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Biomedical subjects

E Costa

Publications and source records attributed to E Costa.

At least 289 records · Page 16Linked to original sources
PubMed1986

Analgesic activity and release of [MET5]enkephalin-Arg6-Gly7-Leu8 from rat spinal cord in vivo.

Rat spinal cord contains the opioid peptide including [Met5]enkephalin-Arg6-Gly7-Leu8 (YGGFMRGL) and a higher molecular weight (HMW) immunoreactive peptide which is an N-terminal extended molecular form of YGGFMRGL. Since a high proportion of tissue immunoreactivity resides in the HMW component we have determined whether this form is released during perfusion of the spinal cord subarachnoid space in vivo while (1) electrically stimulating the sciatic nerves bilaterally or (2) superfusing with substance P. We have found that YGGFMRGL and the HMW immunoreactivity are released by both types of stimuli. The HMW material appeared to be the more stable of the two species of immunoreactivity; its presence in the superfusate was more consistently observed than that of YGGFMRGL itself. Injection of YGGFMRGL into the spinal subarachnoid space in chronically catheterized rats produced a suppression of the tail-flick response. This effect of YGGFMRGL was reversed by naloxone suggesting an action mediated by spinal opiate receptors. These data suggest that YGGFMRGL plays an integral role in the neurotransmission process between spinal neurons storing enkephalin and other neurons. The possibility that enkephalin-mediated neurotransmission includes multiple chemical signals can be entertained.

Analgesics↗
PubMed1986

Diazepam-binding inhibitor. A brain neuropeptide present in human spinal fluid: studies in depression, schizophrenia, and Alzheimer's disease.

Diazepam-binding inhibitor is a novel peptide purified to homogeneity from rat and human brain. Diazepam-binding inhibitor is present, though not exclusively, in gamma-aminobutyric acid (GABA)-containing neurons where it is believed to inhibit GABAergic neurotransmission mediated by GABA by binding to the benzodiazepine-GABA receptor complex. Since an impairment of central GABAergic tone has been postulated to be associated with a number of neuropsychiatric disorders, we measured human diazepam-binding inhibitor immunoreactivity in the cerebrospinal fluid (CSF) of patients suffering from endogenous depression, schizophrenia, and dementia of the Alzheimer's type. Patients with major depression had significantly higher concentrations of human diazepam-binding inhibitor immunoreactivity in CSF when compared with age- and sex-matched normal volunteers, while no difference in CSF diazepam-binding inhibitor immunoreactivity was found in schizophrenics or patients with dementia of the Alzheimer's type when compared with controls. The possibility is discussed that the increased CSF human diazepam-binding inhibitor immunoreactivity observed in depressed patients may represent a functional disinhibition of GABAergic neurotransmission associated with depression.

Adult↗
PubMed1986

Changes in the dynamic state of brain proenkephalin-derived peptides during amygdaloid kindling.

The dynamic state of the proenkephalin (PE) gene products during and after development of amygdaloid kindling was assayed by monitoring changes of the accumulation of PE mRNA and changes in proenkephalin-related peptides. A parallel determination of PE mRNA and peptides from the same sample was conducted in this study. Electrical stimulation of the amygdala causes early increases in the PE mRNA content in that structure and in the hippocampus. Other areas related with the amygdaloid complex do not exhibit such an early increase, but this alteration occurs when the kindling process is fully established. Enkephalin content increases early in amygdala and hippocampus presumably owing to an increase in synthesis rate. Also, the enkephalin content of areas connected with amygdala and hippocampus such as the entorhinal cortex, the nucleus accumbens, and the frontal and occipital cortex exhibits an increase. A clear tendency towards normalization is observed after a recovery period of 2-3 months. Rekindling of the animals after this recovery period does not elicit a similar pattern of changes in the dynamic state of enkephalin system, even though the animals rekindle with just one single stimulation. The present data suggest that the enkephalinergic neurons participate in the development and spreading of kindling phenomena after amygdaloid stimulation, but they do not seem to play any role in mediating maintenance of the kindling state.

Amygdala↗
PubMed1986

Pharmacological modulation of GABAergic transmission in cultured cerebellar neurons.

GABA activates specific ion channels in post-natal cerebellar neurons in primary culture generating Cl- currents that can be recorded with the whole-cell patch-clamp technique. Evoked and spontaneous GABA-mediated synaptic activity can be recorded from cells kept in culture for a few days. Benzodiazepine and beta-carboline derivatives which bind with high affinity to the domains for allosteric regulation of GABA receptors facilitated and inhibited directly applied GABA responses and synaptically evoked Cl- currents recorded under voltage-clamp.

Animals↗
PubMed1986

Serine-O-phosphate, an endogenous metabolite, inhibits the stimulation of inositol phospholipid hydrolysis elicited by ibotenic acid in rat hippocampal slices.

Serine-O-phosphate (PS) inhibits the accumulation of 3H-inositolmonophosphate elicited by ibotenic acid in rat hippocampal slices incubated in the presence of 7 mM Li+. This inhibition is concentration- dependent and stereoselective, L-PS being 5 fold more potent than D-PS. Among different structural analogues of PS, only L-serine weakly antagonizes the action of ibotenic acid, whereas phosphorylcholine, phosphorylethanolamine and phosphothreonine are inactive even at high concentrations. These results are consistent with the hypothesis that L-PS may act as an endogenous regulator of excitatory amino acid receptor function.

Animals↗
PubMed1986

Peripheral and central origin of Phe-Met-Arg-Phe-amide immunoreactivity in rat spinal cord.

Phe-Met-Arg-Phe-amide immunoreactivity (FMRF-NH2-IR) is highly concentrated in the dorsal horn of rat spinal cord, and particularly in nerve terminals of lamina I. In order to establish the location of the cell bodies of the lamina I terminals containing FMRF-NH2-IR, we measured by radioimmunoassay the FMRF-NH2-IR in sensory ganglia and in spinal roots. FMRF-NH2-IR was found in both tissues, and reverse-phase HPLC analysis revealed that both tissues contain the same molecular forms that are also present in the spinal cord. Lumbo-sacral rhizotomy induced a 50% decrease of FMRF-NH2-IR in the lumbar segment of the spinal cord suggesting that at least a portion of the FMRF-NH2-IR present in this tissue is of peripheral origin. Transection of the spinal cord at the midthoracic level induced a 20-50% decrease of FMRF-NH2-IR in the lumbar segment of the spinal cord suggesting also the presence of FMRF-NH2-IR in descending pathways.

Animals↗
PubMed1986

Cloning and expression of cDNA for human diazepam binding inhibitor, a natural ligand of an allosteric regulatory site of the gamma-aminobutyric acid type A receptor.

Diazepam binding inhibitor (DBI) is a protein that displaces ligands bound to the beta-carboline/benzodiazepine recognition site, an allosteric modulatory site of the type A gamma-aminobutyric acid receptor complex. An incomplete rat cDNA clone coding for DBI was isolated. This rat sequence was utilized to identify a cDNA clone that encoded the entire 104 residues of human DBI. This sequence was engineered for expression in E. coli, and recombinant DBI exhibits identical biochemical and antigenic characteristics of natural human DBI. DBI is encoded by a multigene family of at least five members, but a single gene appears to account for the majority of DBI expression. DBI is expressed in a tissue-specific manner. Expression is found in central nervous system tissues and appears to extend to peripheral tissues rich in the peripheral type of high-affinity benzodiazepine recognition sites. The role of these sites and DBI in adrenal gland, testis, and kidney remains to be determined.

Amino Acid Sequence↗
PubMed1986

Modulation of gamma-aminobutyric acid-mediated inhibitory synaptic currents in dissociated cortical cell cultures.

Inhibitory gamma-aminobutyric acid-mediated synaptic currents were studied in dissociated primary cultures of neonatal rat cortex with the whole-cell patch-clamp technique. Immunocytochemical staining of the cultures showed the presence of a large number of glutamic acid decarboxylase-containing neurons, and electrical stimulation of randomly selected neurons produced in many cases chloride-mediated and bicuculline-sensitive inhibitory synaptic currents in postsynaptic cells. The amplitude and decay time of the inhibitory synaptic currents were increased by flunitrazepam and decreased by the beta-carboline derivative methyl 6,7-dimethoxy-4-ethyl-beta-carboline-3-carboxylate, two high-affinity ligands for the allosteric regulatory sites of gamma-aminobutyric acid receptors. The imidazobenzodiazepine Ro 15-1788, another high-affinity ligand of the gamma-aminobutyric acid receptor regulatory sites that has negligible intrinsic activity, blocked the action of flunitrazepam and beta-carboline. However, Ro 15-1788 also increased the decay rate of the inhibitory synaptic currents. This might suggest that an endogenous ligand for the benzodiazepine-beta-carboline binding site is operative in gamma-aminobutyric acid-mediated synaptic transmission.

Animals↗
PubMed1986

Study of an octadecaneuropeptide derived from diazepam binding inhibitor (DBI): biological activity and presence in rat brain.

An endogenous brain neuropeptide with 104 amino acid residues that modulates gamma-aminobutyric acid receptor function was termed DBI because it displaces diazepam from its specific brain binding sites. Tryptic digestion of DBI generates an octadecaneuropeptide (ODN) that is more potent than the parent compound in the displacement of specifically bound beta-[3H]carboline-3-carboxylate methyl ester [( 3H]BCCM) and in proconflict action (Vogel test in thirsty rats). The proconflict action of ODN is antagonized by the imidobenzodiazepinone Ro 15-1788, which is a specific antagonist of beta-carboline and benzodiazepine recognition sites. The ODN amino acid sequence is Gln-Ala-Thr-Val-Gly-Asp-Val-Asn-Thr-Asp-Arg-Pro-Gly-Leu-Leu-Asp-Leu-Lys. The pharmacological properties associated with this sequence were confirmed by comparing the activity of ODN generated from tryptic digestion of DBI with that of ODN obtained by synthesis. Amidation of the terminal lysine of ODN produces a peptide (ODN-NH2) devoid of pharmacological activity. Three peptides containing the COOH-terminal segment of ODN were synthesized. All these peptides [Arg-Pro-Gly-Leu-Leu-Asp-Leu-Lys (octapeptide), Pro-Gly-Leu-Leu-Asp-Leu-Lys (heptapeptide), and Gly-Leu-Leu-Asp-Leu-Lys (hexapeptide)] express the displacing and proconflict actions of ODN. In primary cultures of cerebellar granule cells of rat, DBI, ODN, octapeptide, heptapeptide, and hexapeptide preferentially displace [3H]BCCM over [3H]flunitrazepam; moreover, they displace bound [3H]BCCM completely but [3H]flunitrazepam only by 50%. These data suggest that ODN includes a specific ligand for the gamma-aminobutyric acid receptor regulatory site occupied by beta-carbolines. Using rabbit antibodies directed against the NH2-terminal portion of ODN, we detected ODN-like material in rat brain homogenates. However, whether this material is identical to the ODN generated by tryptic digestion of DBI remains to be established.

Amino Acid Sequence↗
PubMed1986

Permissive effect of dexamethasone on the increase of proenkephalin mRNA induced by depolarization of chromaffin cells.

In cultured bovine chromaffin cells, changes in the dynamic state of enkephalin stores elicited experimentally were studied by measuring cellular proenkephalin mRNA, as well as enkephalin precursors and authentic enkephalin content of cells and culture media. In parallel, tyrosine hydroxylase mRNA and catecholamine cell content were also determined. Low concentrations (0.5-100 pM) of dexamethasone increased the cell contents of proenkephalin mRNA and enkephalin-containing peptides. High concentrations of the hormone (1 microM) were required to increase the cell contents of tyrosine hydroxylase mRNA and catecholamines. Depolarization of the cells with 10 microM veratridine resulted in a depletion of enkephalin and catecholamine stores after 24 hr. The enkephalin, but not the catecholamine, content was restored by 48 hr. An increase in proenkephalin mRNA content might account for the recovery; this increase was curtailed by tetrodotoxin and enhanced by 10 pM dexamethasone. Tyrosine hydroxylase mRNA content was not significantly modified by depolarization, even in the presence of 1 microM dexamethasone. Aldosterone, progesterone, testosterone, or estradiol (1 microM) failed to change proenkephalin mRNA. Hence, dexamethasone appears to exert a specific permissive action on the stimulation of the proenkephalin gene elicited by depolarization. Though the catecholamines and enkephalins are localized in the same chromaffin granules and are coreleased by depolarization, the genes coding for the processes that are rate limiting in the production of these neuromodulators can be differentially regulated.

Adrenal Medulla↗
PubMed1986

Excitatory amino acid recognition sites coupled with inositol phospholipid metabolism: developmental changes and interaction with alpha 1-adrenoceptors.

Glutamate, aspartate, ibotenate, and quisqualate activate inositol phospholipid hydrolysis in hippocampal slices prepared from brains of 6- to 8-day-old rats. The stimulation by glutamate and aspartate progressively declines during postnatal development and is negligible after the 24th day of life. In contrast, the stimulation of inositol phospholipid hydrolysis by norepinephrine is low in hippocampal slices from newborn animals and increases during development, reaching mature values after the 35th day of life. In adult hippocampal slices, the stimulation of inositol phospholipid hydrolysis elicited by norepinephrine is inhibited by glutamate in a concentration-dependent fashion. This inhibition can also be brought about by aspartate, 2-amino-4-phosphonobutanoate, and L-phosphoserine, a product of endogenous phosphatidylserine hydrolysis.

Age Factors↗
PubMed1986

Potassium ion facilitation of phosphoinositide turnover activation by muscarinic receptor agonists in rat brain.

In rat hippocampal slices kept in Krebs-Henseleit medium, an increase of K+ ions to 12 mM potentiates the stimulation of phosphoinositide turnover elicited by carbachol and (+/-)-cis-methyldioxolane. Oxotremorine is inactive if tested in Krebs-Henseleit medium but it stimulates by 220% the phosphoinositide turnover when K+ is increased to 12 mM. The K+ facilitation of the carbachol stimulation of phosphoinositide turnover was blocked by pirenzepine, a muscarinic antagonist. This drug was equally potent in inhibiting the carbachol stimulation of phosphoinositide turnover both in normal and 12 mM K+ Krebs medium. This facilitatory effect of K+ appears to be preferential for muscarinic receptors, since it failed to increase the activation of phosphoinositide breakdown induced by norepinephrine and histamine. The K+ potentiation of the muscarinic stimulation of phosphoinositide turnover is not mediated by a release of one of the endogenous neurotransmitters stored in these slices because such a facilitation occurs in Ca2+-deprived Krebs-Henseleit medium and failed to occur following a depolarizing dose of veratrine. Our experiments excluded that K+ facilitates carbachol stimulation of phosphoinositide turnover because it modifies the binding characteristics of muscarinic receptors; however, they cannot exclude that K+ acts at the receptor transducer coupling.

Animals↗
PubMed1986

Coupling of inositol phospholipid metabolism with excitatory amino acid recognition sites in rat hippocampus.

Ibotenate, a rigid structural analogue of glutamate, markedly enhances the hydrolysis of membrane inositol phospholipids, as reflected by the stimulation of [3H]inositol monophosphate formation in rat hippocampal slices prelabeled with [3H]inositol and treated with Li+. Quisqualate, homocysteate, L-glutamate, and L-aspartate also induce a significant (albeit weaker) increase in [3H]inositol monophosphate formation, whereas N-methyl-D-aspartate, kainate, quinolinate, and N-acetylaspartylglutamate are inactive. The increase in [3H]inositol monophosphate formation elicited by the above-mentioned excitatory amino acids is potently and selectively antagonized by DL-2-amino-4-phosphonobutyric acid, a dicarboxylic amino acid receptor antagonist. These results suggest that, in the hippocampus, a class of dicarboxylic amino acid recognition sites is coupled with phospholipase C, the enzyme that catalyzes the hydrolysis of membrane inositol phospholipids.

Animals↗
PubMed1986

Hybridization approaches to the study of neuropeptides.

During the course of evolution, species have increased in complexity, and their nervous systems have evolved correspondingly with an increase in the diversity of their capabilities to respond. Part of that diversity has resulted from an increase in cell types and numbers and their interconnections. In addition, much of it comes from the panoply of neurotransmitters available, of which the neuropeptides represent a major portion. The application of the techniques of molecular biology to the nervous system has led to an appreciation of some of the genetic means by which such diversity can be generated. The cloning and sequencing of peptide precursor genes has shown the existence of gene families, genes with duplications of internal sequences, and genes evolutionarily related to one another, suggesting that one response to the increasing complexity of the organism has been a genetic diversification of the precursor population for peptides. As the precursor genes evolved and thereby provided increasing numbers of peptides, the receptor genes may have evolved simultaneously to provide diversification in the responses to these peptides (for example, the opioid peptide precursors) (Comb et al 1983). The precursor sequences obtained have led not only to the predictions of new peptides but also to the discovery of alternative methods of generating diversity from a single gene. At one extreme, the gene is translated into a polyprotein containing several peptides, which are produced in and released from the same cell. At the other extreme, the nuclear transcript of the gene is differentially spliced such that one peptide is expressed in one tissue and another in a different tissue (Calcitonin-CGRP), or one peptide may be expressed with or without a second peptide in different cells (substance P-substance K). The net result is either one neuron producing a multiplicity of responses to several co-released peptides derived from a polyprotein (POMC or PE) or a tissue- or cell-specificity in terms of which peptide is produced and released. Numerous applications have been made utilizing the cDNA probes generated from the cloning of neuropeptide precursors. Hybridization analyses, including in vitro transcription run-off, have demonstrated that the transcription of neuropeptide genes is regulated by transsynaptic activation of transmitter receptors located in the neuronal membrane, or by hormones, or by as yet unveiled mechanisms. Hybridization techniques have allowed assessment of the dynamic state of neuropeptides functioning as neuromodulators.(ABSTRACT TRUNCATED AT 400 WORDS)

Adrenal Medulla↗
PubMed1986

Inhibition of Met5-enkephalin-Arg6-Phe7 degradation by inhibitors of dipeptidyl carboxypeptidase.

The heptapeptide Met5-enkephalin-Arg6-Phe7 (YGGFMRF) is cleaved at a high rate by tissue peptidases including dipeptidyl carboxypeptidase. The inhibitor, Hoe 498 diacid (2-[N-[(S)-1-carboxy-3-phenylpropyl]-L-alanyl]-(1S,3S,5S)-2-azabicyclo- [3.3.0] octane-3-carboxylic acid), was found to be highly effective in blocking YGGFMRF degradation by a dipeptidyl carboxypeptidase present in a preparation of mouse striatal microsomes. The recovery of YGGFMRF released from rat striatal slices was increased in the presence of Hoe 498 diacid. Furthermore, the recovery of YGGFMRF injected into the caudate was increased in rats pretreated i.p. with Hoe 498 diacid. After i.v. or i.p. injections both Hoe 498 diacid and its prodrug Hoe 498 monoester (2-[N-[(S)-1-ethoxycarbonyl-3-phenylpropyl]-L-alanyl]-(1S,3S,5S)-2- azabicyclo [3.3.0] octane-3-carboxylic acid) were detected in rat cerebrospinal fluid and the dipeptidyl carboxypeptidase activity in cerebrospinal fluid was inhibited. These observations indicate that endogenously released YGGFMRF is protected from degradation by Hoe 498 diacid and that systemically administered Hoe 498 diacid or monoester penetrate the blood-brain barrier and inhibit brain and cerebrospinal fluid dipeptidyl carboxypeptidase activity. This potent inhibitor may be useful to block YGGFMRF inactivation in studies of the pharmacology and physiology of YGGFMRF. It is also possible that some of the cerebral effects of these compounds may be referable to an enhancement of YGGFMRF action in the central nervous system.

Animals↗