Navegando por Palavras-chave "purinergic neurotransmission"
Agora exibindo 1 - 3 de 3
Resultados por página
Opções de Ordenação
- ItemSomente MetadadadosAlteration of Purinergic Neurotransmission in Isolated Atria of Streptozotocin-induced Diabetic Rats(Lippincott Williams & Wilkins, 2012-02-01) Musial, Diego Castro [UNIFESP]; Galvao, Kleber de Magalhaes [UNIFESP]; Miranda-Ferreira, Regiane [UNIFESP]; Silva Junior, Edilson Dantas da [UNIFESP]; Caricati-Neto, Afonso [UNIFESP]; Jurkiewicz, Neide Hyppolito [UNIFESP]; Jurkiewicz, Aron [UNIFESP]; Broetto Biazon, Ana Carla; Universidade Federal de São Paulo (UNIFESP)Cardiac dysfunctions are described in diabetes. However, the role of purinergic neurotransmission in diabetes-related cardiovascular diseases is unknown. the purpose of this study was to evaluate the purinergic neurotransmission in isolated atria from streptozotocin-induced diabetic rats. the animals were grouped as control and diabetic with 30 days (D30) and 60 days (D60) after streptozotocin-induced diabetes. the isolated left and right atria were used in functional experiments. the effects of adenosine triphosphate, uridine diphosphate, and adenosine were evaluated on atrial inotropism and chronotropism. the antagonists 8-cyclopentyl-1,3-dipropylxanthine and pyridoxal-phosphate-6-azophenyl-2', 4'-disulfonate were also used, as blockers of P-1 and P-2 receptors, respectively. A negative inotropic effect followed by a positive inotropic effect was induced by adenosine triphosphate in isolated atria. This negative inotropic effect was decreased by 25% in left atria of D30. Additionally, the apparent affinity for adenosine was diminished in left atria of D30, suggesting changes in P1 receptor function. No changes were found in the right atria of D30 stimulated by adenosine. the left atria and right atria stimulated by uridine diphosphate showed an increased inotropic effect of 92% and 17%, respectively. No changes were observed in left and right atria of D30 stimulated by uridine diphosphate. Our data showed the involvement of purinergic neurotransmission in diabetes-related cardiovascular changes.
- ItemSomente MetadadadosEnhancement of purinergic neurotransmission by galantamine and other acetylcholinesterase inhibitors in the rat vas deferens(Elsevier B.V., 2004-10-25) Caricati-Neto, A.; D'angelo, LCA; Reuter, H.; Jurkiewicz, N. H.; Garcia, A. G.; Jurkiewicz, A.; Universidade Federal de São Paulo (UNIFESP); Univ Autonoma Madrid; Hosp PrincesaGalantamine, a mild acetylcholinesterase inhibitor and an allosteric ligand of nicotinic receptors, enhanced in a concentration-dependent manner the amplitude of purinergic twitch contractions of the electrically stimulated rat vas deferens (0.2 Hz, 1 ms, 60 V). Other acetylcholinesterase inhibitors also increased the twitches, showing a hierarchy of potencies of galantamine>physostigmine >tacrine>rivastigmine=donepezil. the potentiations seem to be unrelated to the ability to inhibit acetylcholinesterase, since the hierarchy of potencies to block the enzyme in vas deferens was tacrine>physostigmine>rivastigmine>donepezil>galantamine. Acetylcholine also increased the twitches; such effect was produced by a low range of concentrations of acetylcholine (10(-10)-10(-7) M). This facilitatory effect of acetylcholine on twitches was significantly potentiated by galantamine (10(-7)-10(-6) M), but not by rivastigmine or donepezil. A striking enhancement of twitches was also caused by charybdotoxin, a blocker of high-conductance Ca2+-activated K+ channels, and by 4-aminopyridine, a non-specific blocker of K+ channels; in addition, apamin, a blocker of small-conductance Ca2+-activated K+ channels, induced a lower potentiation. the antagonist mecamylamine (10(-7)-10(-6) M) reduced by 80% the potentiation by galantamine, indicating the involvement of nicotinic receptors. Therefore, it is suggested that, besides an inhibition of acetylcholinesterase, some additional mechanisms, such as blockade of Ca2+-dependent K+ channels, or activation of nicotinic receptors of nerve terminals, might be involved in twitch potentiation. These results are relevant in the context of the clinical use of galantamine to improve cognition and behaviour in patients with Alzheimer's disease. (C) 2004 Elsevier B.V. All rights reserved.
- ItemSomente Metadadadosomega-Conotoxins block neurotransmission in the rat vas deferens by binding to different presynaptic sites on the N-type Ca2+ channel(Elsevier B.V., 1997-02-26) Hirata, H.; Albillos, A.; Fernandez, F.; Medrano, J.; Jurkiewicz, A.; Garcia, A. G.; UNIV AUTONOMA MADRID; Universidade Federal de São Paulo (UNIFESP)Electrically-induced twitch responses of the prostatic segment of vas deferens (0.1 Hz, 65 V, 1 ms) are mainly due to the transient presynaptic release of ATP, which acts postsynaptically on non-adrenergic receptors to contract smooth muscle cells. These responses were fully blocked by nanomolar concentrations of the omega-conotoxins GVIA, MVIIA, and MVIIC, most likely by inhibiting Ca2+ entry through presynaptic N-type Ca2+ channels controlling the release of ATP. Repeated washout of the toxins allowed the recovery of contractions, except for omega-conotoxin GVIA, whose inhibitory effects remained unchanged for at least 60 min. in addition, micromolar concentrations of omega-conotoxin MVIIC were unable to protect against the irreversible inhibition of twitch contractions induced by nanomolar concentrations of omega-conotoxin GVIA, At low extracellular Ca2+ concentrations (1.5 mM), 20 nM of omega-conotoxin GVIA or MVIIA inhibited completely the twitch contractions in about 10 min. in 5 mM Ca2+ the blockade of twitch contractions after 10 min was 70% for both toxins. in 1.5 mM Ca2+ omega-conotoxin MVIIC (1 mu M) inhibited completely the twitch contraction after 10 min. in 5 mM Ca2+ blockade developed very slowly and was very poor after 30 min, omega-conotoxin MVIIC depressed the response by only 20%. These results are compatible with the idea that the three omega-conotoxins block the purinergic neurotransmission of the vas deferens by acting on presynaptic N-type voltage-dependent Ca2+ channels. However, omega-conotoxin MVIIC seems to bind to sites different from those recognised by omega-conotoxin GVIA and MVIIA, which are markedly differentiated by their Ca2+ requirements for binding to their receptors.