Corticosterone-dependent alterations in utilization of catecholamines in discrete areas of rat brain

This study investigated the impact of chronic adrenalectomy (ADX), and subsequent corticosterone (CORT) replacement to ADX rats, on brain levels of norepinephrine (NE) and dopamine (DA) and their extent of depletion after -methyl-p-tyrosine (-MpT) administration. Seven discrete hypothalamic areas, namely, the paraventricular nucleus (PVN), medial preoptic nucleus (POM), dorsomedial nucleus (DMN), ventromedial hypothalamus (VMH), perifornical lateral hypothalamus (PLH), supraoptic nucleus (SON), and arcuate nucleus/median eminence (ARC-ME), were examined. The steady-state content of NE and DA in all areas remained essentially unaltered 7 days after ablation of the adrenal glands, as well as after subsequent CORT replacement therapy in ADX rats. However, ADX, which reduced circulating CORT levels to 0.3 μg% as compared to > 3.0 μg% in sham rats, caused a significant increase in the depletion of NE following -MpT treatment, in 4 out of the 7 brain sites examined (PVN, PLH, DMN and ARC-ME). In these brain sites, the NE turnover rate (K,pg/μg protein/h) and rate constant (K,h⁻¹) increased following ADX. The chronic subcutaneous CORT implant (200 mg), which raised circulating CORT levels of ADX rats to 11 μg%, prevented this enhancement of NE turnover in the PVN, PLH and ARC-ME, but not the DMN. Unlike NE, DA utilization in the 7 discrete hypothalamic areas of -MpT-treated rats remained unaltered after ablation of the adrenal glands, as well as after the CORT replacement therapy in ADX rats. These results indicate that circulating CORT may have a modulatory role in the regulation of NE in specific discrete hypothalamic areas, and thereby have an impact on the control of various physiological responses.     

Age-related degeneration of the serotoninergic fibers in the zitter rat brain

The serotonin neuron system was studied using immunohistochemical and neurochemical techniques in zitter mutant rats aged 1–14 months, which are characterized by abnormal metabolism of superoxides. The morphology of the serotoninergic neuron system and the serotonin level in the zitter rat were compared to those of age-matched Sprague-Dawley (SD) rats. Up to age 4 month, the density and distribution of serotoninergic fibers in the zitter rat brain were similar to those of control rats. However, several serotoninergic fibers with abnormal morphology, characterized by swollen varicosities, were observed in the cerebral cortex and caudate putamen of 6-month-old zitter rats. The density and distribution of these fibers in other regions of the brain were similar to those of control rats. The abnormal serotoninergic fibers increased in number and extended into other regions of the brain such as the thalamus, hippocampus, and vestibular nucleus. On the other hand, the density of normal serotoninergic fibers decreased throughout the brain of the 14-month-old zitter rat. Abnormal serotoninergic fibers have also been reported in the brain of normal older (24 months) SD rats. Neurochemical analysis revealed lower levels of serotonin, and 5-hydroxyindoleacetic acid, in all cortical areas (prefrontal, parietal, and occipital cortices), the caudate putamen, and the hippocampus of 12-month-old zitter rats. Levels differed significantly in the parietal cortex and hippocampus between the zitter and SD rats. Based on the morphological and neurochemical similarities, the present results suggest that age-related degeneration of serotoninergic fibers occurs in the zitter rat brain. Furthermore, degeneration of serotoninergic fibers appears to be induced by superoxide species. Thus, the zitter rat may provide a good model for studying the neurotoxic effects of superoxide species on the serotoninergic neuron system. Synapse 30:62–70, 1998. © 1998 Wiley-Liss, Inc.     

Distribution of immunoreactive dynorphin B in discrete areas of the rat brain and spinal cord

The distribution of immunoreactive (ir)-dynorphin B in 101 microdissected rat brain and spinal cord regions was determined using a specific radioimmunoassay. The highest concentration of dynorphin B in brain was found in the substantia nigra (1106.2 fmol/mg protein). Very high concentrations of ir-dynorphin B (> 400 fmol/mg protein) were also found in the lateral preoptic area, parabrachial nuclei and globus pallidus. Relatively high concentrations of ir-dynorphin B (250–400 fmol/mg protein) were found in 19 nuclei, including the periaqueductal gray matter, anterior hypothalamic nucleus, median eminence, nucleus accumbens and hippocampus. Moderate levels of the peptide (between 100 and 250 fmol/mg protein) were found in 42 brain nuclei such as the perifornical nucleus, nucleus of the diagonal band, medial forebrain bundle, and dorsal premamillary nucleus. Low concentrations of ir-dynorphin B (< 100 fmol/mg protein) were found in 28 brain areas, e.g. cerebral cortical structures (parietal, cingulate, frontal), claustrum, olfactory bulb, lateral and periventricular thalamic nuclei. The cerebellar cortex has the lowest dynorphin B concentration (53.7 fmol/mg protein). Spinal cord segments exhibit low or moderate (cervical segment) levels of the peptide. The neurointermediate lobe of the pituitary gland is extremely rich in ir-dynorphin B (11,047.1 fmol/mg protein).     

Cholecystokinin and substance P concentrations in discrete areas of the rat brain: sex differences

Cholecystokinin (CCK) and substance P (SP) concentrations were measured in discrete brain areas of adult male and diestrous female rats. Significant sex differences in CCK concentration were found in the ventromedial hypothalamic area, medial and lateral preoptic area, nucleus of the diagonal band of Broca, ventral tegmental area, entorhinal and in several cortical areas. No sex differences in SP concentrations were observed in any of these areas. However, significant sex differences in SP concentration were found in the amygdala. These data indicate that the CCK and to some extent the SP systems are sexually differentiated in certain brain areas.     

Age-related changes of vasopressin content of microdissected areas of the rat brain

Vasopressin contents of posterior pituitaries and intra- and extrahypothalamic nuclei of brains from 3-month and 24-month-old Long-Evans rats and from Brattleboro rats heterozygous (HEDI) and homozygous (HODI) for diabetes insipidus were measured by radioimmunoassay.The pituitary content of vasopressin was highest in young rats and was significantly lower in HEDI tissue. The peptide was not detected in HODI pituitaries.In the brain regions studied both aged and HEDI rats showed reduced vasopressin contents as compared to young animals. In light of evidence of memory deficiencies in both HEDI and HODI rats, the possibility arises that memory decrements associated with senescence may be related to altered vasopressin synthesis and/or secretion occurring with aging of these neuronal systems.     

Darkness induced neuroplastic changes in the serotoninergic system of the chick retina

Sensory experience is critical for the formation of neuronal circuits and it is well known that neuronal activity plays a crucial role in the formation and maintenance of synapses. In the vertebrate retina, exposure to different environmental conditions results in structural, physiological, neurochemical and pharmacological changes. Serotoninergic (5HT) amacrine cells of the chicken retina are bistratified interneurons whose primary dendrites descend through the inner nuclear layer (INL) to branch in the inner plexiform layer (IPL) forming two plexi, an outer network, localized to sublamina 1, and an inner network, localized to sublamina 4 and 5 of the IPL. Their development is temporally correlated with the establishment of synapses in the retina and with the emergence of the typical adult electroretinogram. It is unknown, however, which role these cells play in processing visual information and whether visual deprivation modifies their phenotype. Here, we show that, in the chicken, red-light rearing from hatching to postnatal day 12 significantly alters the stratification pattern of 5HT amacrine cells, inhibiting their age-dependent pruning measured with morphometric and densitometric procedures; as well as increasing serotonin immunoreactivity measured as relative optical density. This change in dendritic arborization, accompanied by an increase in serotonin concentration in dark adapted conditions, may decrease visual threshold, thus increasing visual sensitivity.     

Age-related changes of the nitric oxide system in the rat brain

This work examines the age-related changes of the NO pathway in the central nervous system (CNS), analyzing nitric oxide synthase (NOS) isoform expression, the level of nitrotyrosine-modified proteins, and the NOS activity in the cerebral cortex, decorticated brain (basal ganglia, thalamus, hypothalamus, tegtum and tegmentum) and cerebellum of young, adult and aged rats. Our data demonstrate that the different NOS isoforms are not uniformly expressed across the CNS. In this sense, the nNOS and eNOS isoenzymes are expressed mainly in the cerebellum and decorticated brain, respectively, while the iNOS isoenzyme shows the highest level in cerebellum. Concerning age, in the cerebral cortex nNOS significantly increased its expression only in adult animals; meanwhile, in the cerebellum the eNOS expression decreased whereas iNOS increased in adult and aged rats. No age-related changes in any isoform were found in decorticated brain. NOS activity, determined by nitrate plus nitrite quantification, registered the highest levels in the cerebellum, where the significant increase detected with aging was probably related to iNOS activity. The number of nitrotyrosine-modified immunoreactive bands differed among regions; thus, the highest number was detected in the decorticated brain while the cerebellum showed the least number of bands. Finally, bulk protein nitration increased in cerebral cortex only in adult animal. No changes were found in the decorticated brain, and the decrease detected in the cerebellum of aged animals was not significant. According to these results, the NO pathway is differently modified with age in the three CNS regions analyzed.     

Tyrosine hydroxylase and dopamine-beta-hydroxylase: distribution in discrete areas of the rat limbic system.

Tyrosine hydroxylase and dopamine-beta-hydroxylase have been measured in 34 discrete areas and nuclei of the limbic system of the rat. Both enzymes showed an uneven distribution in this system. The ratio between tyrosine hydroxylase and dopamine-beta-hydroxylase activities showed a significant correlation when compared with the ratio of dopamine and norepinephrine concentrations for the areas studied. The results strongly suggest that dopaminergic terminals are present in discrete areas of the limbic cortex, and several septal and amygdaloid nuclei, and allow the precise localization of dopaminergic and noradrenergic areas in the limbic system.     

Cellular changes in rat brain areas associated with neonatal hippocampal damage.

The neonatal destruction of the ventral hippocampus was introduced as a model to recreate features of schizophrenia in the rat. While behavioral consequences of this intervention have been studied in detail, less is known about the cellular processes underlying the deviant behavior. We studied in rats (neonatally or adult lesioned, controls) brain areas receiving or not receiving hippocampal projections. The number of neurons and the expression of the cell markers L-ornithine decarboxylase, nitric oxide synthase/NADPH diaphorase, calretinin and GFAP were estimated. Reduced numbers of neurons and increased immunostaining for ornithine decarboxylase and nitric oxide synthase in the prefrontal, perirhinal and entorhinal cortex of neonatally but not adult lesioned rats or controls demonstrate persistent cellular changes after ventral hippocampus damage.     

Rapid changes in GABA binding induced by stress in different areas of the rat brain

Rats habituated to handling preceding sacrifice have higher [3H]GABA receptor binding in different brain areas (cerebellum, frontal cortex, caudate nucleus) than naive animals. The increase in GABA binding in handling-habituated rats is due to an increase in the number of receptors (Bmax) with no changes in the affinity of GABA binding for its ligand (Kd). Foot shock causes a sudden fall in GABA binding in handling-habituated rats but does not, or only slightly, in naive ones. The results indicate that stress causes a rapid decrease in GABA receptor binding in the central system and that the GABA binding values which are usually considered as normal are, in fact, values decreased by the handling manoeuvers preceding sacrifice.     

Involvement of the central nervous system in cysticercosis]

The involvement of the central nervous system in cysticercosis was demonstrate as an incidental finding in a frequence of 0,3% in 4000 autopsied cases. Most of the 12 patients came from rural areas of the State of Bahia. The low frequence compared to other sites reported in Brasil shows that the neurcysticercosis does not represent an important problem in Bahia. The host tissue response observed was represented by a chronic fibrosing inflammatory type of reaction. This study points out the importance of the methenamine silver stain (Grocott) in the identification of the degenerated embryo inside the fibrous and/or calcified lesions.     

Glycerol oxidation in discrete areas of rat brain from young, adolescent, and adult rats

We have reported previously that the oxidation rate of [1,3-14C] glycerol to 14CO2 is lower in whole brain homogenates from neonatal rats and increases about 30% during the suckling period to adult levels. To determine whether there are developmental changes in glycerol oxidation in discrete regions of brain, we examined the oxidation of glycerol by homogenates of hypothalamus, cerebellum, brain stem, hippocampus, and cerebral cortex of young (4-6 days) and older (18-20 days) pups and adult (greater than 90 day) rats. The oxidation was measured at both low (0.2 mM) and high (2.0 mM) concentrations of glycerol, since the oxidation of glycerol by brain tissue has been shown to exhibit biphasic kinetics. At each age, and with both concentrations of glycerol, there were significant differences among the discrete brain regions. Although the rate of glycerol oxidation increased with age in most areas of brain, each brain region had a distinct developmental profile. In the hypothalamus, the oxidation of glycerol increased significantly between 4-6 days and adult levels at 18-20 days. The oxidation of glycerol was essentially the same in homogenates of cortex from young and older pups, but it was significantly increased in adults. In contrast with other brain regions, the oxidation of glycerol by brain stem was highest at 4-6 days and significantly decreased with age. The developmental profile of glycerol oxidation in hippocampus and cerebellum was particularly complex, since it increased with age at low, but not at high, concentrations of glycerol. This developmental pattern in hippocampus and cerebellum could be related to changes in the biphasic kinetics of glycerol oxidation and suggests that glycerol metabolism is different in these two areas of brain compared with other areas of brain.     

Effects on locomotor activity after local application of (+)-UH232 in discrete areas of the rat brain

Summary The preferential dopamine autoreceptor, and slightly D3 preferring, antagonist (+)-UH232 (cis-(+)-(1S,2R)-5-methoxy-1-methyl-2-(n-dipropylamino) tetralin) increases locomotor activity and synaptic dopamine release in the nucleus accumbens and striatum after systemic administration to the rat. As shown in this study, (+)-UH232, was unable to produce anincrease in locomotor activity measured for 60 minutes after local administration into the terminal or somato-dendritic regions of the mesolimbic dopamine pathways or into the lateral ventricle. Instead, a dose dependent decrease of spontaneous locomotor activity after local application (0.05–50.0 nmol/ side) of (+)-UH232 into the nucleus accumbens, was seen. A similar reduction in locomotor activity was produced by the classical dopamine antagonist raclopride. Analysis of the dose*time interactions on locomotor activity did, however, indicate that there is a significant dose*time interaction after local application of (+)-UH232 into the lateral ventricle and VTA. Raclopride, on the other hand, produced only a weak time dependent effect in the VTA. The potential problem of Leao's spreading depression in micro-injection experiments were considered, however, spreading depression does not seem to influence the effects of (+)-UH232 locally applied into the nucleus accumbens. In conclusion, both (+)-UH232 and raclopride produced a dose dependent decrease in spontaneous locomotor activity when examined as the total activity count over 60 minutes after local application into the N Acc.     

Expression of coat proteins changes during postnatal development in selected areas of the rat brain

It is well known that clathrin-mediated endocytosis is crucial for the normal functioning and integrity of neurons in the central nervous system. In this study we attempted to correlate the expression of coat proteins with development in different areas of rat brain. By Western blot, we studied the expression of AP-2, GGA1 and GGA2 in striatum, cerebellum, brain stem, cerebral cortex and hippocampus of newborn rats and during post-natal development; 5, 15, 30, 60, 90 or 150 days after birth. We observed that the expression of the α2 subunit of AP-2 increased substantially between the 15th and 30th day after birth in all areas studied, excepting the cerebellum and cortex. On the other hand, the expression of the α1 subunit does not change significantly during the development in any of the areas under study. We also noted that the expression of the μ2 subunit did not follow the pattern of α2 during development. In general terms, the expression of GGA1 and GGA2 followed a similar pattern to that of AP-2, although these proteins increased significantly in the cerebral cortex from the 15th day after birth. Moreover, presenilin-1, a protein associated with aging and neurodegeneration, shows an expression pattern similar to coat proteins in the striatum and cortex. These results suggest that proteins that conform the intracellular transport machinery in the brain cells seems to accompany development, according to the maturation of the different brain areas.     

Age-dependent changes in the β-endorphin content of discrete rat brain nuclei

Concentrations of β-endorphin were measured by radioimmunoassay in discrete brain nuclei of young (3 months) and old (24 months) rats. The β-endorphin content of all major structures known to contain this peptide with the exception of the eminence, is reduced (50.3 ± 2.8% of control) in old rats.     

Postmortem changes in the level of brain proteins

A systematic study on postmortem changes of brain proteins has not been performed so far and information is limited to basic principles of specific or nonspecific proteolysis or proteolysis of individual proteins. We studied protein level alterations in rat brain of animals kept at 23 degrees C for several postmortem times up to 72 h. Brain tissue protein extracts were analyzed by two-dimensional electrophoresis and the proteins with different levels were identified by matrix-assisted laser desorption ionization mass spectrometry. The changes observed mainly concerned structural proteins and enzymes. The levels of dihydropyrimidinase-related protein-2 decreased within 6 h and two new spots were detected representing shorter forms of the protein. Most of the other alterations appeared about 48 h postmortem. The most significant were reduced levels of neurofilament, alpha-internexin, synaptosomal-associated protein 25, glial fibrillary acidic protein, heat shock proteins, and dynamin-1; increased levels of 14-3-3 proteins and spectrin; and generation of shorter forms of certain proteins, such as tubulins, actin, and serum albumin. The results may be useful in neuropathology and brain protein studies.     

Immunohistochemical characterization of serotoninergic afferent pathways in the visual system of the rat

Using the immunohistochemical PAP-method occurrence, distribution and terminal aborization of serotoninergic axons were investigated in the visual system of the albino rat. The present study reveals that the innervation varies in quantitative and qualitative manner in the different parts of the visual system. A sparsly serotoninergic innervation was observed in the dorsal lateral geniculate body (d lgb) and in the nucleus lateralis posterior. An intensive serotoninergic innervation was found in the lateral part of the ventral lateral geniculate body (v lgb) and in the area praetectalis. Serotoninergic axons show a lamina specific orientation in the colliculus superior and in the visual cortex. Our findings indicate that serotoninergic axons have an intensive terminal aborization in subcortical visual nuclei, which are more or less connected with oculomotoric functions.