Search results for "Calcium Channel"
showing 10 items of 204 documents
Multiple actions of glaucine on cyclic nucleotide phosphodiesterases, α1-adrenoceptor and benzothiazepine binding site at the calcium channel
1992
1. In the present study, the properties of glaucine (an aporphine structurally related to papaverine) were compared with those of papaverine, diltiazem, nifedipine and prazosin. The work includes functional studies on rat isolated aorta contracted with noradrenaline, caffeine or KCl, and a determination of the affinity of glaucine at calcium channel binding sites of alpha-adrenoceptors, by use of [3H]-(+)-cis-diltiazem, [3H]-nitrendipine and [3H]-prazosin binding to cerebral cortical membranes. The effects of glaucine on the different molecular forms of cyclic nucleotide phosphodiesterases (PDE) isolated from bovine aorta were also determined. 2. Contraction evoked by noradrenaline (1 micro…
Investigations of the dual contractile/relaxant properties showed by antioquine in rat aorta.
1993
1. In the present study we assessed the activity of antioquine, a bisbenzyltetrahydroisoquinoline alkaloid isolated from Pseudoxandra sclerocarpa, by examining its effects on the contractile activity of rat isolated aorta, specific binding of [3H]-(+)-cis-diltiazem, [3H]-nitrendipine and [3H]-prazosin to cerebral cortical membranes and the different molecular forms of cyclic nucleotide phosphodiesterases (PDE) isolated from bovine aorta. 2. Contractions in rat aorta induced by high concentrations of KCl (80 mM) and noradrenaline (1 microM) were inhibited by antioquine in a concentration-dependent manner (0.1 microM- 300 microM). The alkaloid appeared more potent against KCl-induced contract…
L-type calcium channel activity in human atrial myocytes as influenced by 5-HT.
1993
5-Hydroxytryptamine (10 mumol/l; 5-HT) exerted a positive inotropic effect associated with an increase in the Ca2+ current (ICa) in the human right atrium. For detailed analysis, L-type Ca2+ channel currents were recorded from cell-attached patches using 100 mmol/l Ba2+ as charge carrier. Ca2+ channel activity was identified, first, by burst-like inwardly directed currents and, second, by the appearance of long channel openings promoted by Bay K 8644 (1 mumol/l) upon repetitive depolarizations from -80 to 0 mV. The unitary conductance of the Ca2+ channel amounted to 25.8 pS. During superfusion with 5-HT, ensemble averaged (mean) current was enhanced by about 60%. The increase in mean curren…
Presynaptic effects of anandamide and WIN55,212-2 on glutamatergic nerve endings isolated from rat hippocampus
2006
We examined the effects of the endocannabinoide-anandamide (AEA), the synthetic cannabinoid, WIN55,212-2, and the active phorbol ester, 4-beta-phorbol 12-myristate 13-acetate (4-beta-PMA), on the release of [(3)H]d-Aspartate ([(3)H]d-ASP) from rat hippocampal synaptosomes. Release was evoked with three different stimuli: (1) KCl-induced membrane depolarization, which activates voltage-dependent Ca(2+) channels and causes limited neurotransmitter exocytosis, presumably from ready-releasable vesicles docked in the active zone; (2) exposure to the Ca(2+) ionophore-A23187, which causes more extensive transmitter release, presumably from intracellular reserve vesicles; and (3) K(+) channel block…
Comparative study of the efficacy of olmesartan/amlodipine vs. perindopril/amlodipine in peripheral blood pressure after missed dose in type 2 diabet…
2016
Introduction: Combination therapy is needed to control blood pressure (BP) in a large number of hypertensive patients with diabetes mellitus. Adherence to treatment is a major clinical problem; therefore, the time duration of the antihypertensive action of a drug determines BP control when a dose is skipped. Objectives: The aim was to determine whether the fixed-dose combination of olmesartan/amlodipine provides equal efficacy and safety as the perindopril/amlodipine combination when a drug dose is missed. Methods: In this noninferiority trial with a randomized, double-blind, double-dummy parallel group, controlled design, 260 patients received either olmesartan 20-40 mg/amlodipine 5-10 mg …
Effects of clinical and laboratory variables and of pretreatment with cardiovascular drugs in acute ischaemic stroke: A retrospective chart review fr…
2009
Background: Few studies have examined the role of cardiovascular drugs on acute ischaemic stroke prognosis. Aims: To evaluate the relationship between a favourable outcome in patients with acute ischaemic stroke and specific demographic, clinical and laboratory variables and cardiovascular drug pretreatment. Methods: The 1096 patients enrolled in the GIFA study (who had a main discharge diagnosis of ischaemic stroke) represent the final patient sample used in this analysis. Drugs considered in the analysis included angiotensin converting enzyme (ACE)-inhibitors, angiotensin II receptor blockers, statins, calcium channel blockers, anti-platelet drugs, vitamin K antagonists and heparins. The …
USH3A transcripts encode clarin-1, a four-transmembrane-domain protein with a possible role in sensory synapses.
2002
Usher syndrome type 3 (USH3) is an autosomal recessive disorder characterised by the association of post-lingual progressive hearing loss, progressive visual loss due to retinitis pigmentosa and variable presence of vestibular dysfunction. Because the previously defined transcripts do not account for all USH3 cases, we performed further analysis and revealed the presence of additional exons embedded in longer human and mouse USH3A transcripts and three novel USH3A mutations. Expression of Ush3a transcripts was localised by whole mount in situ hybridisation to cochlear hair cells and spiral ganglion cells. The full length USH3A transcript encodes clarin-1, a four-transmembrane-domain protein…
The endocannabinoid system controls key epileptogenic circuits in the hippocampus.
2006
SummaryBalanced control of neuronal activity is central in maintaining function and viability of neuronal circuits. The endocannabinoid system tightly controls neuronal excitability. Here, we show that endocannabinoids directly target hippocampal glutamatergic neurons to provide protection against acute epileptiform seizures in mice. Functional CB1 cannabinoid receptors are present on glutamatergic terminals of the hippocampal formation, colocalizing with vesicular glutamate transporter 1 (VGluT1). Conditional deletion of the CB1 gene either in cortical glutamatergic neurons or in forebrain GABAergic neurons, as well as virally induced deletion of the CB1 gene in the hippocampus, demonstrat…
Characterization of a Ryanodine Receptor inPeriplaneta Americana
1997
Specific binding sites for the alkaloid ryanodine were characterized in membrane preparations from sarcoplasmatic reticulum of Periplaneta americana skeletal muscle. Binding of [3H]ryanodine was optimal at pH 8 and at CaCl2 concentration of about 300 mumol l-1. The Ca-chelating agents EGTA (100 mumol l-1) and EDTA (100 mumol l-1) abolished 95% and 90% of the [3H]ryanodine binding respectively. Preincubation with Ca2+ (100 mumol l-1) restored the ryanodine binding in presence of up to 300 mumol l-1 EGTA. Radioligand binding experiments showed one class of high affinity binding sites for ryanodine. Determination of rate constants revealed 7.05 x 10(6) l mol-1 min-1 for associating and 3.77 x …
Increased contraction to noradrenaline by vasopressin in human renal arteries
2002
Arginine vasopressin (AVP) not only acts directly on blood vessels through vasopressin V1 receptor stimulation but also may modulate adrenergic-mediated responses in animal experiments. The aim of the present study was to assess whether subpressor concentrations of AVP could contribute to an abnormal adrenergic contractile response of human renal arteries.Renal artery rings were obtained from 27 patients undergoing nephrectomy. The rings were suspended in organ bath chambers for isometric recording of tension.AVP (10(-10) mol/l) and the vasopressin V1 receptor agonist [Phe2, Orn8]-vasotocin (10(-10) mol/l) produced a leftward shift of the concentration-response curve to noradrenaline (half-…