Olfactory Tuberculum Research Articles

Comparative evaluation of the effects of short-term inhalation exposure to diesel engine exhaust on rat lung and brain

Combustion-derived nanoparticles, such as diesel engine exhaust particles, have been implicated in the adverse health effects of particulate air pollution. Recent studies suggest that inhaled nanoparticles may also reach and/or affect the brain. The aim of our study was to comparatively evaluate the effects of short-term diesel engine exhaust (DEE) inhalation exposure on rat brain and lung. After 4 or 18 h recovery from a 2 h nose-only exposure to DEE (1.9 mg/m3), the mRNA expressions of heme oxygenase-1 (HO-1), inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), and cytochrome P450 1A1 (CYP1A1) were investigated in lung as well as in pituitary gland, hypothalamus, olfactory bulb, olfactory tubercles, cerebral cortex, and cerebellum. HO-1 protein expression in brain was investigated by immunohistochemistry and ELISA. In the lung, 4 h post-exposure, CYP1A1 and iNOS mRNA levels were increased, while 18 h post-exposure HO-1 was increased. In the pituitary at 4 h post-exposure, both CYP1A1 and HO-1 were increased; HO-1 was also elevated in the olfactory tuberculum at this time point. At 18 h post-exposure, increased expression of HO-1 and COX-2 was observed in cerebral cortex and cerebellum, respectively. Induction of HO-1 protein was not observed after DEE exposure. Bronchoalveolar lavage analysis of inflammatory cell influx, TNF-α, and IL-6 indicated that the mRNA expression changes occurred in the absence of lung inflammation. Our study shows that a single, short-term inhalation exposure to DEE triggers region-specific gene expression changes in rat brain to an extent comparable to those observed in the lung.

Differential effects of a selective dopamine D1-like receptor agonist on motor activity and c-fos expression in the frontal-striatal circuitry of SHR and Wistar-Kyoto rats

BackgroundMolecular genetic studies suggest the dopamine D1 receptor (D1R) may be implicated in attention-deficit/hyperactivity disorder (ADHD). As little is known about the potential motor role of D1R in ADHD, animal models may provide important insights into this issue.MethodsWe investigated the effects of a full and selective D1R agonist, SKF-81297 (0.3, 3 and 10 mg/kg), on motor behaviour and expression of the plasticity-associated gene, c-fos, in habituated young adult male Spontaneously Hypertensive Rats (SHR), the most commonly used animal model of ADHD, and Wistar-Kyoto (WKY; the strain from which SHR were derived).ResultsSHR rats were more behaviourally active than WKY rats after injection with vehicle. The 0.3 mg/kg dose of SKF-81297 increased motor behaviour (locomotion, sifting, rearing, and sniffing) in both SHR and WKY rats. Total grooming was also stimulated, but only in WKY rats. The same dose increased c-fos mRNA expression in the piriform cortex of both strains. The 3 mg/kg dose increased sifting and sniffing in both strains. Locomotion was also stimulated towards the end of the testing period. The intermediate dose decreased total rearing in both strains, and produced a significant increase in c-fos mRNA in the striatum, nucleus accumbens, olfactory tuberculum, and in the cingulate, agranular insular and piriform cortices. The 10 mg/kg dose of SKF-81297 produced a biphasic effect on locomotion, which was characterized by an initial decrease followed by later stimulation. The latter stimulatory effect was more pronounced in SHR than in WKY rats when compared to their respective vehicle-injected groups. The 10 mg/kg dose also stimulated sifting and sniffing in both strains. Both the 3 and 10 mg/kg doses had no effect on total grooming. The 10 mg/kg dose induced significantly higher levels of c-fos mRNA expression in the nucleus accumbens and adjacent cortical regions (but not striatum) of SHR when compared to WKY rats.ConclusionThe present results suggest a potential alteration in D1R neurotransmission within the frontal-striatal circuitry of SHR involved in motor control. These findings extend our understanding of the molecular alterations in SHR, a heuristically useful model of ADHD.

Genetic differences in brain monoamines level in Pietrain and Duroc pigs exposed to acute restraint stress

SummaryThe distribution and endogenous concentrations of norepinephrine (NE), epinephrine (E), dopamine (DA) as well as DA metabolites 3,4‐dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA), 5‐hydroxytryptamine (5‐HT) and the main 5‐HT metabolite – 5‐hydroxyindole‐3‐acetic acid (5‐HIAA), were measured by HPLC in 15 brain areas of control and immobilized adult Duroc (D) and Pietrain (P) pigs. The animals were immobilized for 15, 30 and 60 min in the prone position. Control pigs displayed the pattern of regional distribution of brain monoamines similar to that described in other species. Absolute values of NE and E were much higher in the hypothalamus and the preoptic area of pigs than in other species. The concentration of E was seven times higher in the hippocampus posterior in P pigs as compared to D pigs. Also, in most structures DOPAC/DA ratio was relatively high, which points to strains related difference in the turnover of dopamine. In control animals, statistical differences in the bioamine contents were seen between both strains in 25 cases. Epinephrine accounted for more than 12% of the total concentration of both amines in D and 15% in P, this proportion was the highest among the structures compared. The highest concentration of DA and its metabolites – DOPAC and HVA, was revealed in the caudate nucleus and in the nucleus accumbens. Of other structures, the substantia nigra (SN), the septum and the ventral tegmental area (VTA) contained relatively high concentrations of DA, DOPAC and HVA. The 5‐HT level varied from the lowest concentration in the hippocampus posterior, cornu ammonis, nucleus accumbens and the caudate nucleus to the highest concentration in the hypothalamus, the SN, and brain stem areas. This distribution was paralleled by corresponding concentration of 5‐HIAA, being the highest in raphe nuclei (RN). The most conspicuous changes produced by immobilization stress consisted of a substantial decrease in the hypothalamic levels of NE and E in both strains of pig. The level of NE was always higher in D than in P in cornu ammonis, hippocampus posterior, nucleus caudatus, SN, septum, hypothalamus medialis, tectum and olfactory tuberculum. The same was for E in: SN, septum, hypothalamus medialis, and olfactory tubercle. DA, DOPAC and HVA, were changed primarily in SN in P pigs, and in RN in P and D animals. Serotonin (5‐HT) level increased substantially in RN in P pigs. 5‐HIAA level was highly elevated in the RN being always higher in P than in D pigs and in PAG. We suggest that restraint immobilization stress lead to compensatory changes in both brain monoaminergic systems. These changes may affect coping with stress demands mostly in the structures that are proposed to play a major role in the pig responsiveness to acute stress conditions.

The effect of acute restraint stress on regional brain neurotransmitter levels in stress-susceptible pietrain pigs.

Concentrations of noradrenaline (NA), adrenaline (A), dopamine (DA), 5-hydroxytryptamine (5-HT), the DA metabolites 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) and the main 5-HT metabolite 5-hydroxyindole-3-acetic acid (5-HIAA) were measured using HPLC in 16 brain areas of control and immobilized Pietrain pigs. The animals were immobilized for 15, 30 and 60 min in the prone position. Control pigs showed patterns of regional distribution of brain monoamines similar to those described for rats, dogs and Duroc pigs. However, the absolute values of NA and A in the hypothalamus and preoptic area were much higher than those in rats and dogs, but similar to those in Duroc pigs. The concentrations of dopamine and its metabolites DOPAC and HVA were highest in the caudate nucleus, the nucleus accumbens, the olfactory tubercle and the ventral tegmental area. The distributions of serotonin and its metabolite 5-HIAA were similar in all examined structures. DOPAC/DA and HVA/DA ratios were higher in the cornu ammonis, the hippocampus posterior and the raphe nuclei than in other structures, which suggests brain structure-related differences in dopamine turnover. The greatest decreases in NA and A content were observed in the hypothalamus, the preoptic area and the olfactory tuberculum during the first 30 min of immobilization stress. 5-HT turnover was increased in the raphe nuclei, while DA turnover was affected in the raphe nuclei, the septum, the substantia nigra and the olfactory tubercle. We suggest that acute immobilization stress caused differences in regional patterns of brain biogenic amines, thereby maintaining adequate transmitter levels during stress in stress-susceptible pigs.

Expression of Soluble Guanylyl Cyclase Gene in Adult Rat Brain

The synthesis of the intracellular messenger, cyclic GMP, is catalysed by particular or soluble guanylyl cyclase (sGCY). sGCY is activated by nitric oxide, a compound with putative neurotransmitter functions, especially in long-term potentiation. Hybridization histochemistry with a probe complementary to the rat lung large (alpha 1) subunit was used to assess the exact localization of sGCY mRNA in the rat brain. Many cells in the olfactory bulb contained sGCY mRNA. In the whole cerebral cortex, sGCY mRNA was found in all layers, with a predominance in layers II-III. A similar pattern was found in the olfactory tuberculum, in continuation with the piriform cortex and the cortical amygdaloid nucleus. All parts of the striatum expressed sGCY mRNA. sGCY mRNA was also found in the habenula medialis, in the pinealis in some diencephalic nuclei, and in the granule cell layers of the cerebellum. This study provides a description of the normal anatomy of sGCY gene expression in the rat forebrain as a basis for the study of the modulation of expression after physiological and pharmacological manipulations.

Cellular distribution of immunoreactive somatostatin in the basal forebrain of horses and ponies

Summary In other experimental models, somatostatin (SRIF) helps coordinate central nervous system (CNS) activity associated with the response to stress. It also plays an important role in the effects of exercise, stress and bacterial infections on growth hormone (GH) release and it may interact with specific SRIF receptors found on lymphocytes. Pituitary GH is a potent immunomodulatory hor- mone which is important to normal function of the thymus and a wide range of immune defense mechanisms. This experiment mapped the distribution of immunoreactive (ir) SRIF in the basal forebrain of horses and ponies. Results are compared to those for other species in order to determine if the anatomical substrate for stress-dependant SRIF effects may be similar to that described for other animal models. Immersion fixed brain tissues were obtained from animals submitted for euthanasia and/or necropsy. Alternate sections were stained for ir-SRIF using characterized polyclonal SRIF antibody and the peroxidase-anti-peroxidase technique, as previously described. Distribution of SRIF cells and fibers was mapped on projection drawings following light microscopic examination. Tissues in this analysis included cell groups at the border between the telencephalon and the rostral diencephalon, the hypothalamus, caudate nucleus (n) subthalamus and thalamus. At rostral levels, ir-SRIF was widely dispersed throughout medial tissues. Caudally, pronounced immunoreactivity was found in ventromedial tissues. Reactive perikarya were localized in the caudate n, olfactory tuberculum, n of the lamina terminalis, rostral preoptic n, suprachiasmatic n, periventricular n, supraoptic n, paraventricular n, arcuate n and ventromedial n. Numerous SRIF fibers extended into the lateral septum, all preoptic n, paraventricular n, rostral hypothalamic n, dorsomedial n, ventromedial n and mammillary n. Reactive fibers were also found in midline thalamic n, perifomical areas, the zona incerta and the habenular n. This distribution is similar to that described in most vertebrates. It reflects the role of SRIF in multiple neurocrine interactions as well as its neuroendocrine activity. Results from this experiment suggest that equine SRIF is likely to participate in neural and endocrine pathways similar to that for other mammalian species. Similar localization patterns also suggest that the coordination of SRIF cell functions within the equine CNS may be comparable to that in other species. This suggests that studies in other species are likely to facilitate the characterization of control mechanisms for SRIF secretion in the equine species.

Distribution of protein kinase C-like immunoreactive neurons in rat brain

Distribution of protein kinase C in the CNS of rat is presented based on immunohistochemical analysis with monoclonal antibodies against this protein kinase. Protein kinase C-like immunoreactivity was discretely localized and associated with neurons. Most, if not all, glial cells were not significantly stained. The greatest density of the immunoreactive material was seen in the following regions: the olfactory bulb (external plexiform layer), olfactory tuberculum, anterior olfactory nucleus, cerebral cortex (layers I and IV), pyriform cortex, hippocampus (strata radiatum and oriens), amygdaloid complex (central and basolateral nuclei), cerebellar cortex (molecular layer), dorsal cochlear nucleus, nucleus spinal tract of the trigeminal nerve, and dorsal horn of the spinal cord (substantia gelatinosa). Image analysis revealed that the regional distribution of the protein kinase C-like immunoreaction generally agreed with that of phorbol ester-binding sites. Immunoreactive perikarya were found in the following areas: the cerebral cortex (layers V and VI), caudate putamen, hippocampus, thalamus, amygdaloid complex, medial and lateral geniculate nucleus, superior colliculus, cerebellar cortex, nucleus spinal tract of the trigeminal nerve, dorsal cochlear nucleus, and dorsal horn of the spinal cord. Intense protein kinase C-like immunoreactivity in the neuron was observed both in the membrane and cytoplasm of the perikarya, dendrites, axons, and axon terminals, while weak immunoreaction was seen in the nuclei but almost never in the nucleoles. A map of protein kinase C-containing neurons was constructed. Such an uneven distribution in the brain suggests that this enzyme may play roles in controlling neuronal function in the areas noted.

Nonlinear relationship between impulse flow and dopamine released by rat midbrain dopaminergic neurons as studied by in vivo electrochemistry

Mesolimbic dopaminergic neurons discharge either in a single spike mode or in a bursting pattern. In order to investigate the influence of these patterns on dopamine release, extracellular dopamine was electrochemically monitored in vivo in the olfactory tuberculum of anaesthetized rats by means of two approaches. In the first, a pure signal, unequivocally corresponding to extracellular dopamine, was recorded every minute from pargyline treated rats by differential normal pulse voltammetry combined with electrochemically treated carbon fibre electrodes. In the second, the differential current solely due to oxidation of all the catechols was monitored every l s in drug-free rats by differential pulse amperometry. In basal conditions this current was mainly due to extracellular DOP AC. However, electrical stimulation of the dopaminergic pathway for 20 s elicited an immediate increase in this signal. This effect was due to evoked dopamine release since it was strongly enhanced by amphetamine (2 mg/kg) or pargyline (75 mg/kg) injections. As studied with both approaches, the evoked increase in extracellular dopamine concentration was immediate and lasted as long as the stimulation. The amplitude of the effect depended on the frequency of the stimulation (from 3 to 14 Hz) in an exponential manner but never exceeded 1 μ M dopamine. Bursting stimulations (frequency within the trains: 14 Hz) were twice as potent as regularly spaced ones, having the same average frequency (5 Hz). In conditions which mimicked the spontaneous activity of dopaminergic neurons when they switch from one pattern to the other (4 Hz regularly spaced stimulation versus trains at a mean frequency of 6 Hz), the bursting stimulations were found to be up to 6 times more potent. Therefore, as regards the functional efficacy of DA neurons, bursting might be much more important than mean firing frequency.

Modulating role of lithium on dopamine turnover, prolactin release, and behavioral supersensitivity following haloperidol and reserpine.

The effects of haloperidol, reserpine, and concomitant lithium were evaluated in biochemical, endocrine, and behavioral studies in the rat. Concomitant administration of a chronic regimen of haloperidol and lithium did not prevent the development of tolerance as noted by dopamine metabolites in the striatum or olfactory tuberculum. Nor did chronic lithium alter behavioral response in rats treated with reserpine and challenged with the dopamine agonist apomorphine. Additionally, prolactin release was increased by haloperidol, but was not altered by acute or chronic lithium treatment. These findings are discussed in the light of present knowledge of pre- and postsynaptic receptor changes and the effects of lithium.

Effect of a TRH analog (DN-1417) on tyrosine hydroxylase activity in discrete areas of rat brain.

Tyrosine hydroxylase (TH), the rate-limiting enzyme in catecholamine biosynthesis was assayed in 12 regions of rat brain following chronic treatment with DN -1417 (γ-butyrolactone-γ-carbonyl-histidyl-prolinamide), a synthetic TRH analog. Chronic DN-1417 treatment (20 mg/kg i. p., 7 daily injections) increased the TH activity in the ventral tegmental area, nucleus arcuatus and nucleus locus coeruleus, and decreased the TH activity in the frontal cortices, olfactory tuberculum and nucleus paraventricularis. No significant change in TH activity was observed in the nucleus accumbens, nucleus caudatus putamen, median eminence and substantia nigra. These results suggest that DN -1417 exerts some of its effects through dopaminergic neurons, as well as noradrenergic neurons; and the mesolimbic and mesocortical dopamine system may be intimately involved in the central actions of DN-1417.