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Biomedical subjects

E Costa

Publications and source records attributed to E Costa.

At least 307 records · Page 17Linked to original sources
PubMed1986

Maprotiline: an antidepressant with an unusual pharmacological profile.

Maprotiline, which differs from other typical tricyclic antidepressants for its tetracyclic structure, is a highly selective inhibitor of norepinephrine reuptake. Despite its in vitro and in vivo inhibitory activity on NE uptake, 21 repeated daily injections of maprotiline (20 mg/kg i.p.) neither attenuated the norepinephrine-stimulated cAMP accumulation nor reduced the number of beta adrenergic recognition sites in rat frontal cortex. Also, the number of brain serotonin2 recognition sites labeled by [3H]ketanserin remained virtually unchanged in rats receiving 21 daily injections of maprotiline. [3H]Desmethylimipramine and [3H]mianserin specific binding sites were also unmodified by repeated maprotiline injections. However, after 3 weeks of daily administrations, maprotiline elicited a significant decrease in the number of [3H]flunitrazepam binding sites and a decrease in the apparent affinity of [3H]beta-carboline ethylester binding to crude synaptic membranes prepared from hippocampal and hypothalamic homogenates. These changes appear to be unrelated to modifications in the concentration of endogenous gamma-aminobutyric acid present in the membrane preparation, since the addition of 100 microM bicuculline to the incubation mixture decreases [3H]flunitrazepam binding to the same extent in saline- and maprotiline-treated rats. It is suggested that repeated maprotiline injections may elicit an increase in the hypothalamic and hippocampal tissue levels of an endogenous substance(s) which binds to the benzodiazepine/beta-carboline recognition sites.

Animals↗
PubMed1986

The activation of inositol phospholipid metabolism as a signal-transducing system for excitatory amino acids in primary cultures of cerebellar granule cells.

L-Glutamic, L-aspartic acids and a number of their structural analogs, including quisqualic, kainic, ibotenic, quinolinic, and N-methyl-D-aspartic (NMDA) acids, increase inositol phospholipid hydrolysis when added to primary cultures of cerebellar granule cells, as is reflected by an enhanced formation of 3H-inositolmonophosphate (3H-IP1) in the presence of Li+. L-Glutamic acid also enhances the formation of the initial products of inositol phospholipid hydrolysis, 3H-inositol di-(3H-IP2) and triphosphate (3H-IP3). In the absence of extracellular Ca2+, L-glutamic acid fails to enhance 3H-IP1 formation, but still increases 3H-IP2 and 3H-IP3 formation. The stimulation of 3H-IP1 formation elicited by L-glutamic acid is reduced by DL-2-amino-5-phosphonovaleric acid (APV) and gamma-glutamylglycine and, to a lesser extent, by 2,3-cis-piperidindicarboxylic acid (PDA). The stimulation of 3H-IP1 formation by kainic acid is antagonized by PDA and gamma-glutamylglycine, but it is almost unaffected by APV. The increase in 3H-IP1 formation elicited by quisqualic acid is not reduced by any of the dicarboxylic amino acid receptor antagonists that we have tested. We conclude that different subtypes of excitatory amino acid recognition sites are associated with inositol phospholipid metabolism in primary cultures of cerebellar granule cells.

Amino Acids↗
PubMed1986

5-Hydroxytryptamine2 receptors coupled to phospholipase C in rat aorta: modulation of phosphoinositide turnover by phorbol ester.

In rat aorta, 5-hydroxytryptamine (5-HT) stimulated phosphoinositide (PI) turnover and contraction (EC50 = 10 +/- 3 microM); these two responses were highly correlated (r = 0.95; P less than .01). We have characterized the inhibitory potency of a variety of 5-HT-antagonists against the stimulation of PI turnover elicited by 5-HT. Classic 5-HT2 antagonists mianserin, ketanserin, metergoline and pizotifen were found to inhibit this response in the low nanomolar range; amitryptiline and haloperidol were 10- to 20-fold less potent. The alpha-1 receptor antagonist, prazosin, was inactive in micromolar concentrations. The potency of the 5-HT2 antagonists was correlated with their ability to displace [3H] ketanserin binding from rat frontal cortex membranes (r = 0.90; P less than .05). The tumor promoter phorbol dibutyrate was found to inhibit 5-HT-stimulated PI turnover at low nanomolar concentrations whereas the biologically inactive substance 4-alpha-phorbol was ineffective. Pretreatment of rat aorta with phorbol dibutyrate at concentrations that inhibited 5-HT-induced PI turnover also attenuated the aortic contraction induced by 5-HT in the presence of a calcium channel blocker nitrendipine. Our results suggest that phorbol esters may desensitize 5-HT2-receptor-mediated PI turnover and contraction of rat aorta, possibly via an activation of protein kinase C.

Animals↗
PubMed1985

Biochemical and immunohistochemical evidence for the presence of motilin in pig cerebellum.

The presence of motilin in rat and porcine cerebellum was investigated by using high performance liquid chromatography (HPLC) coupled with radioimmunoassay or immunohistochemistry. The antibodies used for this study were raised against synthetic gastrointestinal porcine motilin, which is, so far, the only known sequence of this peptide. The results obtained show the presence of a sharp peak of motilin-like immunoreactivity after HPLC of porcine cerebellum extracts, with an elution time corresponding to that of synthetic porcine motilin. Motilin-like immunoreactivity was also detected immunohistochemically in porcine cerebellum. However no motilin-like immunoreactivity was detected in rat cerebellum biochemically or immunohistochemically. This finding suggests that if a motilin-like neuropeptide is present in rat cerebellum, its molecular form differs from that present in porcine cerebellum.

Animals↗
PubMed1985

Diazepam-binding inhibitor: a neuropeptide located in selected neuronal populations of rat brain.

An endogenous polypeptide of rat brain has been identified that is capable of displacing 1,4-benzodiazepines and the esters of the 3-carboxylic acid derivatives of beta-carbolines from their specific synaptic binding sites. This polypeptide was termed diazepam-binding inhibitor (DBI). Previous studies have shown that DBI injected intraventricularly in rodents elicits "proconflict" responses and antagonizes the "anticonflict" action of benzodiazepines. An antiserum to this peptide, directed toward an immunodeterminant near its amino terminus, makes it possible to detect, measure, and study the neuronal location of this peptide in rat brain. In the rat cerebral cortex, DBI immunoreactivity is located in neurons that are not GABAergic (GABA, gamma-aminobutyric acid); in the cerebellum and hippocampus, however, it might be present also in GABAergic neurons.

Animals↗
PubMed1985

Different effects of serotonin antagonists on 3H-mianserin and 3H-ketanserin recognition sites.

In minces prepared from the frontal cortex of rats treated with ketanserin (10 mg/kg i.p.) or mianserin (5 mg/kg i.p.) twice daily for 21 days, the Vmax of the adenylate cyclase stimulated by NE (100 microM) is attenuated, suggesting that ketanserin and mianserin share with a number of antidepressants the ability to attenuate the adenylate cyclase stimulation by NE. Ketanserin, given with the above mentioned dose schedule for 7 consecutive days, reduced the Bmax of 5HT2 recognition sites but failed to change either the Bmax or the apparent Kd of H-mianserin binding. A significant decrease in the Bmax of 5HT2 binding sites is elicited also by a single injection of mianserin (1). This drug also down-regulates its own binding when given twice daily for 3 weeks. From this and other information (2,3), it is concluded that ketanserin and mianserin bind to distinct recognition sites. The possibility that 5HT2 and mianserin recognition sites are functionally related and that serotonergic synapses are modulated by multiple chemical signals might be considered.

Animals↗
PubMed1985

Different coupling of excitatory amino acid receptors with Ca2+ channels in primary cultures of cerebellar granule cells.

Cerebellar granule cells in primary culture express receptors for excitatory amino acids. The activation of these receptors results in an increased uptake of Ca2+, however, the effects are different depending on the agonists used. Aspartate, NMDA and ibotenate are active only in depolarized conditions, whereas kainate and glutamate activate Ca2+ uptake independently from depolarization. The results indicate the presence of two receptor types: kainate recognition site coupled with voltage-independent Ca2+ channels and NMDA recognition site coupled with voltage-dependent Ca2+ channels.

Amino Acids↗
PubMed1985

Dihydropyridines change the uptake of calcium induced by depolarization into primary cultures of cerebellar granule cells.

The uptake of calcium (Ca++) into cerebellar granule cells in primary culture was increased by depolarizing the cells with either 60 mM KC1 or veratridine. Nitrendipine, at concentrations of 100 nM or greater, antagonized approximately 40 percent of the depolarization induced Ca++ uptake. The half maximal concentration of nitrendipine was 7nM. Furthermore, another dihydropyridine derivative, BAY K 8644 enhanced the uptake of Ca++ and in the presence of nitrendipine, this facilitation of Ca++ uptake was reduced. Thus, these data indicate the existence of voltage dependent Ca++ channels which are sensitive to dihydropyridines in primary cultures of cerebellar granule cells.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1985

Release of high molecular weight forms of met5-enkephalin-arg6-gly7-leu8 from rat brain.

The release of various molecular weight forms of met5-enk-arg6-gly7-leu8 (MERGL) from slices prepared from rat medulla-pons and hypothalamus was studied. The release of MERGL-IR from both medulla-pons and hypothalamic slices was elevated four- to ten-fold in response to potassium depolarization. Gel of 8 to 10 kilodalton MERGL-IR peptide(s), as well as MERGL itself, were released in response to stimulation with 50 mM K+.

Animals↗
PubMed1985

Isolation, sequencing, synthesis, and pharmacological characterization of two brain neuropeptides that modulate the action of morphine.

Two peptides that crossreact with an antiserum raised against Phe-Met-Arg-Phe-NH2 were purified from bovine brain extract. Their structures were determined to be Ala-Gly-Glu-Gly-Leu-Ser-Ser-Pro-Phe-Trp-Ser-Leu-Ala-Ala-Pro-Gln-Arg-Phe- NH2 and Phe-Leu-Phe-Gln-Pro-Gln-Arg-Phe-NH2. The sequences were determined by gas-phase sequencing, except for the COOH-terminal phenylalaninamides. These were assigned on the basis of the reactivity of the peptides with the anti-Phe-Met-Arg-Phe-NH2 antiserum, which appears to recognize the determinant -Arg-Phe-NH2. Both peptides were synthesized, and the synthetic peptides were found to have the same HPLC retention times as the endogenous Phe-Met-Arg-Phe-NH2-immunoreactive peptides, thus confirming the assignment of phenylalaninamide to the COOH-terminal positions. Both of the synthetic peptides were found to decrease tail-flick latency in rats, and the octapeptide was more active than the octadecapeptide. The octapeptide was found also to attenuate the prolongation of the tail-flick latency induced by morphine.

Amino Acid Sequence↗
PubMed1985

5-Hydroxytryptamine uptake and imipramine binding sites in neurotumor NCB-20 cells.

NCB-20 cells (neuroblastoma X fetal Chinese hamster brain hybrids) are equipped with a [3H]5-hydroxytryptamine [( 3H]5-HT) uptake system and [3H]imipramine recognition sites. Approximately 80% of the radioactivity taken up by cells incubated with [3H]5-HT was identified with 5-HT. [3H]5-HT uptake was temperature-dependent, partially sodium-dependent, saturable (Km = 7.3 +/- 0.6 microM; Vmax = 2.0 +/- 0.6 pmol/min/mg), and inhibited by clomipramine, imipramine, fluoxetine, and desipramine, but not by iprindole, mianserin, or opipramol. Lineweaver-Burk plots showed a competitive type of inhibition by imipramine and fluoxetine. [3H]5-HT uptake was not inhibited by nisoxetine or benztropine. [3H]Imipramine binding sites had a KD of 12 +/- 2 nM and a Bmax of 22 +/- 7 pmol/mg protein. The binding was sodium-sensitive although to a lesser extent than that found with brain membranes. Imipramine binding was displaced by tricyclic antidepressants with the following order of potency: clomipramine greater than imipramine greater than fluoxetine greater than desipramine much greater than iprindole = mianserin greater than opipramol. These results suggest that imipramine binding sites are present together with the 5-HT uptake sites in NCB-20 cells and that these sites interact functionally but are different biochemically.

Animals↗
PubMed1985

Ca2+ and phospholipid-dependent protein kinase activity and phosphorylation of endogenous proteins in bovine adrenal medulla.

Soluble and membrane fractions of bovine adrenal medulla contain several substrates for the Ca2+/phospholipid-dependent and cyclic AMP-dependent protein kinases. The phosphorylation of soluble proteins (36 and 17.7 kilodaltons) and a membrane protein (22.5 kilodaltons) showed an absolute requirement for the presence of both Ca2+ and phosphatidylserine; other substrates showed less stringent phosphorylation requirements and many of these proteins were specific for each of the protein kinases. The Ca2+/phospholipid-dependent phosphorylation was rapid, with effects seen as early as at 30 s of incubation. Measurement of enzyme activities with histone H1 as an exogenous substrate demonstrated that the Ca2+/phospholipid-dependent protein kinase was equally distributed between the soluble and membrane fractions whereas the cyclic AMP-dependent enzyme was predominantly membrane-bound in adrenal medulla and chromaffin cells. The activity of the soluble Ca2+/phospholipid-dependent protein kinase of adrenal medulla was found to be about 50% of the enzyme level present in rat brain, a tissue previously shown to contain a very high enzyme activity. These results suggest a prominent role for the Ca2+/phospholipid-dependent protein kinase in chromaffin cell function.

Adrenal Medulla↗
PubMed1985

GABA-modulin: a synaptosomal basic protein that differs from small myelin basic protein of rat brain.

GABA-modulin, a basic protein that allosterically inhibits the high-affinity binding of GABA to its recognition sites, has been extracted and purified from the synaptosomal fraction of rat brain where it represents approximately 0.5% of the total synaptosomal proteins. GABA-modulin has characteristics in common to the class of highly basic proteins isolated from myelin, in particular to the rat small myelin basic protein (SMBP). However, GABA-modulin is located selectively in synaptosomes, whereas the SMBP is located in myelin. Moreover, synaptosomal GABA-modulin is different from SMBP in amino acid composition (it contains more Glx and Lys and fewer Arg residues) and in apparent molecular weight (17,000 and 15,000 for GABA-modulin and SMBP, respectively). Synaptosomal GABA-modulin fails to bind [3H]muscimol per se but noncompetitively inhibits (IC30 approximately 0.5 microM) the binding of [3H]muscimol to purified synaptic membranes. Cyanogen bromide treatment generated a 13,000 MW major fragment from both SMBP and GABA-modulin. These two fragments were compared and showed differences in amino acid composition and sequence. Moreover, the peptide maps generated from GABA-modulin and SMBP by trypsin and staphylococcal V8 protease digestion are different. The high concentration of GABA-modulin in synaptosomal membranes, its high potency in the inhibition of GABA binding, and its neuronal specificity suggest that GABA-modulin plays an important role in neuronal membrane function linked to the modulation of GABA and perhaps other neurotransmitter receptors.

Amino Acids↗
PubMed1985

Histamine-containing peripheral neuronal and endocrine systems.

An immunohistochemical method was developed to detect histamine in tissues. The aim of this study was to reveal the cellular stores of histamine in the gastrointestinal tract, pituitary, and adrenal gland. Histamine-containing nerve fibers were found in both rat and guinea pig gut. The origin of at least some of these fibers in the rat ileum was the submucous ganglion cell layer. In the rat stomach, numerous enterochromaffin-like cells exhibited histamine immunofluorescence, and endocrine cells in the ileum and jejunum contained histamine. Only mast cells contained histamine in the neurohypophysis. A large number of process-bearing cells in the guinea pig but not in the rat adrenal medulla contained histamine. The study shows that histamine is present in peripheral nerves and endocrine cells in addition to mast cells, and may function as a neurotransmitter or hormone.

Adrenal Glands↗