Maria Alexandrina Timóteo

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1. Adenosine modulates acetylcholine (ACh) release from the rat motor nerve terminals. Tonic activation of presynaptic A1 inhibitory and/or A2A facilitatory adenosine receptors is regulated by the concentration of the nucleoside at the synapse. The parameters (frequency, duration of pulses, train length) of nerve stimulation determine the amount of(More)
The crosstalk between adenosine and muscarinic autoreceptors regulating evoked [3H]-acetylcholine ([3H]-ACh) release was investigated on rat phrenic nerve-hemidiaphragm preparations. Motor nerve terminals possess facilitatory M1 and inhibitory M2 autoreceptors that can be activated by McN-A-343 (1-30 microm) and oxotremorine (0.3-100 microm), respectively.(More)
BACKGROUND AND PURPOSE The relative contribution of distinct ecto-nucleotidases to the modulation of purinergic signalling may depend on differential tissue distribution and substrate preference. EXPERIMENTAL APPROACH Extracellular ATP catabolism (assessed by high-performance liquid chromatography) and its influence on [(3)H]acetylcholine ([(3)H]ACh)(More)
Nicotinic receptor (nAChR) subtypes involved in preand postjunctional actions underlying tetanic fade were studied in rat phrenic-nerve hemidiaphragms. We investigated the ability of subtype-specific nAChR antagonists to depress nerve-evoked contractions and [H]-acetylcholine ([H]-ACh) release. Muscle tension was transiently increased during brief high(More)
BACKGROUND AND PURPOSE Despite the abundant expression of the UDP-sensitive P2Y6 receptor in urothelial cells and sub-urothelial myofibroblasts its role in the control of bladder function is not well understood. EXPERIMENTAL APPROACH We compared the effects of UDP and of the selective P2Y6 receptor agonist, PSB0474, on bladder urodynamics in anaesthetized(More)
Motor nerve terminals possess multiple voltage-sensitive calcium channels operating acetylcholine (ACh) release. In this study, we investigated whether facilitation of neuromuscular transmission by adenosine generated during neuronal firing was operated by Ca(2+) influx via 'prevalent' P-type or via the recruitment of 'silent' L-type channels. The release(More)
The effect of vasoactive intestinal peptide (VIP) on evoked [(3)H]-acetylcholine ([(3)H]-ACh) release from motor nerve terminals, and its interaction with presynaptic facilitatory A(2A)-adenosine receptors was investigated in the rat phrenic nerve-hemidiaphragms. Facilitation of [(3)H]-ACh release by VIP (100 nM) only becomes apparent when high frequency(More)
In contrast to the well-known signaling role of urothelial ATP to control bladder function, the hypothesis that uracil nucleotides (UTP and/or UDP) also exert autocrine/paracrine actions only recently gained experimental support. Urothelial cells express UDP-sensitive P2Y6 receptors, yet their role in the control of bladder activity has been mostly(More)
Nicotinic receptor (nAChR) subtypes involved in pre- and postjunctional actions underlying tetanic fade were studied in rat phrenic-nerve hemidiaphragms. We investigated the ability of subtype-specific nAChR antagonists to depress nerve-evoked contractions and [(3)H]-acetylcholine ([(3)H]-ACh) release. Muscle tension was transiently increased during brief(More)
In healthy motor endplates, tetanic depression is overcome by tonic adenosine A(2A) -receptor-mediated facilitation of transmitter release. The A(2A) receptor operates a coordinated shift from fast-desensitizing Ca(v) 2.1 (P/Q) calcium influx to long-lasting Ca(V) 1 (L) channels on motor nerve terminals. This study aimed at investigating whether A(2A)(More)