Biomedical subjects

M Herrera-Marschitz

Publications and source records attributed to M Herrera-Marschitz.

At least 37 records · Page 2Linked to original sources

PubMed1999

Dopamine D1 receptor modulation of glutamate receptor messenger RNA levels in the neocortex and neostriatum of unilaterally 6-hydroxydopamine-lesioned rats.

The effect of treatment with the D1 dopamine receptor agonist SKF 38393 on the expression of metabotropic glutamate receptor 1, 3, 4 and 5 receptor subtypes and of the glutamate N-methyl-D-aspartate ionotropic receptor subunits NRI, NR2A and NR2B was analysed using in situ hybridization. We studied the neocortex and neostriatum of normal rats and of rats unilaterally treated with 6-hydroxydopamine, a neurotoxin that, after intracerebral injection into the ventral tegmental area, causes selective degeneration of the ascending dopamine pathway. In the 6-hydroxydopamine-lesioned rats, metabotropic glutamate receptor subtype 3 messenger RNA levels were ipsilaterally increased in the neocortex and neostriatum, while the levels of metabotropic glutamate receptor subtype 4 messenger RNA were bilaterally increased in both regions. When administered to the 6-hydroxydopamine-lesioned rats, the D1 receptor agonist SKF 38393 (3 x 20 mg/kg, s.c.) produced a bilateral decrease in the expression of the metabotropic glutamate receptor subtype 1 and 5 receptor messenger RNA levels in the neocortex and neostriatum. In the neostriatum, SKF 38393 attenuated the ipsilateral increase in the expression of striatal metabotropic glutamate receptor subtype 3 messenger RNA produced by the 6-hydroxydopamine lesion. Furthermore, SKF 38393 produced a bilateral decrease in the levels of NRI receptor subunit messenger RNA and, in contrast, an increase in the striatal NR2B messenger RNA levels. All of these effects were abolished by the D1 receptor antagonist SCH 23360. These results indicate a differential D1 receptor-mediated modulation of the expression of some glutamate receptor subtypes in the neostriatum and neocortex, in agreement with the idea of a functional coupling between dopamine and excitatory amino acid systems in both regions. Thus, pharmacological targeting of excitatory amino acid systems could provide alternative or complementary treatment strategies for diseases involving dopaminergic systems in the striatum (e.g., Parkinson's disease) and cortex (e.g., schizophrenia).

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗

PubMed1999

Nitric oxide and nitric oxide synthase in the early phase of perinatal asphyxia of the rat.

The role of nitric oxide, a compound involved in neurotransmission and regulation of cerebral blood flow, in cerebral ischemia is still not fully elucidated yet. Although well studied in adult systems of cerebral ischemia/hypoxia, information on nitric oxide in perinatal asphyxia is limited and, in particular, no direct evidence for its generation has been provided. We therefore decided to study nitric oxide generation in brain of asphyctic rat pups by biophysical and biochemical methods. We used a simple, non-invasive rat model resembling the clinical situation in perinatal asphyxia: rat pups delivered by Caesarean section were placed into a water bath at 37 degrees C still in patent membranes for various asphyctic periods (up to 20 min). Brain pH, cerebral blood flow, neuronal nitrix oxide synthase messenger RNA (by northern and dot blot analysis), immunoreactive protein (by western blot analysis) and nitric oxide synthase activity were determined; generation of nitric oxide was evaluated directly by electron paramagnetic resonance spectroscopy. Neuronal nitric oxide synthase messenger RNA activity and nitric oxide generation were unaffected, whereas neuronal nitric oxide synthase-immunoreactive protein of 150,000 mol. wt was decreased and of 136,000 mol. wt was increased with the length of the asphyctic period. This is the first report on direct evidence for the generation of nitric oxide in perinatal asphyxia and we demonstrate that nitric oxide production remains unaffected even by 20 min of asphyxia, at a time-point when cerebral blood flow was increased four-fold and severe acidosis was present. However, it was found that levels of immunoreactive neuronal nitric oxide synthase of 136,000 mol. wt were increased paralleling the length of asphyxia. Levels of the 150,000 mol. wt immunoreactive neuronal nitric oxide synthase protein decreased, suggesting a different regulation pattern. Thus, the present biochemical and biophysical results form the basis for further investigations on nitric oxide in perinatal asphyxia.

Animals↗

PubMed1999

Neurocircuitries of the basal ganglia studied in organotypic cultures: focus on tyrosine hydroxylase, nitric oxide synthase and neuropeptide immunocytochemistry.

The nigrostriatal and mesolimbic systems of the rat were reconstructed using an organotypic culture model, whereby neonatal brain tissue was grown in vitro for approximately one month. The nigrostriatal system comprised of tissue from the substantia nigra, the dorsal striatum and the frontoparietal cortex, while the mesolimbic system included the ventral tegmental area, ventral striatum (including the fundus striati, accumbens nucleus, olfactory tubercle, lateral septum, ventral pallidum and piriform cortex) and cingulate cortex. These regions were also cultured alone or in pairs. The cultures were monitored in vitro, and after one month fixed in a formalin-picric acid solution, and processed for immunohistochemistry using antibodies raised against tyrosine hydroxylase, nitric oxide synthase, preprocholecystokinin, glutamate decarboxylase, neuropeptide Y, dopamine- and cyclic AMP-regulated phosphoprotein-32 and glial fibrillary acidic protein. The tissue survived in single, double or triple cultures, although differences were found depending upon the source and combination of cultured region. Neurons had localization and shape as in vivo. Local networks were especially prominent in the mesencephalon, where both tyrosine hydroxylase-positive axons spread from the "substantia nigra" to the rest of the tissue, and where nitric oxide synthase-positive networks also surrounded tyrosine hydroxylase-positive neurons. Glutamate decarboxylase-positive nerve terminals formed dense networks around tyrosine hydroxylase-positive neurons. In the striatum, nitric oxide synthase and dopamine- and cyclic AMP-regulated phosphoprotein-32 neurons were surrounded by tyrosine hydroxylase-positive nerve terminals. The nigral and ventral tegmental area dopamine neurons projected to striatal and cortical structures, but the projection from the ventral tegmental area to the cingulate cortex was more prominent. With regard to co-existence, preprochole-cystokinin-like immunoreactivities was found in many tyrosine hydroxylase-positive neurons and neuropeptide Y- and nitric oxide synthase-like immunoreactivity co-existed in striatal and cortical tissues. In general terms, the chemical neuroanatomy in the cultures was similar to that described earlier in vivo. Nitric oxide synthase staining was particularly intense. Taken together, the organotypic model captures many of the morphological and neurochemical features seen in vivo, providing a valuable model for studying neurocircuitries of the brain in detail, where 'normal' and 'pathological' conditions can be simulated.

Animals↗

PubMed1999

Modulation of neurotransmitter release in the basal ganglia of the rat brain by dynorphin peptides.

Microinjection studies have found that although dynorphin peptides decrease dopamine release in the rat basal ganglia, the nonselective opiate antagonist naloxone produces the opposite effect. To investigate the contribution of the dynorphin pathways to a tonic modulation of dopamine release, a microdialysis study was undertaken, with probes implanted in the substantia nigra and the ipsilateral neostriatum. Perfusion of the substantia nigra with the nonselective antagonist naltrexone (NTX; 1-10 microM), the selective kappa-opoid receptor antagonist, nor-binaltorphimine (nor-BNI; 1-10 microM), and the selective mu-opioid receptor antagonist, D-Pen-Cys-Tyr-D-Trp-Orn-Thr-Pen-Thr-NH(2) (CTOP; 1-10 microM) produced an increase in dopamine release, both in substantia nigra and neostriatum. nor-BNI also produced an increase in dynorphin B release, and a similar effect was observed with the higher concentration of NTX (10 microM). At the higher concentration of NTX and CTOP, an increase in glutamate release was also observed. Perfusion of the neostriatum with NTX, nor-BNI, or CTOP increased striatal dopamine, and dynorphin B release and increased dynorphin B in the ipsilateral substantia nigra. NTX and CTOP, but not nor-BNI, increased striatal glutamate and aspartate release. The kappa-opioid agonist U-50,488H (10 microM) induced a decrease in dopamine levels, both in the substantia nigra and neostriatum, and a paradoxical increase in striatal aspartate levels. Finally, systemic administration of NTX (4 mg/kg s.c.) in awake animals significantly increased striatal dopamine levels. The results suggest that opioid peptides, either dynorphins acting on kappa-opioid receptors or enkephalins acting on mu-opioid receptors, exert tonic inhibition on dopamine and dynorphin B release in both substantia nigra and neostriatum.

Animals↗

PubMed1998

Morphological organization of the globus pallidus-subthalamic nucleus system studied in organotypic cultures.

The morphological organization of the globus pallidus (GP), the subthalamic nucleus (STN), and the pallidosubthalamic projection was studied in organotypic cultures. Coronal slices from the GP, the STN, the striatum (CPu), and the cortex (Cx) were taken from the rat after postnatal days 0-2 and grown for 2 or 5-6 weeks. For analysis, immunocytochemistry against glutamate (GLU), parvalbumin (PV), and calretinin (CR) was combined with confocal microscopy. After 2 weeks in vitro, the STN showed a densely packed, homogeneous GLU-immunoreactive (ir) cell population. Pallidal GLU-ir neurons were heterogeneous, consisting of large-sized weakly GLU-ir neurons and small-sized intensively GLU-ir neurons. After 5-6 weeks in vitro, pallidal axons had radiated from numerous large-sized PV-ir cells and selectively innervated the STN, where they heavily ramified. Cultured STN neurons were not stained for PV; however, multipolar intensely PV-ir neurons were located at the border of the STN with their dendrites oriented towards the STN. Double labeling for PV and CR in both mature cultures and in the adult rat revealed that the culture CR-ir neurons from the GP, the Cpu, and from areas adjacent to the STN were different from cultured PV-ir neurons and their morphologies and distribution corresponded to that in vivo. These results demonstrate that 1) cultured CP and STN neurons display similar morphologies found in in vivo, 2) PV-ir pallidal neurons heavily and selectively innervate the STN; 3) there is a specific class of STN border neurons; and 4) in contrast to the in vivo situation, most cultured STN neurons are PV-negative.

Animals↗

PubMed1998

Modulation of motor behaviour by NMDA- and cholecystokinin-antagonism.

Motor behaviour relies on complex neurochemical interactions in the basal ganglia, in particular the striatum. Antagonistic influences in this region are exerted by afferent projections from, on the one hand, the ventral mesencephalon, utilizing dopamine as a transmitter, and, on the other hand, from the cerebral cortex, signalling by the excitatory amino acid glutamate. The activity in both these neuronal populations appears to be regulated by the neuropeptide cholecystokinin. This article concentrates on interactions between cholecystokinin and glutamate, summarizing some recent morphological, biochemical and behavioural findings. It is suggested that cholecystokinin, acting via the cholecystokininB receptor, potentiates the glutamatergic excitatory input to the striatum.

Animals↗

PubMed1998

Release of endogenous excitatory amino acids in the neostriatum of the rat under physiological and pharmacologically-induced conditions.

There is immunohistochemical evidence suggesting that glutamate (Glu) is released from nerve terminals and acts, via several receptor subtypes, as a major excitatory neurotransmitter in the cortico-striatal pathway of the rat. Aspartate (Asp) is also present in cortico-striatal neurons, but its role as a neurotransmitter has been questioned, since, in contrast to Glu, it has not been demonstrated in presynaptic vesicles. Glu and Asp can be found at submicroM concentrations in the extracellular compartment of most areas of the basal ganglia. Their concentrations are largely regulated by transport mechanisms, but also by a synaptotagmin-dependent exocytotic release, and are sufficiently high to occupy junctional and extrajunctional receptors. We have investigated whether Glu and Asp release in the neostriatum can be selectively modulated by different neuronal systems. Dopamine (DA) and cholecystokinin (CCK) selectively stimulate Asp release, via D1 and CCKB receptor subtypes, respectively. Also opioid kappa-agonists increase Asp release. We propose that the selective modulation of Asp release by D1-, CCKB- and kappa-agonists involves striatal neurons containing Asp, but not Glu. In contrast, local perfusion with the mu-opioid antagonist D-Phe-Cys-Tyr-D-Trp-Orn-Thr-Pen-Thr-NH2 (CTOP) increases both Glu and Asp release. This effect is probably exerted on cortico-striatal terminals, via presynaptic inhibitory mu-receptors. Thus, these results demonstrate that extracellular levels of Glu and Asp are modulated differentially by different neuronal systems, and suggest that in the neostriatum of the rat there are neuronal populations using Glu and/or Asp as messenger(s).

Animals↗

PubMed1998

Sound-evoked efflux of excitatory amino acids in the guinea-pig cochlea in vitro.

We have used the perfused guinea-pig temporal-bone preparation to study the sound-evoked efflux of aspartate and glutamate, which are putative afferent transmitters in the cochlea. The cochlea was stimulated with white noise at 89, 95, and 101 dB SPL. Cochlear function was monitored by recording the endocochlear potential, the cochlear microphonic, and the summating potential. In silence, there was a low basal efflux of both amino acids. A significant and intensity dependent sound-evoked efflux of aspartate was observed at all levels, whereas a significant efflux of glutamate was found only at the 101 dB SPL level. Immunohistochemistry of sections from the organ of corti showed an ubiquitous distribution of glutamate-like immunoreactivity in the sensory organ and ganglion, whereas aspartate-like immunoreactivity was found in the region of the inner hair cells and in the spiral ganglion. In view of these findings, we suggest that not only glutamate, but also aspartate may have a neurotransmitter role in the afferent pathway of the cochlea.

Acoustic Stimulation↗

PubMed1998

Deficient transcription of subunit RPA 40 of RNA polymerase I and III in heart of rats with neonatal asphyxia.

RNA polymerases transcribe nuclear genes for ribosomal RNA thus representing ribosomal biogenesis. RNA polymerase I transcribes class I genes, coding for large ribosomal RNA and is located in the nucleolus. RNA polymerase III transcribes class III genes, those that encode a number of small ribosomal RNA molecules. Both RNA polymerases form ribosomal biogenesis in a concerted action and have a common subunit, RPA40, essential for function and integrity. The aim of our study was to study the influence of hypoxia/asphyxia on transcription of this subunit as deterioration of ribosomal biogenesis may not be compatible with life. To test this hypothesis we used a nonsophisticated model of neonatal asphyxia. Rat pups were exposed to various asphyctic periods up to twenty minutes and heart tissue was taken for the evaluation of mRNA RPA40 levels, pH measurements and histological evaluation of the nucleolus by silver staining. mRNA RPA40 levels gradually decreased with the length of the asphyctic period paralleling the decrease of pH. Silver staining was remarkably decreased at the asphyctic period of 20 minutes. Our findings of decreased transcription of this essential RNA polymerase subunit indicate impairment of the ribosomal RNA synthetizing machinery and the histological findings suggest its structural relevance. This is the first in vivo observation of deteriorated RNA polymerase in asphyxia/hypoxia.

Actins↗

PubMed1997

Short- and long-term effects of perinatal asphyxia on monoamine, amino acid and glycolysis product levels measured in the basal ganglia of the rat.

The effects of perinatal asphyxia on levels of dopamine (DA) and its metabolites, amino acids and glycolysis products, measured in tissue samples from substantia nigra (SN), striatum, ventral tegmental area (VTA), and nucleus accumbens (Acb), were studied 80 min to 8 days after birth with high performance liquid chromatography (HPLC). Furthermore, extracellular levels of DA, amino acids and glycolysis products were measured with in vivo microdialysis in the striatum 40-140 min and 4 weeks after birth. Asphyxia was induced by immersing foetus-containing uterus horns, removed from ready-to-deliver Sprague-Dawley rats, in a water bath at 37 degrees C for various time periods (0-22 min). Spontaneous- and caesarean-delivered pups were used as controls. Perinatal asphyxia led to a decrease in the rate of survival, depending upon the length of the insult. In parallel, lactate (LACT) levels were increased with the length of the insult in all examined brain regions, monitored ex vivo or in vivo immediately after birth. DA, glutamate (GLU) and aspartate (ASP) levels were also increased, mainly in tissue samples taken from the mesencephalon. Only minor changes were observed in tissue samples taken from the telencephalon. However, in experiments with in vivo microdialysis, DA and GLU levels were increased following 20-21 and 21-22 min of perinatal asphyxia, but the effect of K+ depolarisation on extracellular DA and ASP levels was strongly diminished. DA and metabolites increased with development in SN and striatum, with no clear differences between control and asphyctic rats. However, 8 days after birth, it was found that DA levels were increased, alternatively decreased in mesencephalic and telencephalic regions following 20-21 and 21-22 min of perinatal asphyxia, periods associated with 60% and 90% of perinatal mortality, respectively. Furthermore, in microdialysis experiments performed 4 weeks after birth, extracellular DA and its metabolites levels were also increased, alternatively decreased in rats exposed to a 20-21 and 21-22 min perinatal asphyctic insult. In this last group, GLU and ASP levels were also decreased. Furthermore, the effect of K+ depolarisation on DA and ASP levels was strongly decreased in both asphyctic groups. Thus, perinatal asphyxia produces short- and long-term consequences in general metabolism, and induces region-specific changes in several neurotransmitter systems, mainly affecting meso-telencephalic DA systems.

Acute Disease↗

PubMed1997

Perinatal asphyxia-induced changes in rat brain tyrosine hydroxylase-immunoreactive cell body number: effects of nicotine treatment.

Perinatal asphyxia (15-22 min) was induced to male Sprague-Dawley rat pups during the last day of gestation and the surviving pups were sacrificed at 4 weeks of age. Brain sections were stained for tyrosine hydroxylase immunoreactivity and Cresyl violet. With increasing duration of perinatal asphyxia a reduction in the number of tyrosine hydroxylase immunoreactive (TH-IR) nerve cell bodies was found in the locus ceruleus, probably reflecting an increased death of noradrenaline nerve cell bodies. In contrast, perinatal asphyxia (15-20 min) resulted in an increased number of TH-IR nerve cell bodies in the A9 (zona compacta of the substantia nigra) and the A10 (ventral tegmental area) regions of the mesencephalon, probably reflecting an increased survival of dopamine nerve cell bodies. Perinatal asphyxia for longer than 20 min periods reduced the number of TH-IR cell bodies in the 4 week old rat, even below those found in control animals, indicating that when asphyxia is induced for a period leading to almost 100% mortality, a long-term reduction of the number of mesencephalic dopamine neurons is produced. It has previously been shown that a 4 week postnatal nicotine (0.2 micromol/kg per h) treatment counteracts the asphyxia-induced increase in TH-IR cell body number in the substantia nigra and ventral tegmental area. Such nicotine treatment did not influence the reduction in TH-IR cell bodies in the locus ceruleus following 15-20 min of perinatal asphyxia.

Animals↗

PubMed1997

Modulation of catecholamine release by alpha 2-adrenoceptors and I1-imidazoline receptors in rat brain.

The physiological and pharmacological effects of imidazoli(di)ne derivatives, such as clonidine, have been related not only to the interaction with alpha 2-adrenoceptors but also to their activity on non-adrenoceptor sites termed imidazoline receptors. The modulation of catecholamine release by imidazoline drugs was studied by monitoring extracellular levels of norepinephrine (NE), dopamine (DA), 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) with microdialysis in cingulate cortex of rats, with or without irreversible alpha 2-adrenoceptor blockade. NE and DA levels were in the 1 nM range whereas DOPAC and HIVA levels were approximately equal to 100 nM. NE and DA levels were increased when the uptake blocker desipramine (1 microM) or KCl (100 mM) were added to the perfusion medium. Clonidine induced a dose-dependent (0.3-1.2 mg/kg i.p.) decrease in NE (max 61%) and DA (max 40+) levels that was reversed by the alpha 2-adrenoceptor antagonist RX821002. After alpha 2-adrenoceptor irreversible blockade with the alkylating agent N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline (EEDQ), [3H]clonidine binding to alpha 2-adrenoceptors was reduced by 94 +/- 1%. Under such conditions, clonidine elicited a paradoxical dose-dependent (0.6-2.4 mg/kg i.p.) increase of NE (max 56%) without modifications in DA, DOPAC and HVA levels. The stimulatory effect of clonidine was prevented by the imidazoline receptor antagonist idazoxan (10 mg/kg i.p.) but not by RX821002 (5 mg/kg i.p.). In rats pretreated with EEDQ, cirazoline (I1/I2-imidazoline receptor agonist), moxonidine (I1-imidazoline receptor agonist), but not guanabenz (I2-imidazoline receptor agonist) (1.2-2.4 mg/kg i.p.) elicited an increase of NE levels in a similar manner to clonidine (11-82%). Idazoxan also abolished these responses to cirazoline or moxonidine. In contrast to systemic administration, local perfusion of clonidine (10-100 microM) through the microdialysis probe under alpha 2-adrenoceptor alkylating conditions, did not modify extracellular levels of NE and DA suggesting an indirect mechanism. The results demonstrate that clonidine and related imidazoli(di)ne drugs are able not only to inhibit NE release in rat cerebral cortex involving an alpha 2-adrenoceptor mechanism, but also to induce a paradoxical NE release through an indirect extracortical mechanism. The findings evidence that the indirect modulation of NE levels by imidazoline drugs is mainly due to a functional activity on I1-imidazoline receptors.

Animals↗

PubMed1997

Effect of perinatal asphyxia on systemic and intracerebral pH and glycolysis metabolism in the rat.

The effects of perinatal asphyxia on systemic and brain pH and glycolysis metabolism were studied in the rat. Perinatal asphyxia was induced by immersing pup-containing uterus horns, obtained by cesarean section from rats within the last day of gestation, in a water bath at 37 degrees C for various periods of time (0-23 min). Subcutaneous levels of pyruvate (Pyr), lactate (Lact), glutamate (Glu), and aspartate (Asp) were monitored with microdialysis 40-80 min after delivery. In parallel experiments, the pups were sacrificed 40 min after delivery and the heart and brain were removed for measuring pH. Brain (striatum) Pyr, Lact, Glu, and Asp levels were also analyzed. A decrease in the rate of survival was first observed following asphyctic periods longer than 16 min, and no survival could be observed after 22 min of asphyxia. In control (cesarean-delivered) pups, heart and brain pH were 7.36 +/- 0.01 (N = 8) and 7.30 +/- 0.01 (N = 8), respectively. Significant decreases in pH were first observed following 5-6 and 10-11 min of asphyxia, in heart and brain, respectively. In both regions pH decreased along with the length of asphyxia, but a decrease below 7 was only observed in the brain, following asphyctic periods longer than 16 min. A significant increase in subcutaneous Lact levels was first observed following 2-3 min of asphyxia, with a maximum after 20-21 min of asphyxia. In the brain, the increase in Lact levels was delayed compared to that observed in subcutaneous tissue. Pyr and Asp levels increased in subcutaneous tissue following perinatal asphyxia and decreased in brain tissue following > 15 min of asphyxia. Glu levels were increased subcutaneously by moderate (5-16 min) asphyctic periods, but, in the brain, were only transiently increased by 10-11 min of asphyxia. Thus, changes in systemic pH, glycolysis, and excitatory amino acid metabolism are observed following shorter asphyctic periods than are changes in the brain. In particular, increases in subcutaneous Lact levels precede: (i) a decrease in brain pH, (ii) an increase in brain Lact levels, (iii) a decrease in the rate of survival, and, probably, (iv) brain damage. It is suggested that monitoring Lact levels by subcutaneous microdialysis is a useful method for predicting the outcome produced by hypoxic-ischemic insults.

Animals↗

PubMed1997

Perinatal asphyxia induces long-term changes in dopamine D1, D2, and D3 receptor binding in the rat brain.

We have investigated the long-term effects of 15-16 min or 19-20 min of perinatal asphyxia on D1, D2, and D3 receptors (analyzed by quantitative autoradiography) in the mesotelencephalic dopamine systems of the 4-week-old rat. Perinatal asphyxia reduced D1 antagonist binding ([3H]SCH 23390 in the presence of ketanserine) in the accumbens nucleus, the olfactory tubercle, and the substantia nigra and increased D1 agonist binding ([3H]dopamine in the presence of spiperone) in the accumbens nucleus and the olfactory tubercle. No changes in D2 antagonist binding ([123]iodosulpride) were found, whereas D2 agonist binding ([3H]N-propylnorapomorphine, [3H]NPA) was reduced in the posterior part of the caudate-putamen, and following 19-20 min of asphyxia it was also reduced in the accumbens nucleus. D3 agonist binding (R/S-(+/-)-2-(N,N-di[2,3(n)-3H] propylamino)-7-hydroxy-1,2,3,4-tetrahydronaphthalene, [3H]7-OH-DPAT) was increased in the anterior part of the caudate-putamen following 15-16 min but not 19-20 min of asphyxia. The results indicate that perinatal asphyxia reduced the number of D1 receptors and increased D1 agonist affinity in the accumbens nucleus and the olfactory tubercle and reduced the number of D1 receptors in the substantia nigra. The number of D2 receptors was unchanged by asphyxia, whereas the D2 agonist affinity was reduced in the caudate-putamen and in the accumbens nucleus. D3 agonist binding was increased in the caudate-putamen selectively following 15-16 min of asphyxia. In conclusion, asphyxia during birth induces long-term changes in the binding characteristics of dopamine receptors in the mesotelencephalic dopamine systems, which may contribute to previously reported behavioral changes.

Animals↗

PubMed1997

Cholecystokinin-8S increases dynorphin B, aspartate and glutamate release in the fronto-parietal cortex of the rat via different receptor subtypes.

The effect of sulphated cholecystokinin-8 (CCK-8S) on extracellular dynorphin B, aspartate, glutamate and GABA levels in the rat fronto-parietal cortex was investigated with in vivo microdialysis. The peptide was infused through the microdialysis probe trying to mimic local CCK-8S release. Basal levels of dynorphin B were around 20 pM, aspartate 100 nM, glutamate 600 nM and GABA 30 nM. CCK-8S (10 microM) induced a approximately 3-fold increase in extracellular dynorphin B, aspartate and glutamate levels, while GABA levels were only slightly increased. The effect of CCK-8S was restricted to the stimulated neocortex. Systemic pretreatment with the CCKB antagonist, L-365, 260, but not with the CCKA antagonist, L-364, 718, significantly antagonised the effect of CCK-8S on cortical dynorphin B and aspartate release. However, both CCKA and CCKB antagonists inhibited the increase in cortical glutamate levels. Thus, the present results indicate that cortical CCK release exerts a stimulatory modulation on cortical dynorphin B and aspartate release via the CCKB receptor subtype, and on glutamate release via both CCKA and CCKB receptor subtypes. Considering electrophysiological evidence that CCK increases neuronal firing rates in many brain regions, it may be suggested that CCK represents a stimulatory system modulating the function of the neocortex.

Animals↗

PubMed1997

Delayed neuronal death following perinatal asphyxia in rat.

The consequences of perinatal asphyxia on the rat brain were studied 80 min to 8 days after birth with hematoxylin-eosin and in situ DNA double-strand-breaks labeling histochemistry. Asphyxia was induced by immersing fetus-containing uterus horns, removed from ready-to-deliver Sprague-Dawley rats, in a water bath at 37 degrees C for various time periods (0-22 min). Spontaneous- and cesarean-delivered pups were used as controls. Perinatal asphyxia led to a decrease in the rate of survival, depending upon the length of the insult. No gross morphological changes could be seen in the brain of either control or asphyctic pups at any of the studied time points after delivery. However, in all groups, nuclear chromatin fragmentation, corresponding to in situ detection of DNA fragmentation, was observed at different stages. Nuclear fragmentation in control pups showed a specific distribution that appeared to be related to brain maturation, thus indicating programmed cell death. A progressive and delayed increase in nuclear fragmentation was found in asphyctic pups, which was dependent upon the length of the perinatal insult. The most evident effect was seen in frontal cortex, striatum, and cerebellum at postnatal day 8, although changes were also found in ventral-posterior thalamus, at days 1 and 2. Thus, nuclear chromatin fragmentation in asphyctic pups indicates a delayed post-asphyctic neuronal death. The absence of signs of inflammation or necrosis suggests that delayed neuronal cell death following perinatal asphyxia is an active, apoptosis-like phenomenon.

Animals↗

PubMed1997

Excitatory amino acids and monoamines in parahippocampal gyrus and frontal cortical pole of adults with Down syndrome.

Aspartate (ASP), glutamate (GLU), noradrenaline (NA), dopamine (DA) and its acidic metabolites DOPAC and HVA, serotonin (5-HT) and its metabolite 5-HIAA were simultaneously investigated in post-mortem tissue samples from right parahippocampal gyrus (temporal cortex) and frontal cortical pole (frontal cortex) of adults with Down syndrome (DS), and of neurologically healthy controls by use of high performance liquid chromatography (HPLC). In parahippocampal gyrus, ASP, GLU, NA, DOPAC and 5-HT levels were significantly decreased in patients with DS, compared to levels found in control subjects (approximately 50%). No significant changes were observed in frontal pole. ASP and GLU levels were significantly lower in parahippocampal gyrus than in frontal pole of DS, a regional distribution that could not be observed in control subjects. In conclusion, the results of this study suggest that the temporal cortex would be more affected than the frontal cortex in adult patients with DS, a finding in line with reports showing a marked hypometabolism and extensive cell loss in temporal cortex of DS, and with those showing that parahippocampal gyrus abnormality may correlate with the extent of mental retardation affecting this type of patients.

Biogenic Monoamines↗

PubMed1997

On the release of glutamate and aspartate in the basal ganglia of the rat: interactions with monoamines and neuropeptides.

Using highly sensitive analytical procedures, glutamate (Glu), aspartate (Asp) and several putative neurotransmitters and metabolites can be monitored simultaneously in the extracellular space of neostriatum, substantia nigra and cerebral cortex of the rat by in vivo microdialysis. Glu and Asp are found at sub-micromolar concentrations in all investigated brain regions. In order to ascertain their neuronal origin, we have extensively studied the sensitivity of extracellular Glu and Asp levels to: (i) K(+)-depolarization, (ii) Na(+)-channel blockade, (iii) removal of extracellular Ca2+, (iv) depletion of presynaptic vesicles, and (v) integrity of neuronal pathways. The relevance of these criteria for several neurotransmitters monitored simultaneously or in parallel experiments has also been examined. The functional interactions among different neuronal pathways in the basal ganglia are studied by using selective pharmacological treatments, administered systemically, or locally via intracerebral injections or the microdialysis perfusion medium. Immunohistochemical evidence for the existence of Glu and/or Asp neuronal pathways in the basal ganglia of the rat is presented, discussing especially new findings indicating the existence of a Glu-independent Asp system, intrinsic to the neostriatum of the rat. The clinical relevance of these interactions is discussed, focusing on the implications for the treatment of neurodegenerative disorders affecting the basal ganglia.

Animals↗