain. Such data fit with the hypothesis that PPTRH 178-199 is involved in the regulation of the HPA axis and behavior.

Maternal glucocorticoid hormone influences nerve growth factor expression in the developing rat brain

Rat pups nursed from birth by mothers with increased plasma corticosterone show long-lasting biochemical and behavioral modifications. Here we have investigated nerve growth factor (NGF) concentrations in the basal forebrain, prefrontal cortex and hippocampus of both male and female offspring at 11 days of age. Maternal hypercorticosteronemia was achieved by giving corticosterone-enriched water (200 microg/ml) from delivery. There was a significant increase of NGF in the basal forebrain of both sexes and no changes in the prefrontal cortex. In the hippocampus, an increase in NGF was found in males. These results indicate that a moderate increase of corticosterone in the lactating mother modulates NGF in the developing rat. We propose that these effects contribute directly to the long-lasting behavioral and biochemical modifications in pups nursed by hypercorticosteronemic mothers.

The spiny rat Proechimys guyannensis as model of resistance to epilepsy: chemical characterization of hippocampal cell populations and pilocarpine-induced changes

At variance with pilocarpine-induced epilepsy in the laboratory rat, pilocarpine administration to the tropical rodent Proechimys guyannensis (casiragua) elicited an acute seizure that did not develop in long-lasting status epilepticus and was not followed by spontaneous seizures up to 30 days, when the hippocampus was investigated in treated and control animals. Nissl staining revealed in Proechimys a highly developed hippocampus, with thick hippocampal commissures and continuity of the rostral dentate gyri at the midline. Immunohistochemistry was used to study calbindin, parvalbumin, calretinin, GABA, glutamic acid decarboxylase, and nitric oxide synthase expression. The latter was also investigated with NADPH-diaphorase histochemistry. Cell counts and densitometric evaluation with image analysis were performed. Differences, such as low calbindin immunoreactivity confined to some pyramidal cells, were found in the normal Proechimys hippocampus compared to the laboratory rat. In pilocarpine-treated casiraguas, stereological cell counts in Nissl-stained sections did not reveal significant neuronal loss in hippocampal subfields, where the examined markers exhibited instead striking changes. Calbindin was induced in pyramidal and granule cells and interneuron subsets. The number of parvalbumin- or nitric oxide synthase-containing interneurons and their staining intensity were significantly increased. Glutamic acid decarboxylase(67)-immunoreactive interneurons increased markedly in the hilus and decreased in the CA1 pyramidal layer. The number and staining intensity of calretinin-immunoreactive pyramidal cells and interneurons were significantly reduced. These findings provide the first description of the Proechimys hippocampus and reveal marked long-term variations in protein expression after an epileptic insult, which could reflect adaptive changes in functional hippocampal circuits implicated in resistance to limbic epilepsy.

Expression and function of glycine receptors in striatal cholinergic interneurons from rat and mouse

Although glycine receptors are widely expressed in the forebrain their function is obscure. We studied their activation by two possible endogenous ligands, glycine and taurine, and demonstrate a different expression pattern of glycine receptors in neostriatal cholinergic interneurons from two rodent species. Single-cell-reverse transcription-polymerase chain reaction analysis of glycine receptor-subunit expression was combined with whole-cell recordings from acutely isolated cholinergic interneurons. All cells expressed the alpha2-glycine receptor subunit, the majority (72%) in mice but none in young and aged rats expressed the alpha3-subunit. The beta-subunit expression was associated with both a higher efficacy and a higher potency of the partial agonist taurine. Cells expressing the alpha3-subunit displayed a slower desensitization of taurine responses than of glycine responses, in contrast to cells expressing the alpha2-, beta-subunits where desensitization time constants were similar. Glycine responses were reduced by preapplication of taurine; this effect was more pronounced in cells lacking the alpha3-subunit. We demonstrate interspecies differences and heterogeneity in expression and function of glycine receptors within the same neuronal population in the neostriatum.

"When a rat smells a cat": the distribution of Fos immunoreactivity in rat brain following exposure to a predatory odor

Wistar rats were exposed to a fabric collar that had been worn by a domestic cat. Exposure took place in an open rectangular arena containing a small wooden "hide box". Rats exposed to cat odor spent more than 87% of their time in the hide box during a single 20-min exposure session, whereas rats exposed to a control odor (an unworn collar) spent less than 20% of their time hiding. One hour following this session, rats were killed and Fos immunoreactivity was compared between cat odor-exposed rats, control odor-exposed rats and an additional group that had remained in their home cages. Cat odor-exposed rats showed greater Fos expression than controls in many brain regions, particularly in the medial amygdala, medial hypothalamus and periaqueductal gray. Significant findings included strong and selective induction of Fos in the posteroventral medial amygdaloid nucleus, the premamillary nucleus (dorsal part), ventromedial hypothalamic nucleus (dorsomedial part), dorsomedial hypothalamic nucleus, periaqueductal gray (dorsomedial, dorsolateral and ventrolateral parts) and the cuneiform nucleus. Robust Fos expression in the ventromedial hypothalamus, premamillary nucleus and periaqueductal gray confirms previous suggestions of a role for these areas in predator-induced defensive behavior. Fos immunoreactivity in the medial, but not central or basolateral amygdala is a novel finding and draws attention to this subregion as a possible interface between olfactory input and emotional output.

Distribution of substance P and neurokinin-1 receptor immunoreactivity in the suprachiasmatic nuclei and intergeniculate leaflet of hamster, mouse, and rat

The circadian pacemaker in the hypothalamic suprachiasmatic nuclei (SCN) receives photic information directly via the retinohypothalamic tract (RHT) and indirectly from retinally innervated cells in the thalamic intergeniculate leaflet (IGL) that project to the SCN. Using standard immunohistochemical methods, we examined the presence and distribution of substance P (SP) and the neurokinin-1 receptor (NK-1) in the SCN and IGL of rat and determined whether the patterns of immunostaining generalized to the SCN and IGL of Syrian hamster, Siberian hamster, and mouse. Terminals immunoreactive for SP were sparse within the SCN of Siberian and Syrian hamsters and mouse but were intense in the ventral, retinally innervated portion of the rat SCN. Immunostaining for the NK-1 receptor was mainly absent from the SCN of hamster and mouse. In contrast, a plexus of NK-1-ir cells and processes that was in close proximity to SP-ir terminals was found in the ventral SCN of the rat. Substance P-ir terminals were observed in the IGL of all four species, as were NK-1-ir cells and fibres. Double-labelled IGL sections of hamster or rat revealed SP-ir terminals in close apposition to NK-1-immunostained cells and/or fibres. These data indicate that SP could be a neurotransmitter of the RHT in rat, but not in hamster or in mouse, and they highlight potential species differences in the role of SP within the SCN circadian pacemaker. Such species differences do not appear to exist at the level of the IGL, where SP-ir and NK-1-ir were similar in all species studied.

Connections of the nucleus incertus

The nucleus incertus (NI) is a distinct cell group in caudoventral regions of the pontine periventricular gray, adjacent to the ventromedial border of the caudal dorsal tegmental nucleus. Recent interest in the NI stems from evidence that it represents one of the periventricular sites with the highest expression levels of mRNA encoding the type 1 corticotropin-releasing hormone (CRH) receptor, which has a high affinity for naturally occurring CRH, perhaps accounting for some of the extrapituitary actions of the peptide on autonomic and behavioral components of the stress response. However, almost nothing is known about NI function and hodological relationships. In this paper, we present the results of a systematic analysis of NI inputs and outputs using cholera toxin B subunit as a retrograde tracer and Phaseolus vulgaris-leucoagglutinin as an anterograde tracer. Our retrograde tracer experiments indicate that the NI is in a strategic position to integrate information related to behavioral planning (from the prefrontal cortex), lateral habenular processing, hippocampal function, and oculomotor control. Based on its efferent connections, the NI is in a position to exert significant modulating influences on prefrontal and hippocampal cortical activity, and the nucleus is also in a position to influence brain sites known to control locomotor behavior, attentive states, and learning processes. Overall, the present results support the idea that the NI is a distinct region of the pontine periventricular gray, and together with the superior central (median raphé) and interpeduncular nuclei the NI appears to form a midline behavior control network of the brainstem.