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N Barden

Publications and source records attributed to N Barden.

At least 19 recordsLinked to original sources
PubMed1992

Chronic estradiol treatment increases anterior pituitary but not striatal D2 dopamine receptor mRNA levels in rats.

The effect of chronic 17 beta-estradiol treatment (10 micrograms, twice each day, for 2 weeks) of ovariectomized rats on D2 dopamine (DA) receptor mRNA levels was investigated in striatum and anterior pituitary gland tissues. We used 32P-labeled probes specific for D2 receptor and beta-actin mRNAs in Northern blot analysis. The ratio of D2 DA receptor mRNA/beta-actin mRNA level was significantly increased in the anterior pituitary of estradiol-treated rats compared to vehicle-treated animals. The D2 DA receptor mRNA/beta-actin mRNA ratio in the striatum was not affected by estradiol treatment. However, the medial portion of the striatum showed a significantly lower ratio compared to the lateral portion of the striatum in both vehicle- and estradiol-treated rats. Thus, the estradiol effect on anterior pituitary D2 receptors may implicate transcriptional regulation, whereas our results do not support this hypothesis for the estradiol action on striatal D2 receptors.

Actins↗
PubMed1992

Impaired type II glucocorticoid-receptor function in mice bearing antisense RNA transgene.

Glucocorticoids, in conjunction with their cognate receptors, exert negative-feedback effects on the hypothalamus-pituitary-adrenal axis, suppressing adrenal steroid secretions. Two types of corticosteroid receptor, distinguishable by their ability to bind corticosterone, have been identified as classical mineralocorticoid (type I) and glucocorticoid (type II) receptors by cloning their complementary DNAs. The type I receptor controls the basal circadian rhythm of corticosteroid secretion. Both receptor types are involved in negative feedback, but the type II receptor may be more important for terminating the stress response as it is the only one to be increased in animals rendered more sensitive to corticosteroid negative-feedback effects. Here we create a transgenic mouse with impaired corticosteroid-receptor function by partially knocking out gene expression with type II glucocorticoid receptor antisense RNA. We use this animal to study the glucocorticoid feedback effect on the hypothalamus-pituitary-adrenal axis.

Adrenal Glands↗
PubMed1992

Antidepressant drug action in a transgenic mouse model of the endocrine changes seen in depression.

We have created transgenic mouse lines with impaired glucocorticoid receptor function by expression of a type II glucocorticoid receptor antisense RNA in brain tissues. These animals have endocrinological characteristics similar to those seen in depression, including a hyperactive hypothalamic-pituitary-adrenal axis as indicated by elevated plasma corticosterone and adrenocorticotropin hormone levels. Treatment of transgenic animals with the tricyclic antidepressant desipramine increased hypothalamic glucocorticoid receptor mRNA concentration and dexamethasone-binding activity while decreasing plasma adrenocorticotropin hormone concentration and corticosterone levels. These results support the hypothesis that antidepressants exert action on the hypothalamic-pituitary-adrenal axis through modulation of glucocorticoid receptor gene expression.

Actins↗
PubMed1992

Increased glucocorticoid receptor gene promoter activity after antidepressant treatment.

We have tested the hypothesis that antidepressants affect the expression of the glucocorticoid receptor gene, by looking at glucocorticoid receptor gene promoter activity, glucocorticoid receptor mRNA levels, and glucocorticoid-binding activity after treatment of different cell lines with desipramine. Treatment of LTK- cells or Neuro 2A cells with desipramine produced a 50-200% increase in chloramphenicol acetyltransferase activity transcribed from a 2.7-kilobase glucocorticoid receptor gene promoter region. In cell lines derived from both neuronal and non-neuronal sources, glucocorticoid receptor mRNA concentration doubled after desipramine treatment, and this was associated with a 2-fold higher functional glucocorticoid binding capacity and increased glucocorticoid sensitivity, as measured with the reporter plasmid pMMTVCAT. Antidepressant-induced increases in glucocorticoid receptor gene promoter activity, glucocorticoid receptor mRNA levels, and functional glucocorticoid binding activity suggest a novel mechanism of action for these drugs on the hypothalamic-pituitary-adrenal axis.

Animals↗
PubMed1991

Biphasic regulation of proopiomelanocortin messenger RNA concentrations by corticotropin-releasing factor in primary cultures of rat hypothalamic neurons.

Primary cultures of rat hypothalamic neurons in which a 1.1-kb proopiomelanocortin (POMC) mRNA can be detected, were incubated with corticotropin-releasing factor (CRF) for periods of up to 84 h. A cyclic modulation of POMC mRNA concentrations by CRF was noted. A rapid acute inhibition of POMC mRNA levels after 1 h of exposure was followed by a transient stimulation and then by a more prolonged inhibition which reached a nadir after 48 h.

Animals↗
PubMed1991

Monoaminergic regulation of proopiomelanocortin messenger RNA concentrations in primary cell cultures of rat hypothalamus.

The effect of monoaminergic neurotransmitters on a 1.1-kb proopiomelanocortin messenger RNA (POMC mRNA) detected in rat hypothalamic cells maintained in culture has been evaluated. Serotonin caused a 15% increase in POMC mRNA levels, an effect which was blocked by the 5-HT2 receptor antagonist ketanserin. Dopamine markedly decreased POMC mRNA levels in a dose related manner. Haloperidol and the selective D2 antagonist (+)-butaclamol prevented the inhibitory effects of both dopamine and the selective D2 agonist, 2-bromo-alpha-ergocryptine. The selective dopamine D1 receptor agonist, SKF 38393, as well as norepinephrine and acetylcholine did not affect POMC mRNA levels. It is concluded that serotonin exerts a positive control and dopamine a negative control on POMC mRNA concentrations in primary cultures of rat hypothalamic neurons. The negative effect of dopamine appears to be exerted via D2 receptor-mediated mechanism.

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗
PubMed1991

Regulation of proopiomelanocortin messenger RNA concentrations by opioid peptides in primary cell cultures of rat hypothalamus.

The effects of opioid peptides on a 1.1-kb long proopiomelanocortin messenger RNA (POMC mRNA) have been investigated in rat hypothalamic cells maintained in culture. Most opioid peptides exerted an inhibitory control on POMC mRNA steady-state concentrations. beta-Endorphin caused a 65% maximal inhibitory effect (IC50 = 6.1 x 10(-9) M) while slightly less inhibition was caused by Met- and Leu-enkephalin, dynorphin A and DADLE ([D-Ala2,D-Leu5] enkephalin). The effects of beta-endorphin and of Met-enkephalin were completely reversed by the delta opioid antagonist ICI 174,864 while the kappa-receptor specific antagonist binaltorphimine or the sigma-receptor specific antagonist DTG (1,3-di(2-tolyl) guanidine) respectively blocked the inhibitory actions of dynorphin A and of DADLE. The mu-receptor specific agonist DAGO ([D-Ala2,N-Me-Phe4,Gly5-OL]enkephalin) did not affect POMC mRNA levels. The failure of the dopaminergic D2 antagonist haloperidol to modify the inhibitory effects of opioid peptides argues for a direct inhibitory opioid peptide modulation of hypothalamic POMC mRNA levels mediated by the delta-, kappa- and sigma- (but not mu-) receptors in vivo.

Animals↗
PubMed1991

Antidepressant and other centrally acting drugs regulate glucocorticoid receptor messenger RNA levels in rat brain.

The effect of imipramine, desipramine, ketanserin and lithium on Type II glucocorticoid receptor (GR) mRNA levels was studied in rat brain regions involved in the control of the hypothalamo-pituitary-adrenal (HPA) axis, the dysregulation of which has been implicated in the pathophysiology of major depression. Northern blot analysis of Type II GR mRNA showed that treatment of male rats with either desipramine or imipramine increased hypothalamic and hippocampal GR mRNA levels. Upregulation of GR mRNA following administration of imipramine was found in brain regions of female rats, while desipramine had no effect. Ketanserin increased levels of GR mRNA in hippocampus of male, but not female, rats. Lithium also was able to induce important increases rat brain GR mRNA; this effect was particularly marked in females. We conclude that desipramine, imipramine, ketanserin and lithium can modulate GR mRNA in regions of rat brain involved in the control of the HPA axis and may have a common mechanism of action at the level of the GR gene. Sexual dimorphism for drug regulation of brain GR mRNA content was shown and may be related to sex differences in the prevalence of certain affective disorders.

Amygdala↗
PubMed1991

Decreased glucocorticoid receptor activity following glucocorticoid receptor antisense RNA gene fragment transfection.

Depression is often characterized by increased cortisol secretion caused by hyperactivity of the hypothalamic-pituitary-adrenal axis and by nonsuppression of cortisol secretion following dexamethasone administration. This hyperactivity of the hypothalamic-pituitary-adrenal axis could result from a reduced glucocorticoid receptor (GR) activity in neurons involved in its control. To investigate the effect of reduced neuronal GR levels, we have blocked cellular GR mRNA processing and/or translation by introduction of a complementary GR antisense RNA strand. Two cell lines were transfected with a reporter plasmid carrying the chloramphenicol acetyltransferase (CAT) gene under control of the mouse mammary tumor virus long terminal repeat (a glucocorticoid-inducible promoter). This gene construction permitted assay of the sensitivity of the cells to glucocorticoid hormones. Cells were also cotransfected with a plasmid containing 1,815 bp of GR cDNA inserted in the reverse orientation downstream from either a neurofilament gene promoter element or the Rous sarcoma virus promoter element. Northern (RNA) blot analysis demonstrated formation of GR antisense RNA strands. Measurement of the sensitivity of CAT activity to exogeneous dexamethasone showed that although dexamethasone increased CAT activity by as much as 13-fold in control incubations, expression of GR antisense RNA caused a 2- to 4-fold decrease in the CAT response to dexamethasone. Stable transfectants bearing the GR antisense gene fragment construction demonstrated a 50 to 70% decrease of functional GR levels compared with normal cells, as evidenced by a ligand-binding assay with the type II glucocorticoid receptor-specific ligand [3H]RU 28362. These results validate the use of antisense RNA to GR to decrease cellular response to glucocorticoids.

Animals↗
PubMed1991

Hormonal regulation of type II glucocorticoid receptor messenger ribonucleic acid in rat brain.

Differences in the regulation of type II glucocorticoid receptor (GR) mRNA levels in female rat brain regions involved in the control of the hypothalamic-pituitary-adrenal axis were studied by Northern blot analysis after chronic administration of corticosterone or dexamethasone to adrenalectomized (ADX), ovariectomized (OVX), and ADX/OVX animals. The effect of chronic estradiol or progesterone treatment of intact animals was also studied. Our results show that type II GR mRNA levels of ADX animals were significantly increased above control values in amygdala (140%) and hippocampus (196%), but not in hypothalamus. These increased transcript levels were down-regulated by corticosterone or dexamethasone, with the exception of those in the amygdala, where corticosterone had no effect. Ovariectomy significantly increased hypothalamic GR mRNA content (174%) over control values, and this increase was sensitive to dexamethasone. The combined effect of adrenalectomy/ovariectomy on GR mRNA levels was greater than that of adrenalectomy only in amygdala. Corticosterone increased amygdala transcript levels in OVX and ADX/OVX animals. Estradiol administration to intact animals raised the GR mRNA content of amygdala, while progesterone treatment had no effect on any of the brain regions studied. We conclude that there exists heterogeneity with respect to type II GR mRNA regulation by corticosterone and dexamethasone in brain regions of ADX female rats, and that certain limbic structures show greater sensitivity to these hormonal manipulations, suggesting a more prominent role in the regulation of the hypothalamic-pituitary-adrenal axis. Our results also suggest that circulating estrogens can influence the sensitivity of brain structures (i.e. hypothalamus and amygdala) to glucocorticoids by altering GR mRNA levels. These regions may represent integration sites at which gonadal steroids are able to alter stress hormone secretion.

Adrenalectomy↗
PubMed1990

Differential regulation by dexamethasone of glucocorticoid receptor messenger RNA concentrations in neuronal cultures derived from fetal rat hypothalamus and cerebral cortex.

1. Differential regulation, by dexamethasone, of glucocorticoid receptor gene expression was studied in three different neuronal cultures derived from hypothalamus amygdala, and cerebral cortex. 2. Cellular glucocorticoid receptor (GR) mRNA concentration was measured by hybridization using a 32P-labeled RNA probe complementary to a 2.2-kb fragment of the glucocorticoid receptor mRNA. Changes in the amount of GR mRNA were evaluated in relation to the content of beta-actin mRNA. 3. In cells derived from either hypothalamus or cerebral cortex, we observed a complex pattern of GR mRNA concentrations which were characterized by cyclic variations of GR mRNA content during continuous treatment with dexamethasone for up to 72 hr. 4. In contrast to cells derived from the hypothalamus where a persistent 30-40% reduction in GR mRNA levels was seen for up to a least 72 hr, we observed, in cells derived from the cerebral cortex, a sustained increased (1.4-fold) of the GR mRNA at this same time interval.

Animals↗
PubMed1989

Antidepressants regulate glucocorticoid receptor messenger RNA concentrations in primary neuronal cultures.

Increased cortisol secretion, caused by hyperactivity of the brain-pituitary-adrenal axis, and non-suppression of cortisol secretion following dexamethasone administration are two characteristics frequently associated with major depression or the depressed phase of bipolar illness. Antidepressants, irrespective of their selective inhibitory actions on the re-uptake of serotonin or of norepinephrine, modify glucocorticoid receptor messenger RNA concentrations in primary cultures of rat hypothalamic or amygdaloid neurons in a biphasic manner, with predominant stimulatory effects. This suggests a mechanism whereby antidepressants, by restoring the sensitivity of the limbic-hypothalamic system to glucocorticoid feedback inhibition, reverse the hyperactivity of the brain-pituitary-adrenal axis.

Amygdala↗
PubMed1989

Influence of the central nucleus of the amygdala on the content of corticotropin-releasing factor in the median eminence.

The central nucleus of the amygdala possesses numerous neurons containing corticotropin-releasing factor (CRF). This study demonstrates a striking decrease of the CRF-like immunoreactivity in the median eminence at both 1 and 2 weeks after bilateral lesions of the amygdaloid central nucleus. Lesion of the amygdaloid central nucleus did not alter the neurophysin-like immunoreactivity in the internal zone of the median eminence, indicating the integrity of the efferent neurophysin-containing fibers of the supraoptic and paraventricular hypothalamic nuclei. However, there was a concomitant decrease of neurophysin and CRF-like immunoreactivity in the external zone of the median eminence. These results substantiate the hypothesis that the amygdaloid central nucleus can influence the content of CRF-like material in the median eminence via a multisynaptic pathway involving the synthesis of CRF at the level of the paraventricular nucleus of the hypothalamus. The exact mechanism by which lesion of the amygdaloid central nucleus influences the CRF content in the median eminence remains to be determined.

Amygdala↗
PubMed1989

Effect of corticotropin-releasing factor on the release and synthesis of prolactin.

Corticotropin-releasing factor (CRF) has been characterized on the basis of its intrinsic activity to release corticotropin from cultured rat anterior pituitary cells. Injected in intact rats, CRF increases adrenocorticotropic hormone (ACTH) release. Endogenous CRF-like immunoreactivity was detected in the cytoplasm and nucleus of corticotrophs. Using an antirat CRF serum, a similar location of CRF-like immunoreactivity was observed in lactotrophs: cytoplasmic matrix, secretory granules, nucleus and, to a lesser degree, the plasma membrane level were stained. One injection of CRF increased the plasma ACTH concentration 4-fold after 15 min, while plasma prolactin (PRL) increased 2.7-fold 5 min after injection. In vitro, incubation of female pituitary cells with rat CRF (10(-10)-10(-8) M) had no significant effect on PRL secretion. In contrast, after 4 days of in vitro pretreatment with 17 beta-estradiol (10(-9) M), rat CRF stimulated PRL secretion by 42%. In situ hybridization of whole pituitary slices showed that rat CRF injection significantly increased the labeling of corticotrophs using an ACTH-cDNA probe, but had no significant effect on the labeling of lactotrophs using a PRL riboprobe. These results indicate that CRF is a factor which can modulate PRL release but not the synthesis of PRL.

Adrenocorticotropic Hormone↗
PubMed1988

Glucocorticoid receptor gene expression in rat pituitary gland intermediate lobe following ovariectomy.

Using hybridization techniques and Northern blots we have identified a approximately 6.5 kb glucocorticoid receptor mRNA species in rat pituitary intermediate lobe. Glucocorticoid receptor mRNA concentrations, which are barely detectable or undetectable in normal animals, were greatly increased following ovariectomy. This ovariectomy-induced increase in glucocorticoid receptor mRNA content of the intermediate lobe, which was confirmed by in situ hybridization experiments, could be reversed by 17 beta-estradiol administration.

Animals↗
PubMed1988

Effect of luteinizing hormone releasing hormone (LHRH) and [D-Trp6, des-Gly-NH2(10)]LHRH ethylamide on alpha-subunit and LH beta messenger ribonucleic acid levels in rat anterior pituitary cells in culture.

The effect of incubation with LHRH and its agonist [D-Trp6, des-Gly-NH2(10)]LHRH ethylamide has been measured on the concentrations of mRNAs for the common alpha-subunit of glycoprotein hormones and beta-LH in rat anterior pituitary cells in primary culture. After incubation, total RNA was analyzed by Northern blot or dot blot hybridization with alpha- and LH beta 32P-labeled cRNA probes and mRNA levels were quantified by autoradiography. Short-term treatment (4-6 h) of pituitary cells with 100 nM LHRH led to a marked stimulation of LH release but no effect was observed on alpha-subunit or LH beta mRNA levels. Longer (24-72 h) incubation periods with LHRH led to complete desensitization of the LH response to the neurohormone and induced 2- to 3-fold increases in alpha-mRNA cell content while LH beta mRNA levels remained unchanged. Maximal induction of alpha mRNA accumulation was observed with an LHRH concentration as low as 0.1 nM. Incubation with the LHRH agonist [D-Trp6, des-Gly-NH2(10)]LHRH ethylamide for 24-72 h also increased alpha mRNA but did not modify LH-beta mRNA levels. It is concluded that long-term exposure of anterior pituitary cells to LHRH or to an LHRH agonist positively regulates alpha-subunit gene expression in the absence of change in LH beta mRNA levels. This observation can provide an explanation for the high plasma levels of free alpha-subunits found in patients treated chronically with LHRH agonists.

Animals↗
PubMed1988

Glucocorticoid regulation of proopiomelanocortin messenger ribonucleic acid content of rat hypothalamus.

We have verified the possibility that the POMC gene of the rat hypothalamus might be subject to regulation by glucocorticoids. Adrenalectomy increased the concentration of POMC mRNA in anterior pituitary and in hypothalamus, but not in the neurointermediate lobe of the pituitary gland. Dexamethasone and, to a slightly lesser extent, corticosterone treatments reversed the adrenalectomy-induced increase in POMC mRNA concentrations in both anterior pituitary and hypothalamus. Dexamethasone caused a slight decrease of POMC mRNA levels in the neurointermediate lobe of the pituitary gland, while corticosterone had no effect. These results indicate that the POMC gene of the rat brain hypothalamus is also under negative control by glucocorticoids.

Adrenalectomy↗