Search PubMed⌕ Search

Biomedical subjects

E Costa

Publications and source records attributed to E Costa.

At least 343 records · Page 19Linked to original sources
PubMed1984

A brain octadecaneuropeptide generated by tryptic digestion of DBI (diazepam binding inhibitor) functions as a proconflict ligand of benzodiazepine recognition sites.

An octadecaneuropeptide (ODN) produced by the tryptic digestion of DBI was purified and sequenced and its activity on the Vogel test determined. In vitro ODN displaces 3H-diazepam from specific brain recognition sites and injected intraventricularly in thirsty rats facilitates the onset of behavioral inhibition elicited by punishment. The alpha-amide derivative of ODN is devoid of either action. Evidence is presented suggesting that DBI sequence includes at least two replicas of ODN or one replica of ODN and a fragment with similar if not identical amino acid sequence but identical biological activity.

Amino Acid Sequence↗
PubMed1984

Proglumide prevents and curtails acute tolerance to morphine in rats.

The antagonism of the antinociceptive action of morphine elicited by CCK-8-SO4 can be counteracted by proglumide, a CCK antagonist. The addition of morphine (10(-6)M) to the artificial spinal fluid perfusing the subarachnoidal space of rat spinal cord increases the CCK content of the perfusate. Proglumide can potentiate morphine analgesia without changing the half life of morphine. After seven to eight subcutaneous injections of morphine (4 mg/kg) repeated every two hrs there is tolerance to the antinociceptive action of morphine. Proglumide can partially block or reverse this acute tolerance to morphine.

Animals↗
PubMed1984

Aortic recognition sites for serotonin (5HT) are coupled to phospholipase C and modulate phosphatidylinositol turnover.

The 5HT-mediated contraction of rat thoracic aorta is competitively blocked by the specific receptor antagonist 5HT2 ketanserin. In this tissue the addition of 5HT activated the turnover of 3H-phosphatidylinositol in a ketanserin-reversible fashion. These 5HT2 recognition sites appear to be coupled to a phospholipase C mediated cleavage of phosphatidylinositol.

Animals↗
PubMed1984

Intrinsic GABAergic system of adrenal chromaffin cells.

Histochemical and biochemical studies demonstrate that gamma-aminobutyric acid (GABA), glutamic acid decarboxylase (EC 4.1.1.15), and GABA aminotransferase (EC 2.6.1.19) are present in bovine adrenal chromaffin cells. Moreover, [3H]GABA can be taken up and stored by primary cultures of adrenal chromaffin cells. Nicotinic receptor stimulation or KCl depolarization releases the [3H]GABA taken up by these cell cultures. GABA and benzodiazepine recognition sites located in chromaffin cells interact with each other with modalities similar to those described for GABA and benzodiazepine recognition sites located in synaptic membranes prepared from brain tissue. Bicuculline facilitates the release of catecholamine from chromaffin cells induced by nicotinic receptor stimulation but it fails to influence the release of catecholamine evoked by K+ depolarization. Since the GABA-benzodiazepine receptor system appears to modulate nicotinic receptor function, it is suggested that GABA transmission might participate in modulating responsiveness of chromaffin cells to incoming cholinergic stimuli.

4-Aminobutyrate Transaminase↗
PubMed1984

Inhibition of spontaneous and opiate-modified nociception by an endogenous neuropeptide with Phe-Met-Arg-Phe-NH2-like immunoreactivity.

In rats the antinociceptive actions of morphine (injected intraventricularly) or of [Met5]enkephalin-Arg6-Phe7 (YGGFMRF) (injected intrathecally) were attenuated by a pretreatment with 10 microliter of artificial cerebral spinal fluid containing 1 microM captopril/1 microM bestatin/2.5 microM Phe-Met-Arg-Phe-NH2 (FMRF-NH2) given 5 min earlier by the same route. A high molecular weight form of FMRF-NH2 purified from bovine brain attenuated the antinociceptive action of YGGFMRF. IgG, prepared from a specific FMRF-NH2 antiserum, elicited a moderate antinociception reversible by naloxone; in contrast, IgG prepared from control serum failed to change tail-flick latencies. In rats receiving morphine every 2 hr and anti-FMRF-NH2 IgG every 4 hr, the antinociceptive action was still evident after eight successive injections; in rats receiving only morphine, the antinociceptive action had disappeared after six successive injections. Morphine (1 microM) added to the perfusion fluid of the subarachnoidal spaces of rat spinal cord releases FMRF-NH2-like peptides in the perfusate.

Animals↗
PubMed1984

Behavioral and neurochemical differentiation of specific projections in the septal-hippocampal cholinergic pathway of the rat.

In the rat, an intraseptal injection of the gamma-aminobutyric acid (GABA) agonist muscimol decreases the turnover rate of acetylcholine in the hippocampus and, during extinction of a food-reinforced lever-press response, increases extinction responding in a dose-dependent manner. Intraseptal beta-endorphin decreases the turnover rate of hippocampal acetylcholine through activation of septal GABAergic interneurons and increases extinction responding. On the other hand, intraseptal substance P, which decreases the turnover rate of hippocampal acetylcholine in a manner unrelated to septal GABAergic mechanisms, fails to increase extinction responding. The turnover rate of acetylcholine in various hippocampal regions after intraseptal injection of muscimol and substance P was also studied. Muscimol decreases the acetylcholine turnover rate only in the ventral hippocampus, whereas substance P decreases it only in the dorsal hippocampus. We hypothesize that a lowering in the cholinergic input to the ventral hippocampus is capable of increasing extinction responding, whereas a decrease in the input to the dorsal hippocampus is without such an effect. Hence, the cholinergic projections to the two hippocampal areas are modulated by different transmitter systems and have different physiological functions.

Acetylcholine↗
PubMed1984

Increase in the Bmax of gamma-aminobutyric acid-A recognition sites in brain regions of mice receiving diazepam.

gamma-Aminobutyric acid (GABA) receptors were characterized in vivo by studying ex vivo the binding of [3H]muscimol to cerebellum, cortex, hippocampus, and corpus striatum of mice receiving intravenous injections of tracer doses of high-specific-activity (approximately equal to 30 Ci/mmol) [3H]muscimol. This ligand binds with high affinity (apparent Kd, 2-3 X 10(-9) M) to a single population of binding sites (apparent Bmax, 250-180 fmol per 10 mg of protein). Pharmacological studies using drugs that selectively bind to GABAA or GABAB receptors suggest that [3H]muscimol specifically labels a GABAA recognition site. Moreover, diazepam (1.5 mumol/kg, i.p.) increases the Bmax but fails to change the affinity of [3H]muscimol binding to different brain areas. This diazepam-elicited increase in Bmax is blocked in mice receiving the diazepam antagonist Ro 15-1788 (ethyl-8-fluoro-5,6-dihydro-5-methyl-6-oxo-4H-imidazo[1,5a]-[1,4] benzodiazepine-3-carboxylate). Since the diazepam-induced increase of [3H]muscimol binding is paralleled by a significant potentiation of the inhibitory effect of muscimol on locomotor activity, it is proposed that the facilitatory action on GABAergic transmission elicited in vivo by diazepam is mediated by an increase in the Bmax of the binding sites of GABAA receptors.

Animals↗
PubMed1984

Histamine-containing neurons in the rat hypothalamus.

A specific antiserum against histamine was produced in rabbits, and an immunohistochemical study of histamine-containing cells was carried out in rat brain. The antiserum bound histamine in a standard radioimmunoassay and stained mast cells located in various rat and guinea pig tissues. Enterochromaffin-like cells in the stomach and neurons in the posterior hypothalamic area could be detected with this antiserum. The staining was highly specific and was not abolished by preabsorption with histidine, histidine-containing peptides, serotonin, or catecholamines, whereas preabsorption with histamine completely abolished the staining. Immunoglobulins of this antiserum purified by affinity chromatography stained the same cells as did the crude antiserum, whereas the serum fraction, which was not absorbed by histamine-affinity ligand, failed to stain any neuron. Histamine-immunoreactive neuronal cell bodies were found only in the hypothalamic and premammillary areas of colchicine-treated rats. The largest group of cells was seen in the caudal magnocellular nucleus and medially on the dorsal and ventral aspects of the ventral premammillary nucleus. Immunoreactive nerve fibers, but no cell bodies, were detected in other parts of the brain. Histamine-immunoreactive mast cells were found in the median eminence and pituitary gland. The results suggest that histamine-containing neurons are located only in a small area of the posterior hypothalamus, and these cells are probably the source of ascending and descending fibers detected in other brain areas.

Animals↗
PubMed1984

Further characterization of an enkephalin-generating enzyme from adrenal medullary chromaffin granules.

An adrenomedullary protease capable of generating Met5-enkephalin from endogenous precursor(s) has been purified 1,000-fold using affinity chromatography in combination with gel filtration. This trypsin-like enzyme has an apparent molecular weight of 20,000 daltons by gel filtration. The reactivity of the enzyme toward several fluorogenic peptides, Peptides E and F, and the heptapeptides, Met5-enkephalin-Arg6-Phe7 and Met5-enkephalin-Arg6-Arg7, was examined. The two heptapeptides and the fluorogenic compounds were poor substrates for the adrenal enzyme; in contrast, Peptides E and F were cleaved. The low molecular weight products of Peptide F digestion were identified by HPLC as Arg1-Met6-enkephalin, Met5-enkephalin, and Met5-enkephalin-Lys6, while digestion of Peptide E resulted in the production of Leu5-enkephalin and Met5-enkephalin-Arg6-Arg7. [3H]-beta m-Lipotropin was not hydrolyzed by the adrenal enzyme. These results indicate that this adreno-medullary protease is capable of cleaving adrenal opioid peptides at the paired basic sites and thus represents a possible candidate for a proenkephalin-converting enzyme.

Adrenal Medulla↗
PubMed1984

The muscarinic receptor adenylate cyclase complex of rat striatum: desensitization following chronic inhibition of acetylcholinesterase activity.

Chronic inhibition of acetylcholinesterase activity by treatment with diisopropylfluorophosphate (DFP) decreased the capacity of acetylcholine (ACh) acting at a muscarinic receptor to inhibit basal adenylate cyclase activity in homogenates from rat striatum. There was also a loss of the capacity of ACh to inhibit the activation of adenylate cyclase by dopamine. The desensitization of the muscarinic receptor adenylate cyclase complex was associated with a marked attenuation of the capacity of ACh to stimulate a high-affinity GTPase activity present in striatal membranes. The EC50 value of ACh for inhibiting adenylate cyclase and for stimulating GTPase activity increased following treatment with DFP, while the Hill coefficient for both responses was unaltered.

Acetylcholinesterase↗
PubMed1984

Binding of GRP(14-27) but not bombesin or GRP(1-27) to hypothalamic magnocellular elements: an immunohistochemical study.

Bombesin, gastrin-releasing peptide (1-27), and gastrin-releasing peptide (14-27) abolished the specific immunocytochemical staining revealed by antiserum directed to the C-terminus of gastrin releasing peptide (GRP) and bombesin (BN) in rat hypothalamus. When the antiserum was preabsorbed with GRP(14-27), a strong reaction appeared in hypothalamic magnocellular neurons. This staining of magnocellular elements was produced by lower concentrations of GRP(14-27) than were needed to block immunocytochemical staining revealed by the antiserum in other hypothalamic locations. The distribution of GRP(14-27)-induced immunostaining was similar to that of neurophysin. Since only GRP(14-27) but not GRP(1-27) or bombesin was found to bind to magnocellular cells, it was concluded that binding was due to the N-terminus of GRP(14-27), which resembles the structure of oxytocin and vasopressin. In agreement with this, oxytocin and vasopressin were found to prevent the binding of GRP(14-27) to magnocellular cells. The similarity in localization and the effect of oxytocin and vasopressin suggest that GRP(14-27) may bind to neurophysin at low concentrations. The results suggest that enhancement of staining after preabsorption of antisera with antigens must be interpreted with care. Enhancement can occur at antigen concentrations lower than those required to block the immunostaining. These results fail to support the premise that antigen-induced enhancement of staining is due to antigen binding to specific receptors and subsequent detection of the receptor-bound antigen with the antiserum.

Animals↗
PubMed1984

Action of peptidase inhibitors on methionine5-enkephalin-arginine6-phenylalanine7 (YGGFMRF) and methionine5-enkephalin (YGGFM) metabolism and on electroacupuncture antinociception.

In the spinal cord Met5-enkephalin-Arg6-Phe7 (YGGFMRF) is located in small interneurons of the dorsal and ventral horns. From these storage sites, YGGFMRF can be released by perfusing the subarachnoidal spaces of the spinal cord with artificial spinal fluid containing substance P. In vitro YGGFMRF can be hydrolyzed readily by a dipeptidyl carboxypeptidase. In order to ascertain whether this reaction is physiologically relevant, we measured the content of YGGFMRF and Met5-enkephalin (YGGFM) in subarachnoidal space perfusate in presence and in absence of captopril, bestatin and thiorphan using substance P to activate the release of opioid peptides. Without peptidase inhibitors, the efflux of YGGFMRF and YGGFM was hardly detectable. The addition of captopril to the perfusion medium increased the substance P (10(-7) M)-induced release of YGGFMRF markedly but it increased the efflux of YGGFM to a much smaller extent. When captopril and bestatin were added together the amount of YGGFMRF present in the perfusate was further increased slightly. In contrast, the YGGFM content in the same perfusate was increased greatly by bestatin and only slightly by thiorphan. To characterize the pharmacological profile of these peptidase inhibitors, we compared electroacupuncture antinociception with and without intrathecal injections of captopril and bestatin. This antinociception, as measured by tail-flick latency, was potentiated by the intrathecal injection of captopril and bestatin. These results taken together suggest that YGGFMRF released in the perfusate of the arachnoidal space by substance P is metabolized by both dipeptidyl carboxypeptidase and aminopeptidase.

Acupuncture Therapy↗
PubMed1984

Comparison of iprindole, imipramine and mianserin action on brain serotonergic and beta adrenergic receptors.

Iprindole in vitro displaces mianserin from specific recognition sites (IC50 3 microM). Daily doses (5 mg/kg i.p.) of iprindole repeated for 3 weeks attenuate the norepinephrine stimulation of adenylate cyclase studied in brain slices. Whereas the attenuation of noradrenergic receptor function elicited by imipramine can be antagonized by lesions of serotonergic axons, the inhibition of norepinephrine-induced stimulation of adenylate cyclase elicited by iprindole or mianserin is not inhibited by serotonin axon lesions. Iprindole given daily repeatedly reduces the maximal number of binding sites of [3H]mianserin and [3H]ketanserin; both actions are unchanged by lesions of central serotonergic axons.

Animals↗
PubMed1984

Regulation of the GABA receptor complex by a phosphorylation mechanism.

GABA- modulin , a regulatory component of the GABA/benzodiazepine receptor complex, is phosphorylated by cyclic-AMP-, Ca/calmodulin-, and Ca/phospholipid-dependent protein kinases at distinct sites in the molecule. Phosphorylation of GM by the cyclic-AMP-dependent process results in a complete loss of GM inhibitory activity on specific 3H-GABA binding to synaptic membrane recognition sites. The effect of the Ca2+-dependent phosphorylation, dependent on CaM or PS, of GM is presently unknown but may involve a synergistic or antagonistic action on the cyclic-AMP-dependent phosphorylation. Alternatively, the Ca2+-dependent protein kinases may regulate another function of GM, perhaps its postulated role as a coupler of the GABA/benzodiazepine recognition sites. The results of these experiments strongly implicate a role for protein phosphorylation in the regulation or modulation of GABA receptor function, and such a mechanism may be extrapolated to other neurotransmitter receptor complexes.

Animals↗
PubMed1984

Increase of striatal Met5-enkephalin-Arg6-Phe7 (YGGFMRF) content elicited by long-term treatment with haloperidol.

In rats, daily doses of haloperidol repeated for various time periods increase striatal Met5-enkephalin-Arg6-Phe7 (YGGFMRF) immunoreactivity in a time- and dose-dependent manner. This increase occurred also in other dopamine-rich brain areas. After intraventricular captopril (0.5 mg), the accumulation rate of immunoreactive YGGFMRF was greater in haloperidol- than in saline-injected rats. Intraventricular captopril inhibits the YGGFMRF degradation; hence the greater accumulation rate of YGGFMRF caused by captopril in haloperidol-treated rats suggests that this drug increases the YGGFMRF biosynthesis. A slower rate of YGGFMRF release in haloperidol-treated rats can be excluded as a cause for the drug-induced increase in striatal content of this peptide because the release rates of YGGFMRF elicited by K+ were similar in striatal slices of haloperidol- and saline-treated rats. The similarities between the accumulation rate of immunoreactive YGGFMRF and of Met5-enkephalin induced by haloperidol suggest that haloperidol increases the biosynthesis of the specific messenger RNA for preproenkephalin, an opioid peptide precursor, which contains one copy of YGGFMRF and several copies of Met5-enkephalin.

Animals↗
PubMed1984

Enkephalin biosynthesis in adrenal medulla. Modulation of proenkephalin mRNA content of cultured chromaffin cells by 8-bromo-adenosine 3',5'-monophosphate.

Incubation of primary cultures of chromaffin cells from bovine adrenal medulla with 8-bromo-adenosine 3',5'-monophosphate (8-Br-cyclic AMP) resulted in an increase in proenkephalin mRNA content. The mRNA that increased was detected by hybridization analysis using a cDNA probe and migrated with an apparent size of approximately 1400 bases. The increase in proenkephalin mRNA following 8-Br-cyclic AMP treatment was apparent in 12 hr and continued over 2 days. Corresponding changes were detected in enkephalin-like immunoreactivity but with a 24-hr lag: the cellular content increased significantly after 2 days of treatment and continued to rise over the next 2 days, whereas changes in the amount released to the medium followed the same time course. Dose-response curves for the increase in the content of proenkephalin mRNA and of enkephalin-containing peptides were essentially identical. Chromatographic characterization of the enkephalin-like peptides demonstrated that 8-Br-cyclic AMP increased both the high molecular weight fraction and the low molecular weight fraction, which was shown by high-pressure liquid chromatography to contain Met5-enkephalin, Leu5-enkephalin, and Met5-enkephalin-Arg6-Phe7. Previous results in chromaffin cells have demonstrated that the synthesis of tyrosine hydroxylase is also regulated by cyclic AMP, with a similar time course. These results therefore suggest the possibility of coordinate regulation by cyclic AMP of the expression of the cotransmitters, catecholamines and enkephalin peptides, in the adrenal medulla.

8-Bromo Cyclic Adenosine Monophosphate↗