Biomedical subjects

Jesús M Míguez

Publications and source records attributed to Jesús M Míguez.

16 recordsLinked to original sources

PubMed2006

Evidence for the presence of a glucosensor in hypothalamus, hindbrain, and Brockmann bodies of rainbow trout.

The aim of this study was to evaluate the existence of a glucosensor in different regions of the brain and in the Brockmann bodies (BB) of the rainbow trout, Oncorhynchus mykiss. Five groups (n = 12) of trout were injected intraperitoneally with saline alone (control) or saline-containing bovine glucagon (100 mug/kg), bovine insulin (4 mg/kg), 2-deoxy-d-glucose (100 mg/kg), or d-glucose (500 mg/kg) to promote hyperglycemia (glucagon, d-glucose, 2-deoxy-d-glucose) or hypoglycemia (insulin). Six hours after injection, samples from four brain regions (hypothalamus, telencephalon, hindbrain, and midbrain) and the entire BB were taken. Our results demonstrate within the BB and both the hypothalamus and hindbrain a metabolic response different to that observed in other tissues (midbrain, telencephalon) but similar to that described in tissues known to be glucosensors in mammals. The metabolic responses of these areas to changes in plasma glycemia were characterized by parallel changes in GLUT-2 expression, hexokinase-IV, or glucokinase activity and expression, glycolytic potential, and levels of glycogen and glucose. These changes are similar to those reported in mammalian pancreatic beta-cells and glucose-excited (GE) neurons, two cell types containing glucosensors. This study provides evidence for the presence of glucosensors responsive to hyper- and hypoglycemia in rainbow trout BB, hypothalamus, and hindbrain.

Animals↗

PubMed2006

Daily changes in parameters of energy metabolism in brain of rainbow trout: dependence on feeding.

We assessed the daily patterns of parameters involved in energy metabolism in plasma and brain of rainbow trout. Where daily rhythms were found, we analyzed the potential influence of feeding. Immature rainbow trout were randomly distributed in 3 groups: fish fed for 7 days, fish fasted for 7 days, and fish fasted for 7 days and refed for 4 days. On sampling day, fish of fed and refed groups were fed at 11.00 h, and all fish were sampled from each treatment group using the following time schedule: 14.00, 18.00, 21.00, 00.00, 04.00, 07.00, 10.00 and 14.00 h. The results obtained from metabolic parameters assessed in plasma and brain can be grouped into three different categories, such as (i) those displaying no 24 h changes in fed fish such as plasma lactate, protein or acetoacetate levels, as well as brain amino acid and protein levels, and lowKm(glucose) hexokinase, and aspartate aminotransferase activities, (ii) those displaying 24 h changes that were apparently dependent on feeding since they disappeared in fasted fish such as the case of plasma cortisol, glucose and triglyceride levels, as well as brain glycogen, glucose, and lactate levels, and pyruvate kinase and hexokinase IV activities, and (iii) those parameters displaying 24 h changes apparently not dependent on feeding such as plasma amino acids, brain acetoacetate levels as well as several enzyme activities measured in brain such as glucose 6-phosphate dehydrogenase, alpha-glycerophosphate dehydrogenase, glutamate dehydrogenase, and lactate dehydrogenase-oxidase. In general, 24 h changes dependent on feeding indicate an increased use of glucose in brain several hours post-feeding whereas those changes not dependent on feeding were characterized by reduced levels/activity at the night period suggesting a metabolic depression in brain during darkness.

Acetoacetates↗

PubMed2006

Effects of acute and prolonged naphthalene exposure on brain monoaminergic neurotransmitters in rainbow trout (Oncorhynchus mykiss).

We have shown previously that acute (1 to 6 h) and prolonged (1 to 5 days) exposure of rainbow trout to naphthalene resulted in decreased plasmatic cortisol and 17-beta-estradiol levels. In order to elucidate the mechanisms through which naphthalene might disrupt endocrine regulation, the present study investigated whether brain monoaminergic neurotransmitters are altered by the action of this polycyclic aromatic hydrocarbon. In a first experiment, immature rainbow trout were injected with vegetable oil alone or containing naphthalene (10 and 50 mg/kg, i.p.), and sacrificed 1, 3 and 6 h after treatment. In a second experiment, slow-coconut oil implants alone or containing naphthalene (doses of 10 and 50 mg/kg) were i.p. located and fish sacrificed 1, 3 and 5 days after treatment. Levels of dopamine (DA), 3,4-dihydroxyphenylacetic acid (DOPAC), serotonin (5-HT), 5-hydroxyindoleacetic acid (5-HIAA) and noradrenaline (NA) were measured in several brain regions by HPLC. The results show that short-term naphthalene increases DA and 5-HT contents in hypothalamus and telencephalon, but differentially alter contents of the acid metabolites. Implants with naphthalene reduced DA content in hypothalamus and preoptic region but increased in telencephalon. 5-HT metabolism was decreased in hypothalamus, preoptic region, pituitary and brain stem after 3 to 6 days of treatment. In addition, the levels of NA were increased in hypothalamus and telencephalon after acute treatment and in hypothalamus and preoptic area after several days of exposure to naphthalene. These data suggest that brain neurotransmitter systems are sensitive to polycyclic aromatic hydrocarbons and could represent a target of the naphthalene-induced neuroendocrine disruption.

3,4-Dihydroxyphenylacetic Acid↗

PubMed2006

Interactive effects of naphthalene treatment and the onset of vitellogenesis on energy metabolism in liver and gonad, and plasma steroid hormones of rainbow trout Oncorhynchus mykiss.

The purpose of the study was to assess in female fish the possible interaction between treatment with a polycyclic aromatic hydrocarbon (PAH) like naphthalene and the onset of vitellogenesis. In a first experiment, female rainbow trout (Oncorhynchus mykiss) at stages 2-3 (previtellogenesis) or 4 (early vitellogenesis) were intraperitoneally injected (2 microl g(-1)) with vegetable oil alone (control) or containing naphthalene (50 mg kg(-1)) to be sampled 3 h later. A second experiment was similarly designed but using fish intraperitoneally implanted (10 microl g(-1)) with slow-release coconut oil implants alone (control) or containing 50 mg naphthalene kg(-1) body mass that were sampled 3 days after injection. On each sampling time, plasma levels of cortisol and 17beta-estradiol, and several metabolic parameters in plasma, liver and gonad were assessed. In controls, early vitellogenic fish compared with previtellogenic fish displayed changes that in some cases are confirmatory of previous studies whereas in other cases provide new information in plasma (increased amino acid levels), liver (decreased capacity for exporting glucose and reduced amino acid levels) and gonad (decreased amino acid levels). Naphthalene treatment produced in previtellogenic fish decreased 17beta-estradiol levels in plasma, increased plasma glucose or decreased liver gluconeogenic capacity whereas no major effects were noticed on parameters involved in lipid, amino acid and lactate metabolism. Differential effects of naphthalene treatment were noticed in early vitellogenic fish such as decreased 17beta-estradiol and glucose levels in plasma, increased hexokinase and glucokinase and lack of changes in fructose 1,6-bisphosphatase activities in liver, and a lower decrease of amino acid levels in gonad. Those alterations produced by naphthalene treatment resulted in a decreased capacity for covering the energy demand of vitellogenesis in liver and gonad that could contribute to a delay and/or impairment of the onset of maturation.

Amino Acids↗

PubMed2006

Influence of testosterone administration on osmoregulation and energy metabolism of gilthead sea bream Sparus auratus.

The osmoregulatory and metabolic role of testosterone (T) in the euryhaline teleost Sparus auratus was examined. Fish were implanted with a slow-release coconut oil implant alone (control) or containing T (2 or 5microgg(-1) body weight) and sampled 1, 3, and 7 days after implantation. Gill Na(+),K(+)-ATPase activity increased in fish treated with the lower dose of T after 7 days of treatment. Kidney Na(+),K(+)-ATPase activity enhanced at first day post-implantation in the group treated with the higher dose of T but the values diminished by day 3. Plasma levels of metabolites (glucose, lactate, triglyceride, and protein) increased after T treatment. This higher availability of plasma metabolites was reflected in several metabolic changes within different tissues of T-treated fish such as (i) increased glycogen levels and capacity for gluconeogenesis, ketogenesis, glucose exporting, and amino acid catabolism in the liver, (ii) enhanced lipogenic capacity in the gills, (iii) increased glycogen levels and capacity for oxidizing amino acids in the kidney, and (iv) enhanced levels of glycogen, aceotacetate, glucose and triglycerides, and higher capacity of phosphorylating glucose in the brain. These results provide evidence regarding an osmoregulatory and metabolic role for T in S. auratus that could be related to changes in both processes during sexual maturation.

Animals↗

PubMed2006

Osmoregulatory and metabolic changes in the gilthead sea bream Sparus auratus after arginine vasotocin (AVT) treatment.

The influence of arginine vasotocin (AVT) on osmoregulation and metabolism in gilthead sea bream Sparus auratus was evaluated by two experimental approaches. In the first, seawater (SW, 36 ppt)-acclimatized fish were injected intraperitoneally with vehicle (vegetable oil) or two doses of AVT (0.5 and 1 microg/g body weight). Twenty-four hours later, eight fish from each group were sampled; the remaining fish were transferred to low saline water (LSW, 6 ppt, hypoosmotic test), SW (transfer control), and hypersaline water (HSW, 55 ppt, hyperosmotic test). After another 24h (48-h post-injection), fish were sampled. The only significant effect observed was the increase of sodium levels in AVT-treated fish transferred to HSW. In the second experiment, fish were injected intraperitoneally with slow-release vegetable oil implants (mixture 1:1 of coconut oil and seeds oil) alone or containing AVT (1 microg/g body weight). After 3 days, eight fish from each group were sampled; the remaining fish were transferred to LSW, SW, and HSW as above, and sampled 3 days later (i.e. 6 days post-injection). In the AVT-treated group transferred from SW to SW, a significant increase vs. control was observed in gill Na(+),K(+)-ATPase activity. Kidney Na(+),K(+)-ATPase activity decreased in the AVT-treated group transferred to LSW and no changes were observed in the other groups. These osmoregulatory changes suggest a role for AVT during hyperosmotic acclimation based on changes displayed by gill Na(+),K(+)-ATPase activity. AVT treatment increased plasma cortisol levels in fish transferred to LSW and HSW. In addition, AVT treatment affected parameters of carbohydrate, lipid, amino acid, and lactate metabolism in plasma and tissues (gills, kidney, liver, and brain). The most relevant effects were the increased potential of liver for glycogen mobilization and glucose release resulting in increased plasma levels of glucose in AVT-treated fish transferred to LSW and HSW. These changes may be related to the energy repartitioning process occurring during osmotic adaptation of S. auratus to extreme environmental salinities and could be mediated by increased levels of cortisol in plasma.

Acclimatization↗

PubMed2006

Growth hormone and prolactin actions on osmoregulation and energy metabolism of gilthead sea bream (Sparus auratus).

The gilthead sea bream (Sparus auratus) is an euryhaline fish where prolactin (PRL) and growth hormone (GH) play a role in the adaptation to different environmental salinities. To find out the role of these pituitary hormones in osmoregulation and energy metabolism, fish were implanted with slow release implants of ovine GH (oGH, 5 microg g(-1) body mass) or ovine prolactin (oPRL, 5 microg g(-1) body mass), and sampled 7 days after the start of the treatment. GH increased branchial Na(+),K(+)-ATPase activity and decreased sodium levels in line with its predicted hypoosmoregulatory action. GH had metabolic effects as indicated by lowered plasma protein and lactate levels, while glucose, triglycerides and plasma cortisol levels were not affected. Also, GH changed liver glucose and lipid metabolism, stimulated branchial and renal glucose metabolism and glycolytic activity, and enhanced glycogenolysis in brain. PRL induced hypernatremia. Furthermore, this hormone decreased liver lipid oxidation potential, and increased glucose availability in kidney and brain. Both hormones have opposite osmoregulatory effects and different metabolic effects. These metabolic changes may support a role for both hormones in the control of energy metabolism in fish that could be related to the metabolic changes occurring during osmotic acclimation.

Acclimatization↗

PubMed2006

Naphthalene treatment alters liver intermediary metabolism and levels of steroid hormones in plasma of rainbow trout (Oncorhynchus mykiss).

To assess the effects of naphthalene on liver intermediary metabolism and plasma steroid hormones, immature female rainbow trout (Oncorhynchus mykiss), in a first experiment, were intraperitoneally injected (2 microLg(-1)) with vegetable oil alone (control) or containing naphthalene (10 and 50 mgkg(-1)) and returned to their tanks. At 1, 3, and 6h after injection, eight fish were sampled from each group. A second experiment was similarly designed but used fish intraperitoneally implanted (10 microLg(-1)) with slow-release coconut oil implants alone (control) or containing naphthalene at doses of 10 and 50 mgkg(-1) body weight that were sampled 1, 3, and 5 days after injection. At each sampling time, plasma hormone levels (cortisol and 17beta-estradiol) and metabolic parameters in plasma (glucose and lactate) and liver (glucose, lactate, and glycogen levels and HK, GK, GPase, GDH, FBPase, and PK activities) were assessed. Changes described for both hormonal systems resulted in a decrease in plasma levels of cortisol and 17beta-estradiol. Changes observed in intermediary metabolism described effects in several pathways of liver energy metabolism due to naphthalene. These changes can be summarized as increased glycogenolysis, use of exogenous glucose, and glycolysis and decreased gluconeogenesis. The increased energy production in liver suggested by these changes can be related to the increased detoxification activity known to occur in liver after PAH exposure, and can be also related directly or indirectly to the changes observed in the levels of plasma steroids.

Animals↗

PubMed2005

Interactive effects of high stocking density and food deprivation on carbohydrate metabolism in several tissues of gilthead sea bream Sparus auratus.

The influence of high stocking density (HSD) and food deprivation was assessed on carbohydrate metabolism of several tissues of gilthead sea bream Sparus auratus for 14 days. Fish were randomly assigned to one of four treatments: (1) fed fish under normal stocking density (NSD) (4 kg m(-3)); (2) fed fish under HSD (70 kg m(-3)); (3) food-deprived fish under NSD; and (4) food-deprived fish under HSD. After 14 days, samples were taken from the plasma, liver, gills, kidney and brain for the assessment of plasma cortisol, levels of metabolites and the activity of several enzymes involved in carbohydrate metabolism. HSD conditions alone elicited important changes in energy metabolism of several tissues that in some cases were confirmatory (5-fold increase in plama cortisol, 20% increase in plasma glucose, 60% decrease in liver glycogen and 20% increase in gluconeogenic potential in the liver) whereas in others provided new information regarding metabolic adjustments to cope with HSD in the liver (100% increase in glucose phosphorylating capacity), gills (30% decrease in capacity for phosphorylating glucose), kidney (80% increase in the capacity of phosphorylating glucose) and brain (2.5-fold increase in ATP levels). On the other hand, food deprivation alone resulted in increased plasma cortisol, and metabolic changes in the liver (enhanced gluconeogenic and glycogenolytic potential of 13% and 18%, respectively) and brain (10% increase in glycolytic capacity), confirmatory of previous studies, whereas new information regarding metabolic adjustments during food deprivation was obtained in the gills and kidney (decreased lactate levels in both tissues of 45% and 55%, respectively). Furthermore, the results obtained provided, for the first time in fish, information indicating that food deprivation increased the sensitivity of gilthead sea bream to the stress induced by HSD compared with the fed controls, as demonstrated by increased plasma cortisol levels (50% increase vs. fed fish) and a further increase in the capacity to export glucose mobilized from liver glycogen stores (70% decrease vs. fed fish). These results lend support for a cumulative effect of both stressors on plasma cortisol and parameters assessed on carbohydrate metabolism in the present experiments, and provide information regarding reallocation of metabolic energy to cope with simultaneous stressors in fish.

Animals↗

PubMed2005

Actions of growth hormone on carbohydrate metabolism and osmoregulation of rainbow trout (Oncorhynchus mykiss).

Rainbow trout Oncorhynchus mykiss were injected intraperitoneally with slow-release implants of vegetable oil alone or containing ovine growth hormone (oGH) (2 and 5 microgg(-1) body weight), and sampled after 5 days to assess the simultaneous effects of GH on both osmoregulation and carbohydrate metabolism. An enhanced hypoosmoregulatory capacity of oGH-implanted fish is suggested by the increase observed in gill Na+,K+-ATPase activity, and the decrease observed in plasma ion concentration (Na+ and Cl-) and osmolality. GH treatment also elicited increased plasma glucose levels and metabolic changes in liver, gills, kidney, and brain. Major metabolic changes elicited by GH treatment included (1) decreased glycolytic potential and capacity for exporting glucose in liver, (2) enhanced glycogenolytic potential and capacity for use of exogenous glucose in gills and kidney, as well as increased glycolytic capacity in the later tissue, and (3) enhanced glycogenolytic and glycolytic capacities in brain. These metabolic changes elicited by GH treatment support a role for GH in the control of carbohydrate metabolism in salmonids that could be related either to the metabolic changes occurring during osmotic acclimation in nature (a process in which changes in GH levels and carbohydrate metabolism have both been reported) or to metabolic changes associated with growth.

Animals↗

PubMed2005

Indoleamines and 5-methoxyindoles in trout pineal organ in vivo: daily changes and influence of photoperiod.

This study describes the diel rhythms in several indoleamines, melatonin, and related 5-methoxyindoles in the pineal organ of rainbow trout in vivo. In addition, the effect of different photoperiod conditions was evaluated. Melatonin levels displayed clear daily rhythms in the pineal organ of rainbow trout kept experimentally under long (LD 16:08), neutral (LD 12:12), and short (LD 08:16) photoperiods. Duration of melatonin signal was dependent on the night length of prevailing photoperiod, while peak amplitude was higher when lengthening the photoperiod. Significant daily rhythms in 5-HT content, the precursor of melatonin synthesis, were found in neutral and short photoperiod with increases of the amine content just after the light-dark interphase and decreases in the middle of the night, which were more important under short photoperiod. In contrast, no significant 24-h cyclic variation was found in pineal 5-HT content under long photoperiod. Daily profiles in the content of the main 5-HT oxidative metabolite, the 5-hydroxyindoleacetic acid (5-HIAA), outlined those of the amine precursor. The chronograms of both aminergic compounds contrast with those of 5-hydroxytryptophan content, which displayed a net tendency to increase at night. This study also provides evidence for the existence of daily cyclic changes in the content of 5-methoxytryptamine (5-MT), 5-methoxyindoleacetic acid (5-MIAA), and 5-methoxytryptophol (5-MTOL) in trout pineal organ, which were also dependent on photoperiod. The 24-h profiles in 5-MT content correlated well with those of 5-HT, showing a peak at the first hour of darkness in all photoperiodic conditions, and a decay at midnight only in both neutral and long photoperiods. Similarly, the content of 5-MTOL also displayed high values during the day-night transition in trout kept under neutral and long photoperiods, followed by a slow decay all along the night. Finally, levels of 5-MIAA increased in all photoperiods when lights were turned off, being this nocturnal increase maximal in fish kept under LD 16:08. These results suggest that light-dark cycle modulates daily rhythms in pineal indoles and non-melatonin 5-methoxyindoles by acting mainly through the melatonin synthesis activity, which limits the availability of 5-HT for the oxidative and direct methylation pathways. In addition, it seems that a nocturnally increased synthesis of 5-HT might be a requirement for the optimal formation of melatonin and other 5-methoxyindoles in the pineal organ when trout remain under short photoperiods.

5-Methoxytryptamine↗

PubMed2005

Time course of osmoregulatory and metabolic changes during osmotic acclimation in Sparus auratus.

Changes in different osmoregulatory and metabolic parameters over time were assessed in gills, kidney, liver and brain of gilthead sea bream Sparus auratus transferred either from seawater (SW, 38 p.p.t.) to hypersaline water (HSW, 55 p.p.t.) or from SW to low salinity water (LSW, 6 p.p.t.) for 14 days. Changes displayed by osmoregulatory parameters revealed two stages during hyperosmotic and hypo-osmotic acclimation: (i) an adaptive period during the first days of acclimation (1-3 days), with important changes in these parameters, and (ii) a chronic regulatory period (after 3 days of transfer) where osmotic parameters reached homeostasis. From a metabolic point of view, two clear phases can also be distinguished during acclimation to hyperosmotic or hypo-osmotic conditions. The first one coincides with the adaptive period and is characterized by enhanced levels of plasma metabolites (glucose, lactate, triglycerides and protein), and use of these metabolites by different tissues in processes directly or indirectly involved in osmoregulatory work. The second stage coincides with the chronic regulatory period observed for the osmoregulatory parameters and is metabolically characterized in HSW-transferred fish by lower energy expenditure and a readjustment of metabolic parameters to levels returning to normality, indicative of reduced osmoregulatory work in this stage. In LSW-transferred fish, major changes in the second stage include: (i) decreased glycolytic potential, capacity for exporting glucose and potential for amino acid catabolism in liver; (ii) enhanced use of exogenous glucose through glycolysis, pentose phosphate and glycogenesis in gills; (iii) increased glycolytic potential in kidney; and (iv) increased glycogenolytic potential and capacity for use of exogenous glucose in brain.

Acclimatization↗

PubMed2004

GABA modulates day-night variation in melatonin levels in the cerebral ganglia of the damselfly Ischnura graellsii and the grasshopper Oedipoda caerulescens.

The relationship between daily rhythms in GABA content and melatonin (MEL) content, as well as the effect of GABA treatment during either the day time and night time phases on MEL levels and N-acetyltransferase (NAT) activity, were studied in the brains of two insect species, the grasshopper Oedipoda caerulescens and the damselfly Ischnura graellsii. In O. caerulescens, levels of GABA in the optic lobes showed significant daily variation, with a marked increase during the light-to-dark transition period. In contrast, in the brain of I. graellssi, two daily peaks in GABA levels were observed, during the light-to-dark and the dark-to-light transition periods. In both insects the maximal levels of GABA occurred 4-6 h in advance of the nocturnal MEL peak, which was associated with a reduction in GABA levels. In both insects, treatment with GABA (1 microg/microl, intracranial injection) during the night was followed by a significant reduction in melatonin levels and NAT activity. In contrast, GABA administered during the day time increased brain MEL levels and synthesis. These data suggest that GABA acts as a modulator of light/dark-dependent melatonin synthesis in the insect brain.

Acetyltransferases↗

PubMed2004

Osmoregulatory action of 17beta-estradiol in the gilthead sea bream Sparus auratus.

The osmoregulatory action of 17beta-estradiol (E2) was examined in the euryhaline teleost Sparus auratas. In a first set of experiments, fish were injected once with vegetable oil containing E2 (1, 2 and 5 microg/g body weight), transferred 12h after injection from sea water (SW, 38 ppt salinity) to hypersaline water (HSW, 55 ppt) or to brackish water (BW, 5 ppt salinity) and sampled 12h later (i.e. 24 h post-injection). In a second experiment, fish were injected intraperitoneally with coconut oil alone or containing E2 (10 microg/g body weight) and sampled after 5 days. In the same experiment, after 5 days of treatment, fish of each group were transferred to HSW, BW and SW and sampled 4 days later (9 days post-implant). Gill Na+,K+ -ATPase activity, plasma E2 levels, plasma osmolality, and plasma levels of ions (sodium and calcium), glucose, lactate, protein, triglyceride, and hepatosomatic index were examined. Transfer from SW to HSW produced no significant effects on any parameters assessed. E2 treatment did not affect any parameter. Transfer from SW to BW resulted in a significant decrease in plasma osmolality and plasma sodium but did not affect gill Na+,K+ -ATPase activity. A single dose of E2 attenuated the decrease in these parameters after transfer from SW to BW, but was without effect on gill Na+,K+ -ATPase activity. An implant of E2 (10 microg/g body weight) for 5 days significantly increased plasma calcium, hepatosomatic index, plasma metabolic parameters, and gill Na+,K+ -ATPase activity. In coconut oil-implanted (sham) fish, transfer from SW to HSW or BW during 4 days significantly elevated gill Na+,K+ -ATPase. Gill Na+,K+ -ATPase activity remained unaltered after transfer of E2-treated fish to HSW or BW. However, in E2-treated fish transferred from SW to SW (9 days in SW after E2-implant), gill Na+,K+ -ATPase activity decreased with respect to HSW- or BW-transferred fish. Shams transferred to HSW showed increased levels of lactate, protein, and trygliceride in plasma, while those transferred to BW only displayed increased trygliceride levels. E2-treated fish transferred to HSW showed higher protein levels without any change in other plasmatic parameters, while those transferred to BW displayed elevated plasma glucose levels but decreased osmolality and protein levels. These results substantiate a chronic stimulatory action of E2 on gill Na+,K+ -ATPase activity in the euryhaline teleost Sparus auratas.

Analysis of Variance↗

PubMed2002

Somatodendritic action of pindolol to attenuate the paroxetine-induced decrease in serotonin release from the rat ventral hippocampus: a microdialysis study.

We used intracerebral microdialysis to study the role of raphe and presynaptic serotonin (5-HT) autoreceptors in the effect of the selective 5-HT reuptake inhibitor, paroxetine, on 5-HT release from ventral hippocampus of anaesthetised rats. In addition, we have tested the ability of pindolol, a non-selective beta-adrenergic/5-HT(1A) receptor antagonist, to alter the response of hippocampal 5-HT to paroxetine. Doses of paroxetine with maximal effects were near to three-fold less effective when administered systemically than after local infusion at increasing extracellular 5-HT in ventral hippocampus. Moreover, systemic paroxetine treatment resulted in a marked decrease of the extracellular 5-HT in the hippocampus when 5-HT reuptake was blocked with paroxetine 3 microM applied locally, thereby evidencing that systemic treatment induced a decrease of 5-HT release in the neuronal terminal. A similar drop was observed when paroxetine 3 microM was perfused into the median raphe, a region that contains the cell bodies of the neurons innervating the ventral hippocampus. Racemic (+/-)-pindolol (10 mg/kg, s.c.) completely blocked the paroxetine-induced decrease in 5-HT release from rat hippocampus. In addition, the infusion into median raphe of (-)-pindolol, the isoform with highest antagonist activity, at concentrations of 10 microM and 100 microM was able to partially block the decrease of hippocampal 5-HT release after systemic paroxetine. However, perfusion of (-)-pindolol into the hippocampus was without effect on local 5-HT release. These data suggest that pindolol acts preferentially through the blockade of somatodendritic 5-HT(1A) autoreceptors to restore the decline in 5-HT outflow in rat forebrain following systemic administration of selective 5-HT reuptake inhibitors.

Adrenergic beta-Antagonists↗

PubMedDate not supplied

Intracerebroventricular injections of noradrenaline affect brain energy metabolism of rainbow trout.

To assess the role of noradrenaline (NA) as a possible regulator of brain energy metabolism in teleost fish, the impact of increased noradrenaline levels within the brain on several parameters of energy metabolism was assessed in rainbow trout brain. Accordingly, two different doses of noradrenaline, producing increases in brain NA levels comparable to those occurring in several physiological processes in nature, were selected. In a subsequent set of three different experiments, fish were intracerebroventricularly injected with 1 microL 100 g(-1) body weight of Cortland saline alone (control) or containing NA (5 nmol NA and 10 nmol NA); after 30 min, brain and plasma samples were taken to assess changes in parameters of energy metabolism due to NA treatment. The results obtained clearly show dose-dependent changes in NA-treated fish in several parameters, including decreased glycogen and ATP levels, increased lactate and pyruvate levels, decreased fructose 1,6-bisphosphatase activity, and increased pyruvate kinase and lactate dehydrogenase activities. Altogether, the present experiments show for the first time in a teleost fish evidence supporting that increased noradrenaline levels in the brain elicit metabolic changes in the brain (enhanced glycogenolysis and glycolysis), resulting in an increased energy demand. These metabolic changes may be related to those occurring under several physiological conditions in nature such as hypoxia, in which increased energy demand and increased noradrenaline levels occur in the brain simultaneously.

Animals↗