Browsing by Author "Valdés, V"

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    Electrophysiological characterization of nicotinic acetylcholine receptors in cat petrosal ganglion neurons in culture
    (2006) Varas, R; Valdés, V; Iturriaga-Vásquez, P; Cassels, BK; Iturriaga, R; Alcayaga, J
    Petrosal ganglion neurons are depolarized and fire action potentials in response to acetylcholine and nicotine. However, little is known about the subtype(s) of nicotinic acetylcholine receptors involved, although alpha 4 and alpha 7 subunits have been identified in petrosal ganglion neurons. Cytisine, an alkaloid unrelated to nicotine, and its bromo derivatives are agonists exhibiting different affinities, potencies and efficacies at nicotinic acetylcholine receptors containing a4 or 0 subunits. To characterize the receptors involved, we studied the effects of these agonists and the nicotinic acetylcholine receptor antagonists hexamethonium and alpha-bungarotoxin in isolated petrosal ganglion neurons. Petrosal ganglia were excised from anesthetized cats and cultured for up to 16 days. Using patch-clamp technique, we recorded whole-cell currents evoked by 5-10 s applications of acetylcholine, cytisine or its bromo derivatives. Agonists and antagonists were applied by gravity from a pipette near the neuron surface. Neurons responded to acetylcholine, cytisine, 3-bromocytisine and 5-bromocytisine with fast inward currents that desensitized during application of the stimuli and were reversibly blocked by 1 mu M hexamethoniurn or 10 nM alpha-bungarotoxin. The order of potency of the agonists was 3-bromocytisine >> acetylcholine congruent to cytisine >> 5-bromocytisine, suggesting that homomeric alpha 7 neuronal nicotinic receptors predominate in cat petrosal ganglion neurons in culture. (c) 2005 Elsevier B.V. All rights reserved.
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    Inhibitory effects of NO on carotid body
    (2003) Valdés, V; Mosqueira, M; Rey, S; Del Rio, R; Iturriaga, R
    We tested the hypothesis that nitric oxide (NO) produced within the carotid body is a tonic inhibitor of chemoreception and determined the contribution of neuronal and endothelial nitric oxide synthase (eNOS) isoforms to the inhibitory NO effect. Accordingly, we studied the effect of NO generated from S-nitroso-N-acetylpenicillamide (SNAP) and compared the effects of the nonselective inhibitor N-omega-nitro-L-arginine methyl ester (L-NAME) and the selective nNOS inhibitor 1-(2-trifluoromethylphenyl)- imidazole (TRIM) on chemosensory dose-response curves induced by nicotine and NaCN and responses to hypoxia (P-O2 approximate to 30 Torr). CBs excised from pentobarbitone-anesthetized cats were perfused in vitro with Tyrode at 38degreesC and pH 7.40, and chemosensory discharges were recorded from the carotid sinus nerve. SNAP (100 muM) reduced the responses to nicotine and NaCN. L-NAME (1 mM) enhanced the responses to nicotine and NaCN by increasing their duration, but TRIM (100 muM) only enhanced the responses to high doses of NaCN. The amplitude of the response to hypoxia was enhanced by L-NAME but not by TRIM. Our results suggest that both isoforms contribute to the NO action, but eNOS being the main source for NO in the cat CB and exerting a tonic effect upon chemoreceptor activity.
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    The efficacy of the lactational amenorrhea method (LAM) among working women
    (2000) Valdés, V; Labbok, MH; Pugin, E; Perez, A
    The purpose of this study was to assess the efficacy of the lactational amenorrhea method (LAM) for family planning among mothers who are separated from their infants by work. The study population, 170 urban middle class women who planned to return to work before 120 days postpartum, were interviewed monthly for 6 months postpartum and contacted at 12 months. The study population received clinical support for expressing their milk and exclusively breast-milk feeding the infants and for the use of LAM for birth spacing. The cumulative life table pregnancy rate by 6-month was 5.2%, with 3 pregnancies, one at each of months 4, 5, and 6. LAM for working women, as described in this article, might be associated with a higher pregnancy risk than LAM use among non-working women. Therefore, women using LAM should be informed that separation from the infant might increase their risk of pregnancy. (C) 2001 Elsevier Science Inc. All rights reserved.