Long-term prognosis of patients with major depression and silent cerebral infarction.

OBJECTIVE: Many studies have examined the effects of cerebrovascular changes on treatment response in geriatric depression. However, few such studies have examined the relationship between cerebrovascular changes and long-term prognosis. We examined the effects of cerebrovascular changes on the course of geriatric depressive symptoms, dementia rates, and mortality over a follow-up period of approximately 10 years. METHOD: Participants were 84 patients with major depression (age of onset over 50 years); patients suffering from strokes, neurological disorders, and other psychiatric disorders were excluded. Magnetic resonance imaging findings were used to classify all patients into silent cerebral infarction (SCI)-positive (n = 37) or SCI-negative groups (n = 47). Prognoses were ascertained using a review of clinical charts and mailed questionnaires. RESULTS: Only 5% of patients with SCI were able to maintain remission whereas 36% of patients without SCI were able to do so. Total duration of depressive episodes was significantly longer in the SCI-positive group than in the SCI-negative group. SCI was also associated with a higher risk of dementia. CONCLUSION: The results of this long-term follow-up study demonstrate that the presence of SCI is associated with a relatively poor prognosis in geriatric depression.

Neonatal tactile stimulation reverses the effect of neonatal isolation on open-field and anxiety-like behavior, and pain sensitivity in male and female adult Sprague-Dawley rats.

It is well known that early life events induce long-lasting psychophysiological and psychobiological influences in later life. In rodent studies, environmental enrichment after weaning prevents the adulthood behavioral and emotional disturbances in response to early adversities. We compared the behavioral effect of neonatal isolation (NI) with the effect of NI accompanied by tactile stimulation (NTS) to determine whether NTS could reverse or prevent the effects of NI on the adulthood behavioral and emotional responses to environmental stimuli. In addition, we also examined the sex difference of the NTS effect. Measurements of body weights, an open-field locomotor test, an elevated plus maze test, a hot-plate test, and a contextual fear-conditioning test were performed on postnatal day 60. As compared with rats subjected to NI, rats subjected to NTS showed significantly higher activity and exploration in the open-field locomotor test, lower anxiety-like behavior in the elevated plus maze test, and significantly prolonged latencies in the hot-plate test, and this effect was equal among males and females. In the contextual fear-conditioning test, whereas NTS significantly reduced the enhanced freezing time due to NI in females, no significant difference in the freezing time between NI and NTS was found in males. These findings indicate that adequate tactile stimulation in early life plays an important role in the prevention of disturbances in the behavioral and emotional responses to environmental stimuli in adulthood induced by early adverse experiences.

Glucocorticoid receptor activation is involved in producing abnormal phenotypes of single-prolonged stress rats: a putative post-traumatic stress disorder model.

Post-traumatic stress disorder (PTSD) is a stress-related mental disorder caused by traumatic experience, and presents with characteristic symptoms, such as intrusive memories, a state of hyperarousal, and avoidance, that endure for years. Single-prolonged stress (SPS) is one of the animal models proposed for PTSD. Rats exposed to SPS showed enhanced inhibition of the hypothalamo-pituitary-adrenal (HPA) axis, which has been reliably reproduced in patients with PTSD, and increased expression of glucocorticoid receptor (GR) in the hippocampus. In this study, we characterized further neuroendocrinologic, behavioral and electrophysiological alterations in SPS rats. Plasma corticosterone recovered from an initial increase within a week, and gross histological changes and neuronal cell death were not observed in the hippocampus of the SPS rats. Behavioral analyses revealed that the SPS rats presented enhanced acoustic startle and impaired spatial memory that paralleled the deficits in hippocampal long-term potentiation (LTP) and depression. Contextual fear memory was enhanced in the rats 1 week after SPS exposure, whereas LTP in the amygdala was blunted. Interestingly, blockade of GR activation by administering 17-beta-hydroxy-11-beta-/4-/[methyl]-[1-methylethyl]aminophenyl/-17-alpha-[prop-1-ynyl]estra-4-9-diene-3-one (RU40555), a GR antagonist, prior to SPS exposure prevented potentiation of fear conditioning and impairment of LTP in the CA1 region. Altogether, SPS caused a number of behavioral changes similar to those described in PTSD, which marks SPS as a putative PTSD model. The preventive effects of a GR antagonist suggested that GR activation might play a critical role in producing the altered behavior and neuronal function of SPS rats.

Glutathione S-transferase gene polymorphisms in Japanese patients with rheumatoid arthritis.

OBJECTIVE: To investigate the role of polymorphisms of the glutathione S-transferase M1 (GSTM1), GSTT1, and GSTP1 genes in determining susceptibility to rheumatoid arthritis (RA) and association with the clinical features. METHODS: Polymorphisms of the GSTM1, GSTT1, and GSTP1 genes in 108 Japanese patients with RA and in 143 healthy controls were analyzed by polymerase chain reaction (PCR) or PCR-restriction fragment length polymorphism. RESULTS: The frequency of the GSTM1 null genotype was significantly higher among RA patients than among control subjects (60.2% and 44.1%, respectively. P = 0.011). Moreover, the female patients with GSTM1 homozygous null genotype showed significantly higher serum MMP-3 level than the female patients with non-null genotype (P = 0.030). Frequencies of the GSTT1 and GSTP1 gene polymorphism were not different between RA patients and controls. CONCLUSION: The GSTM1 homozygous null genotype could be a genetic factor that determines susceptibility to RA and may have influence on the disease process.

Acetylcholinesterase activities and monoamine metabolite levels in the cerebrospinal fluid of patients with Alzheimer's disease.

We measured cholinesterase (ChE) activity and monoamine metabolite levels in the cerebrospinal fluid (CSF) of 22 patients with early-onset Alzheimer type dementia (Alzheimer's disease; AD) and of 32 controls. Acetylcholinesterase (AChE) activity, 5-hydroxyindoleacetic acid (5-HIAA), and homovanillic acid (HVA) levels were significantly lower in AD patients than in controls. However, there was an overlap in values of each CSF parameter. The measurement of various CSF parameters rather than one alone was more useful as a diagnostic aid. CSF ChE activities correlated with scores on the GBS rating scale, Hasegawa dementia scale, and Wechsler Adult Intelligence Scale, but the monoamine metabolite levels did not. Although cholinergic and monoaminergic deficits may coexist in AD patients, cholinergic deficits tend to be more often associated with cognitive decline than the monoaminergic deficits.

Chronic antidepressant treatment down-regulates the induction of c-fos mRNA in response to acute stress in rat frontal cortex.

The present study examines the influence of electroconvulsive seizure (ECS), as well as several antidepressant drug treatments, on the induction of c-fos mRNA in response to acute restraint stress. Acute (45-minute) restraint stress resulted in five- to sixfold elevation of c-fos mRNA levels in rat frontal cortex. Chronic administration of ECS significantly decreased the induction of c-fos mRNA levels in response to acute restraint stress, and this effect was observed after chronic (6 to 9 days) but not acute (1 or 3 days) of ECS treatment. In addition, c-fos induction in response to acute restraint stress was down-regulated by chronic, but not acute, administration of tranylcypromine or imipramine, two drugs that nonselectively increase synaptic levels of norepinephrine and serotonin by inhibition of monoamine oxidase or neurotransmitter reuptake, respectively. Moreover, chronic administration of desipramine or sertraline, selective re-uptake inhibitors of norepinephrine, or serotonin, respectively, also significantly down-regulated the induction of c-fos mRNA in response to restraint stress. Chronic administration of ECS, tranylcypromine, or imipramine also decreased stressed-induced levels of NGFI-A mRNA, another immediate early gene transcription factor, whereas levels of c-jun mRNA were not influenced by either stress or antidepressant treatments. The results demonstrate that chronic, but not acute, administration of ECS and several different classes of antidepressant drugs down-regulates stress-induced levels of c-fos mRNA, suggesting that this effect may be a common, postreceptor action of antidepressant treatments.

Administration of a cAMP phosphodiesterase 4 inhibitor enhances antidepressant-induction of BDNF mRNA in rat hippocampus.

The influence of two selective phosphodiesterase 4 (PDE4) inhibitors, rolipram and Ro 20-1724, on the induction of BDNF mRNA by antidepressant treatment was examined. Coadministration of rolipram or Ro 20-1724 with an antidepressant (either desipramine or Org 4428) for 21 d resulted in a significant induction of BDNF mRNA in hippocampus relative to administration of vehicle. Coadministration of a PDE4 inhibitor with an antidepressant for 7 or 14 d also increased levels of BDNF mRNA. In contrast, acute coadministration did not influence levels of BDNF mRNA. In situ hybridization analysis demonstrated that the induction of BDNF mRNA in response to the repeated coadministration paradigm occurs in the dentate gyrus granule and CA1 and CA3 pyramidal cell layers of hippocampus. These findings demonstrate that coadministration shortens the time required for the upregulation of BDNF mRNA, supporting the possibility that this treatment may provide an effective therapy for major depression.

Differential changes in messenger RNA expressions and binding sites of neuropeptide Y Y1, Y2 and Y5 receptors in the hippocampus of an epileptic mutant rat: Noda epileptic rat.

The anti-convulsive effects of neuropeptide Y have been suggested in several animal models of epilepsy. We have found the sustained increase of neuropeptide Y contents and the seizure-induced elevation of hippocampal messenger RNA in a novel spontaneous epileptic mutant rat: Noda epileptic rat. In the present study, we investigated the change of neuropeptide Y Y1 and Y2 receptor messenger RNA expressions and binding sites in the hippocampus following a spontaneous generalized tonic-clonic seizure of Noda epileptic rat. Furthermore, the binding sites of a more recently isolated receptor subtype, neuropeptide Y Y5 receptors, were also evaluated by receptor autoradiography. A marked elevation of neuropeptide Y immunoreactivity in the mossy fiber, and Y2-receptor up-regulation in the dentate gyrus were observed in the hippocampus of Noda epileptic rat, which coincided with the previous results of the other epileptic models. In contrast, Y1-receptor down-regulation was not found after a spontaneous seizure of Noda epileptic rat while this occurs in kindling and after kainic acid-induced seizures. [125I][Leu31, Pro34]peptide YY/BIBP 3226-insensitive (Y5 receptor) binding sites in CA1 stratum radiatum were significantly decreased following a spontaneous seizure of Noda epileptic rat. The present results suggest that a spontaneous seizure of Noda epileptic rat induces significant changes in neuropeptide Y-mediated transmission in the hippocampus via Y2 and Y5 receptors, but not Y1 receptors. Therefore, specific subset of neuropeptide Y receptor subtypes might be involved in the epileptogenesis of Noda epileptic rat.

Reduction in levels of amphiphysin 1 mRNA in the hippocampus of aged rats subjected to repeated variable stress.

Various neurobiological studies of aging indicate that elevated levels of circulating glucocorticoids lead to hippocampal vulnerability to stress, though little is known about the molecular mechanism underlying stress vulnerability in the elderly. We have compared the gene expression profiles in the hippocampus of aged (20 months) and adult (3 months) rats in response to repeated variable stress (RVS) for 4 days, using a cDNA array technique and real-time quantitative PCR, to identify putative genes involved in the mechanism of stress vulnerability in the elderly. We found a significant decrease in the levels of amphiphysin 1 mRNA in aged rats subjected to RVS compared with treated and untreated adult rats or to untreated aged rats. Similarly, we found a significant decrease in hippocampal levels of amphiphysin 1 mRNA in aged rats subjected to RVS for 8 days, but not in those subjected to a single VS. These findings suggest that the decrease in the hippocampal levels of amphiphysin 1 mRNA in response to repeated stress may be involved in the stress vulnerability in the elderly, and may lead to the disturbance of learning and memory under stressful conditions in the elderly.

Chronic lithium treatment increases the expression of brain-derived neurotrophic factor in the rat brain.

RATIONALE: Lithium is the most widely prescribed mood stabilizer, but the precise mechanism of lithium is unresolved. OBJECTIVE: We examine the effects of the administration of therapeutically relevant concentrations of lithium on the expression of brain-derived neurotrophic factor (BDNF) and its receptor, Trk B, as well as glia-derived neurotrophic factor (GDNF) and its receptors, RET and GDNFR-alpha, in the rat brain. In addition, we also examined the effect of another well-prescribed mood stabilizer, valproate, on the expression of BDNF and GDNF. METHODS: Rats were kept on a 0.2% lithium carbonate-containing diet for 1, 7, 14, or 28 days or treated with valproate (400 mg/kg per day i.p.) for 1 or 14 days. After the brains were rapidly removed, the levels of BDNF, GDNF, and their receptors were measured by ELISA or western blot analysis. RESULTS: Chronic lithium treatment for 14 and 28 days significantly increased the expression of BDNF in the hippocampus and temporal cortex. In addition, chronic lithium treatment for 14 days significantly increased the expression of BDNF in the frontal cortex. In contrast, acute or chronic dietary lithium treatment did not alter GDNF expression in these brain regions. In addition, acute or chronic lithium treatments did not change the levels of Trk B, RET, or GDNFR-alpha immunoreactivity. As well as lithium, repeated administration of valproate also increased the expression of BDNF in the frontal cortex and hippocampus. CONCLUSIONS: Our results suggest that the chronic administration of mood stabilizers may produce a neurotrophic effect mediated by the upregulation of BDNF in the rat brain.

Correlation of regional cerebral blood flow with performance on neuropsychological tests in schizophrenic patients.

Regional cerebral blood flow (rCBF) was determined by the 133Xe inhalation technique (Headtome II: ring detection SPECT) in 53 DSM-III schizophrenic patients. The rCBF values were corrected by using end-tidal carbon dioxide concentration values (PECO2). After rCBF measurement, neuropsychological tests--Word Fluency Test, Maze Test and Wisconsin Card Sorting Test--were performed. There were significant correlations between frontal rCBF and scores on each neuropsychological test. In particular, a moderate correlations between the frontal rCBF and the performance on the Wisconsin Card Sorting Test was noted. It seems likely that decrease of rCBF in prefrontal regions at rest reflects a disturbance of frontal lobe function in schizophrenic patients.

Elevated neuropeptide Y and corticotropin-releasing factor in the brain of a novel epileptic mutant rat: Noda epileptic rat.

Noda epileptic rat (NER) is a new epileptic rat strain, which was developed by inbreeding rats with spontaneous tonic-clonic seizures in a stock of Crj:Wistar. In the present study, possible changes of two neuropeptides, neuropeptide Y (NPY) and corticotropin-releasing factor (CRF), in the brains of NER were investigated. Increased contents of immunoreactive (IR) NPY were found in the striatum and amygdala of 8-week NERs with partial seizure, while these changes extended to the limbic region including hippocampus in 16-week NERs with fully developed generalized tonic-clonic seizure. IR-CRF were elevated only in the entorhinal and pyriform cortex of both 8-week and 16-week NERs. Generalized tonic-clonic seizure in NERs induced a transient increase of NPY mRNA in the granular layer of dentate gyrus. These results suggest that NPY metabolism in the limbic brain contributes to the seizure susceptibility in this model of epilepsy.

Influence of aging on the contractile response to endothelin of rat thoracic aorta.

Age-related changes in the contractile response to endothelin-1 and ACh were assessed in thoracic aortas isolated from 2-, 6- and 24-month-old male Fischer 344 rats. In aortic strips with an intact endothelium, the maximal contractile response to endothelin-1 decreased with development to maturity. Removal of the endothelium did not affect the contractile response to endothelin-1. Endothelin-1 did not elicit a relaxant response in phenylephrine-precontracted strips. The ACh-induced relaxation decreased in senescent rats. These results indicate that the contractile response of aortic smooth muscle to endothelin-1 decreases with age, and that the endothelial vasorelaxant factors do not contribute to this age-induced modulation.

Influence of stress and antidepressant treatment on 5-HT-stimulated phosphoinositide hydrolysis in rat brain.

The aim was to elucidate the role of 5-hydroxytryptamine (5-HT)-stimulated phosphoinositide (PI) metabolism in stress situations and in the behavioral improvement produced by chronic antidepressant treatment. Rat cerebral cortex slices were used for the purpose. Forced swimming for 15 min and longer induced changes in behavioral activities of rats associated with a significant reduction of 5-HT-stimulated PI metabolism, without any changes in density and affinity of 5-HT2 receptors. This suggests that modulation of the receptor coupling process but not of the 5-HT2 receptor binding characteristics may be responsible for the significant reduction of 5-HT-stimulated PI metabolism in stress situations. Chronic antidepressant treatment tended to reduce 5-HT-stimulated PI metabolism. This treatment improved significantly the behavioural activities during forces swimming, and prevented the forced swimming-induced reduction of 5-HT-stimulated PI metabolism. It is postulated that chronic antidepressant treatment may improve behavioral activities in relation to PI metabolism in stress situations.

Enhancement of 5-hydroxytryptamine-stimulated phosphoinositide hydrolysis in the rat cerebral cortex by repeated immobilization stress.

The present study was undertaken to investigate the influence of repeated immobilization stress on phosphoinositide hydrolysis induced by 5-hydroxytryptamine (5-HT) and noradrenaline in the rat cerebral cortex. Three groups of rats subjected to stress intervention were immobilized for 2 h per day for 3, 7, and 14 days. The stress intervention of any duration did not alter noradrenaline-stimulated phosphoinositide hydrolysis. The 3- and 7-day repeated immobilization enhanced 5-HT-stimulated phosphoinositide hydrolysis, whereas the characteristics of 5-HT2 receptor binding did not change. Chronic treatment with imipramine partially, but significantly, suppressed the increase in 5-HT-stimulated phosphoinositide hydrolysis, induced by the 3-day repeated immobilization. These findings imply that modulation of 5-HT-stimulated phosphoinositide hydrolysis occurs in stressful situations and that the therapeutic effects of tricyclic antidepressant drugs might be related to the modulation of phosphoinositide hydrolysis mediated by 5-HT receptors.

Effect of beta-estradiol on voltage-gated Ca(2+) channels in rat hippocampal neurons: a comparison with dehydroepiandrosterone.

We investigated the effects of beta-estradiol, dehydroepiandrosterone and dehydroepiandrosterone sulfate on intracellular calcium concentration ([Ca(2+)](i)) increases induced by gamma-aminobutyric acid (GABA), high K(+) and N-methyl-D-aspartate acid (NMDA) in cultured hippocampal neurons. Acute treatment with beta-estradiol, dehydroepiandrosterone and dehydroepiandrosterone sulfate inhibited the GABA-induced [Ca(2+)](i) increases to the similar extent. Tamoxifen, an estrogen receptor antagonist, did not block the inhibitory effects of beta-estradiol. On the other hand, GABA type A (GABA(A)) receptor antagonists, picrotoxin and bicuculline, blocked the GABA-induced [Ca(2+)](i) increases. Previously, we demonstrated that GABA- and high K(+)-induced [Ca(2+)](i) increases were commonly mediated by voltage-gated calcium channels (VGCCs). Therefore, we examined the effects of these steroids on the high K(+)-induced [Ca(2+)](i) increases. The inhibitory effect of beta-estradiol on the high K(+)-induced [Ca(2+)](i) increases was much greater than that of dehydroepiandrosterone and dehydroepiandrosterone sulfate. beta-Estradiol inhibited the NMDA-induced [Ca(2+)](i) increases with an IC(50) of 51.8 microM and NMDA responses were reduced to half in the presence of 10 micro M nifedipine, indicating that the NMDA-induced [Ca(2+)](i) increases also involved VGCCs. Further, we examined the inhibitory effect of beta-estradiol on the high K(+)-induced [Ca(2+)](i) increases in the presence of a N-type VGCCs antagonist, 1 microM omega-conotoxin, or a L-type VGCCs antagonist, 10 microM nifedipine. The IC(50) value of beta-estradiol alone (45.5 microM) was similar to that of omega-conotoxin (33.1 microM), while the value combined with nifedipine was reduced to 2.2 microM. beta-Estradiol also abolished the positive modulatory effect of L-type VGCCs agonist, 1,4-dihydro-2,6-dimethyl-5-nitro-4-[2-(trifluoromethyl)phenyl]pyridine-3-carboxylic acid methyl ester (Bay K 8644). Our results showed that the inhibitory mechanism of beta-estradiol is different from that of dehydroepiandrosterone and dehydroepiandrosterone sulfate and beta-estradiol may act primarily at L-type VGCCs.

Modulation of serotonin2A receptor function in rats after repeated treatment with dexamethasone and L-type calcium channel antagonist nimodipine.

1. It has been conceivable that the hypothalamic-pituitary-adrenal (HPA) axis hyperactivity plays an important role in the pathophysiology of depression. In the present study, we have investigated the effect of repeated treatment with dexamethasone on serotonin (5-HT) 1A, 5-HT2A and alpha1-adrenergic receptors in the rat frontal cortex. Moreover, several studies have suggested the effectiveness of L-type calcium channel antagonist nimodipine for the treatment of depression. We also investigated the effect of repeated treatment with nimodipine on 5-HT2A receptor in rats with repeated dexamethasone treatment. 2. Repeated treatment with dexamethasone (1 mg/kg/day for 14 days) increased the density of 5-HT2A receptor, but not 5-HT1A and alpha1-adrenergic receptors in the rat frontal cortex. 3. The density of 5-HT2A receptor in the rat frontal cortex was significantly increased 1 day after repeated treatment with dexamethasone, but was not increased 7 or 14 days after repeated treatment. Wet dog shakes (WDS) induced by (+/-)-1-(4-iodo-2,5-dimethoxyphenyl)-2-aminopropane hydrochloride (DOI), a 5-HT2A receptor agonist, in rats were significantly enhanced 1, 7 and 14 days after repeated treatment with dexamethasone, although the frequency of WDS gradually decreased after repeated treatment. 4. Repeated treatment with nimodipine (5 mg/kg/day for 14 days) attenuated DOI-induced WDS enhanced by repeated treatment with dexamethasone (1 mg/kg/day for 14 days), however, it did not change the density of 5-HT2A receptor. Repeated treatment with dexamethasone decreased locomotor activity and body weight, but repeated treatment with nimodipine did not recover these parameters. 5. The results of the present study suggest that repeated treatment with dexamethasone may selectively increase the 5-HT2A receptor in the rat frontal cortex and affect 5-HT2A receptor-mediated signal transduction. In addition, the intracellular calcium homeostasis by blocking calcium influx through L-type calcium channel may play an important role in the regulation of the 5-HT2A receptor function by dexamethasone.

Influence of the acute stress on agonist-stimulated phosphoinositide hydrolysis in the rat cerebral cortex.

1. The present study was carried out in order to elucidate the influence of the acute stress on alpha 1-adrenergic, serotonin-2 (5-HT2) and muscarinic cholinergic (M-Ach) receptors-mediated phosphoinositide (PI) hydrolysis in rat cerebral cortex slices. 2. In rat cerebral cortex slices, noradrenaline (NA), serotonin (5-HT) and carbachol stimulated [3H]inositol-monophosphate (IP1) accumulation in a concentration-dependent manner. 3. The forced swimming test (FST) for 15 min induced a significant reduction of 5-HT-stimulated [3H]IP1 accumulation, but this stress situation did not produce a significant alteration of NA- and carbachol-stimulated [3H]IP1 accumulation. 4. The FST for 15 min did not affect the density and affinity of alpha 1-adrenergic, 5-HT2 and M-Ach receptors. 5. In a mild acute stress situation, the intracellular signal transduction mediated by 5-HT was promptly inhibited as compared to the signal transduction mediated by NA or carbachol. This inhibition may be induced by an acute uncoupling of 5-HT2 receptor-mediated intracellular signal transduction.

Modulation by aging of the coronary vascular response to endothelin-1 in the rat isolated perfused heart.

Changes with age in the coronary vascular response to endothelin-1 were investigated in perfused hearts isolated from 2-, 6- and 24-month-old (mo) male Fisher-344 rats. Endothelin-1 injected as a single bolus (0.3, 3 and 30 nmol) into the coronary artery supply caused dose-dependent vasoconstriction in all three age groups. While there was no age-related change in the vasoconstriction induced by the lower doses (0.3 and 3 nmol), the higher dose (30 nmol) elicited a more pronounced vasoconstriction in 6- and 24-mo rats than that in 2-mo rats. NG-nitro-L-arginine (L-NNA), an inhibitor of nitric oxide formation, markedly enhanced the vasoconstriction induced by 30 nmol endothelin-1 in 2- and 6-mo rats but only slightly and non-significantly enhanced that vasoconstriction in 24-mo rats. Haemoglobin, which inhibits activation of guanylate cyclase by nitric oxide, enhanced the endothelin-1-induced vasoconstriction in 2-mo rats, but not in 6- and 24-mo rats. The acetylcholine-induced coronary vasodilation was more pronounced in 2- and 6-mo rats than in 24-mo rats and was attenuated by L-NNA in 2- and 6-mo rats. The coronary vasodilation induced by nitroprusside (0.1 mmol), a pharmacological precursor of nitric oxide, did not change with age. Endothelin-1 (30 nmol) markedly increased the release of 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha) in all three age groups. The prostaglandin synthesis inhibitor indomethacin enhanced the endothelin-1-induced vasoconstriction in 2- and 6-mo rats to a similar extent.(ABSTRACT TRUNCATED AT 250 WORDS)

Chronic dexamethasone administration decreases noradrenaline-stimulated, but not serotonin-stimulated, phosphoinositide metabolism in the rat brain.

The present study was undertaken to investigate the effects of chronic administration of dexamethasone on the noradrenaline- and serotonin-stimulated (5-HT-stimulated) phosphoinositide metabolism in hippocampus and frontal cortex of the rat brain. For determination of phosphoinositide metabolism, slices from selected regions of the rat brain (hippocampus or frontal cortex) were loaded with myo- [3H] inositol and stimulated with the agonists (noradrenaline or 5-HT) in the presence of LiCl (7.5 mM). Administration of dexamethasone (1 mg/kg/day) every 2nd day for 14 days markedly reduced the noradrenaline-stimulated phosphoinositide metabolism in the rat hippocampus (IP1: 60% of the control value). In the rat frontal cortex, the noradrenaline-stimulated phosphoinositide metabolism was less depressed by the chronic administration of dexamethasone (IP1: 84% of the control value). However, the chronic administration of dexamethasone did not affect the 5-HT-stimulated phosphoinositide metabolism in the rat brain. The binding characteristics of alpha 1 -adrenoceptors and 5-HT2A receptors were unaffected by the chronic treatment with dexamethasone. These results indicate that chronic administration of dexamethasone induces regional and neurotransmitter-specific changes of phosphoinositide metabolism in rat brain. The results suggest that the reduction of noradrenaline-stimulated phosphoinositide metabolism is due to modification of the intracellular signal transduction system.