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  • 1
    ISSN: 1573-6830
    Keywords: (Na + K)-ATPase ; deoxycorticosterone ; salt intake ; mineralocorticoids ; in situ hybridization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary 1. We have usedin situ hybridization techniques to determine the mRNA for (Na + K)ATPase in 20 brain regions from control rats and rats treated with high doses of deoxycorticosterone (DOC). 2. DOC-treated rats developed a salt appetite following the second hormone administration on alternate days and were used after the fourth DOC administration. 3. DOC treatment did not change the number of silver grains/cell deposited in cells from Ca1, CA2, CA3, and CA4 hippocampal subfields, dentate gyrus, cerebral cortex, medial preoptic area (POA), substantia nigra, and periventricular gray matter. 4. Nonsignificant reductions were detected in lateral POA, medial and lateral septum, caudate-putamen, and three amygdaloid nuclei (cortical, basolateral, and central) from DOC-treated rats. 5. Significant reductions were obtained, after DOC administration, in arcuate and ventromedial hypothalamic nuclei and medial and lateral amygdala. 6. The results suggested that regulation of theβ-subunit mRNA of (Na + K)-ATPase may be related to the central actions of mineralocorticoids in the control of salt intake.
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  • 2
    ISSN: 1573-6830
    Keywords: adrenal steroids ; plasticity ; hippocampal neurons ; stress ; neuron loss ; glutamate ; serotonin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
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  • 3
    ISSN: 0730-2312
    Keywords: antisensense oligonucleotides ; pertussis toxin ; splenocytes ; Nb2 cells ; Giα ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: In a previous report we shwed that glucocorticoed inhibition of cytosolic PLC activity correlated with a reduction in cytosolic Giα levels, suggesting that there may be a functional relationship between cytosolic PLC and cytosolic Giα. In order to establish the nature of the coupliing between cytosolic Giα and cytosolic PLC we examined the effects of Protein activators, and inhibitors on cytosolic PLC activity from rat spenocytes and the rat lymphoma cell line Nb 2, with [3H] PI and [3H]PIP2 as substrates. (1) Neither GTP nor its nonhydrolyzable analogue, GTPγS, at 100 μm had any effect on the calcium stimulated as well as the basal PLC activity. (2) Howevr, affinity purified antibodies to Giα1 and Giα2 inhibited soluble PLC activity, by 85% and 55%, respectively, with PI as substrate; with PIP2 as substrate, soluble PLC activity was inhibited 50-70% by antibodies to Gi1, whereas antibodies to Gi2 had little effect. (3)Administration of Giα1 antisense oligonucleotides to splenocytes for 48 h produced 25-40% decrease in cytosolic Giα1 levels compared to control. The soluble PLC activity with both PI and PIP2 as substrates was also reduced by 25-50% compared to control conditions. This suggest that cytosolic Giα is associated with the activation of splenocyte soluble PLC. (4) Pertussis toxin administered in vivo sugnificantly reduced cytosolic Giα immunoreactivity and soluble PLC activiry when PI was used as substrate, providing additional evidence that cytosolic Giα is associated with the activation of splencyte soluble PLC. (5) Another agent that has beeen used extensively to define G-protein coupled processes is NaF/AlCl3. NaF(4mM; with or without AlCl3 inhibited soluble PLC activity with PIP2 as substrate, in contrast ot the stimulatory effect that has been reported in the activation of membrane PLC. 6) because NaF can act as a protein phosphatase inhibitor, we also tested the effects of trifluoperzine (50 μm, TFP), an inhibitor of protein phosphatase 2B; TFP (50 μm) signigicantly inhibited soluble PLC activity PI was used as substrate. These results suggest a direct involvement of cytosolic Giα in the activation of soluble PLC form splenocytes. Other questions pertaining to the functional significance, the nature, and possible substrate preference of the splenocyte Giα coupled PLC is addressed in the second paper.
    Additional Material: 6 Ill.
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  • 4
    ISSN: 0730-2312
    Keywords: G proteins ; sodium metavanadate ; phorbol esters ; dexamethasone ; NaF ; trifluoperizine ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: We have described in the first paper the coupling betweencytosolic Giα and cytosolic PLC activity in a cell free preparation. In order to establish the functional significance of the cytosolic Giα coupled soluble PLC, we examined the effects of Dex, NaF, and trifluopeerizine (TEP) on concanavalin A(Con A)-induced PI-turnover in intact slenocytes and, in parallel, on soluble PLC activity in cytosol preparations. Vytosolic PLC activity was measured with [3H]PIP and [3H]PIP2 as substrates. (1) The con A-induced increase (2-4 fold) in Pl-turnover in intact splenocytes was paralleled by an 1.2-5-fold increase in soluble PLC activity in vitro. Con A administration also increased cytosolic Giα immunoreactivity 3-6-fold as expected if cytosolic Giα was coupled to soluble PLC activation. (2) DEX (10-7 M), administered 6 h prior to Con A administration inbited the Con A-induced increase in Pl-turnover in intact splenocytes. This was paralleled by DEX inhibition of the Con A-induced increase in soluble PLC activity measured in vitro and cytosolic Giα imunoreactivity. (3) We have demonstrated in the first paper that NaF and TEP inhibited soluble PLC activity. Here we show that NaF and TFP inhibited the Con A-induced increase in PI-turnover extending the similarities between soluble PLC activity and Con A- Stimulated PLC Activity in intact splenocytes. (4) In order to examine Whether or not the Con A-induced PLC activity and Con A-stimulated PLC activity in intact splenocytes. (4) In order to examine Whether or not the Con A-induced PLC was similar to PLCγ, we measured PI-turnover induced by Con A or BaVO3 in combination with DEX and PMA. Whereas the Con A-induced PI-turnover was significantly inhibited (40-60%) by DEX, the NaVO3 -induced PI-turnover was not affected by DEX. The Con A-induced PI-turnover was not affected by PMA (50nM), But the NaVO3-induced Pi-turnover was increased over 2-fold PMA (50nM), suggesting that the Con A-induced PLC in intact splenocytes is different from NaVO3-induced PLC. Based on these results a model for the sequential activation of substrate-specific PLCs in splenocyte by mitogen is presented.
    Additional Material: 5 Ill.
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  • 5
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Short (5 days)-to long-term (4 months) corticosterone (CORT) administration by injection, pellet implantation, or in the drinking water decreased glial fibrillary acidic protein (GFAP) by 20–40% in hippocampus and cortex of intact rats. In contrast to CORT, adrenalectomy (ADX) caused elevations (50–125%) in hippocampus and cortex GFAP within 12 days of surgery that persisted for at least 4 months. CORT replacement of ADX rats decreased GFAP amount in hippocampus and cortex. The effects of long-term CORT and ADX on GFAP in hippocampus and cortex were also seen in striatum, midbrain, and cerebellum, findings suggestive of brain-wide adrenal steroid regulation of this astrocyte protein. The changes in GFAP amount due to CORT and ADX were paralleled by changes in GFAP mRNA, indicating a possible transcriptional or at least genomic effect of adrenal steroids. Glucocorticoid regulation of GFAP was relatively specific; it could not be generalized to other astrocyte proteins or other major structural proteins of neurons. The negative regulation of GFAP and GFAP mRNA by adrenal steroids suggested that increases in GFAP that result from brain injury may be attenuated by glucocorticoids. However, chronic CORT treatment of intact rats did not reverse or reduce the large increases in GFAP caused by trauma-or toxicant-induced brain damage. Thus, glucocorticoids and injury appear to regulate the expression of GFAP through different mechanisms. In contrast to the lack of effects of CORT on brain damage-induced increases in GFAP, CORT treatment begun in 2-week ADX rats, after an increase in GFAP had time to occur, did reverse the ADX-induced increase in GFAP. These results suggest that the increase in GFAP resulting from ADX is not mediated through an injury-linked mechanism.
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  • 6
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: We assessed the effects of cold and isolation stress on arginine vasopressin (AVP) mRNA in the paraventricular (PVN) and supraoptic (SON) nuclei of the hypothalamus. Vasopressin mRNA levels were determined by in situ hybridization histochemistry at the cellular level. In posterior magnocellular neurons of the PVN isolation stress for 7 or 14 days increased vasopressin mRNA levels 28 and 29%, respectively, compared to group-housed controls. No significant alterations in vasopressin gene expression were observed in the SON after 7 or 14 days of isolation stress. Scattered magnocellular AVP mRNA-expressing cells of the medial parvocellular PVN showed increases of 19 and 34% after 7 and 14 days of isolation, respectively. We also studied the effect of cold or combined cold and isolation stress on vasopressin gene expression in the PVN and SON. Cold stress for 3 h daily for 4 consecutive days increased AVP mRNA levels in the posterior magnocellular PVN by 15%. Cold-isolated animals showed an increase of 21%. No significant effect on AVP mRNA levels in the SON was observed. In contrast to the posterior magnocellular PVN, cold or cold-isolation stress increased AVP mRNA in magnocellular neurons of the medial parvocellular region of the PVN by 25 and 43%, respectively, relative to control rats. These results suggest that psychological and metabolic stress may be added to the list of stressors that activate the hypothalamo–neurohypophysial system.
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  • 7
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Sex differences were investigated in cholinergic neurons of the septal-diagonal band region of adult rats subjected to neonatal treatment with 3,3′,5-triiodo-L-thyronine (T3). Neonatal hyperthyroidism resulted in a 44% increase in specific activity of choline acetyltransferase (ChAT; EC 2.3.1.6) in adult male rat septal-diagonal band region, whereas no change in ChAT activity could be detected in either dorsal or ventral hippocampus. An increase in muscarinic cholinergic receptors, as measured by [3H]quinu-clidinyl benzilate ([3H]QNB) binding, was discovered in both septum-diagonal band and dorsal hippocampus of the T3-treated male rats. Immunohistochemistry in the septal-diagonal band region indicated a more intense staining in the neonatally T3-treated adult male rats than in controls, with larger and more abundant ChAT-positive and nerve growth factor receptor (NGF-R)-positive varicosities. ChAT immunocytochemistry showed a substantial decrease in cell body area in the medial septum and in the vertical limb of the diagonal band of T3-treated male rats, while cell density increased twofold. Female littermates subjected to the same treatment showed no changes in any of the biochemical or immunohistochemical cholinergic markers. Only in the medial septum was morphology significantly altered in the female T3-treated rats in that ChAT-positive cell body area increased. These results indicate a marked sexual variation in the septal-diagonal band region with respect to the sensitivity of postnatally developing cholinergic neurons to the actions of excess thyroid hormone.
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  • 8
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Manipulation of the hypothalamic-pituitary-adrenal axis selectively alters α-adrenergic potentiation of the cyclic AMP response to β-adrenergic receptor stimulation in rat cerebral cortex. Calcium has been implicated in this α-receptor-mediated response, which may involve activation of phospholipases A2 and C and/or calmodulin-dependent adenylate cyclase. We therefore investigated the effects of stress and corticosterone (CORT) on membrane calmodulin-dependent adenylate cyclase and noradrenaline-stimulated cyclic AMP accumulation in brain slices. Repeated stress for 21 days selectively attenuated the adenylate cyclase response to calcium/calmodulin in cerebral cortex membranes, without affecting basal or forskolin-stimulated enzyme activity. There was no such effect in hippocampal membranes. The same pattern of response was elicited by daily CORT injection (50 mg/kg s.c.) for 21 days, while vehicle injection had no effect. CORT in the drinking water (400 μg/ml) elicited the same reduction of body weight as CORT injections, but had no effect on calmodulin adenylate cyclase. In parallel with calmodulin adenylate cyclase, cyclic AMP accumulation elicited by noradrenaline in slices of cerebral cortex was suppressed by both stress and daily CORT injections, with smaller effects observed with CORT in the drinking water. Unlike calmodulin adenylate cyclase, noradrenaline-stimulated cyclic AMP accumulation in hippocampus showed the same suppression as that in cerebral cortex. These results are discussed in relation to the differential mode of coupling of α-adrenergic receptors to cyclic AMP-generating systems between brain regions. Glucocorticoid-mediated suppression of noradrenaline-stimulated cyclic AMP accumulation and calmodulin-dependent adenylate cyclase may represent parallel effects of the hormone, but their co-occurrence in cerebral cortex may also indicate some functional coupling and compartmentalization. The ability of daily CORT injection to mimic the effects of repeated stress, but inability of CORT ingestion at high doses in the drinking water to do so, suggests that the time course of CORT elevation and the coincidence of some type of stress may be important for the suppression of cyclic AMP-generating systems in brain.
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  • 9
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: We measured proenkephalin (PEK) mRNA levels in the anterior and medial aspects of the caudate-putamen (CPU) and in the nucleus accumbens (NAc) of the rat by in situ hybridization histochemistry after chronic treatment for 21 days with typical (haloperidol and prolixin) and atypical (molindone, thioridazine, and clozapine) neuroleptics. Chronic administration with these drugs resulted in PEK mRNA levels that were 60–80% higher than controls in the anterior and medial aspects of the CPU but only 25–30% over controls in the NAc. All three atypical neuroleptics studied increased PEK mRNA in the following order: anterior-CPU, thioridazine 〉 clozapine and molindone; medial-CPU, thioridazine and molindone 〉 clozapine; and NAc, thioridazine 〉 〉 molindone and clozapine. Chronic treatment with the specific dopamine D2 antagonist sulpiride also caused elevation in PEK mRNA levels in all three brain regions studied whereas the specific serotonin S2 receptor blocker, cinanserin, had no significant effects on PEK mRNA levels. These results are consistent with the hypothesis that elevated levels of the enkephalins in the mesolimbic system may be necessary for antipsychotic activity. They also support the idea that the undesirable motoric signs and symptoms observed after chronic treatment with typical neuroleptics may not be the result of increased levels of enkephalins in the basal ganglia because atypical neuroleptics which are almost totally devoid of these side effects caused similar increases in PEK mRNA in the CPU.
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  • 10
    ISSN: 1365-2826
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Sex differences in the induction of cytosolic progestin receptors (CPR) by estrogen priming were correlated with the sex differences in behavioral responses. We evaluated the temporal relationship between CPR in several brain regions and pituitary and the time-course of 17β-estradiol (E2) activation of female sexual behavior in gonadectomized male and female rats implanted with subcutaneous E2 Silastic capsules for 6 h, 24 h and 48 h. Both CPR levels and mating behavior increase monotonically with the time of E2 exposure. Induction of CPR was observed in the periventricular region of the preoptic area (PVPOA), arcuate nucleus (ARC), ventromedial nuclei (VMN) and pituitary in both sexes. A small induction of CPR was found in parietal cortex. The VMN in female rats showed a significant E2-induced CPR increase at all times of exposure, while in male rats this induction was only significant after 24 h. Significant sex differences in absolute CPR levels and E2-induced receptors were found in the following structures: VMN, 18 h after 6 h of E2 treatment and after 24 h and 48 h of continuous E2 exposure; PVPOA, only after 48 h of continuous E2 exposure; ARC at 24 h and 48 h; and pituitary after all E2 treatment. Mating behavior was tested under two conditions: E2 alone (2 h after removal of E2 capsules) and E2+progesterone (2 h after a progesterone injection given 10 min after concluding the first test). Receptivity was first observed after 24 h E2 exposure in female rats, whereas in male rats a small response appeared only after 48 h of E2 exposure. After progesterone priming, the time of E2 exposure necessary for expression of female sexual behavior was reduced to 6 h in females and 24 h in males. The appearance of mating behavior appears to follow that of inducible CPR in the VMN in both sexes. In addition, the CPR levels associated with the first receptivity either by male rats (16.6 fmol/mg protein) or female rats (15.3 fmol/mg protein) are very similar suggesting the presence of a threshold level controlling the expression of feminine sexual behavior. It is likely that inhibitory neural input plays a role in determining the threshold level of E2-induced CPR, which is sufficient to trigger lordosis behavior.
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