Browsing by Author "Larrain, C."
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- ItemCarotid body chemosensory activity and ventilatory chemoreflexes in cats persist after combined cholinergic-purinergic block(ELSEVIER SCIENCE BV, 2007) Reyes, E. P.; Fernandez, R.; Larrain, C.; Zapata, P.Acetylcholine (ACh) and ATP have been proposed as excitatory co-transmitters operating at synapses between glomus cells and sensory nerve endings of the carotid body (CB). To test such hypothesis, we performed experiments on cats under pentobarbitone anesthesia and breathing spontaneously. Cholinergic and purinergic agonists and antagonists were given into one common carotid artery. Chemoreflex ventilatory changes initiated from the ipsilateral CB or chemosensory activity from the ipsilateral carotid nerve were recorded. Agonists ACh, nicotine, epibatidine, ATP, beta gamma-methylene-ATP and gamma S-ATP induced transient chemoreflex enhancements of ventilation or increased chemosensory activity. When given in combination, mecamylamine and suramin suppressed both nicotine- and ATP-induced ventilatory chemoreflexes or chemosensory responses. However, neither chemoreflex hyperventilation induced by brief hypoxic exposures or steady-state hypoxic levels, nor chemosensory excitation elicited by these maneuvers were eliminated. Asphyxia-induced chemosensory excitation was not reduced by combined blockade of ACh and ATP receptors. Furthermore, ventilatory or chemosensory depression evoked by 100% O-2 tests was unmodified, thus evidencing that basal chemosensory drive in normoxia was not suppressed by combined cholinergic-purinergic blockade. Therefore, although ACh and ATP may participate in chemoexcitation of the CB, their involvement fails to explain the origin of chemosensory discharges from synaptic transmission between glomus cells and chemosensory nerve endings of the CB. (c) 2006 Elsevier B.V. All rights reserved.
- ItemEffects of combined cholinergic-purinergic block upon cat carotid body chemoreceptors in vitro(ELSEVIER SCIENCE BV, 2007) Reyes, E. P.; Fernandez, R.; Larrain, C.; Zapata, P.Since acetylcholine (ACh) and ATP have been proposed as excitatory co-transmitters at synapses between glomus cells and sensory nerve endings of the carotid body (CB), we tested such hypothesis by studying the effects of combined cholinergic-purinergic block on the chemosensory activity recorded from cat's carotid bodies perfused and/or superfused in vitro. The preparations were bathed with Tyrode's solution, either normoxic (PO2 = 98.5 +/- 13.5 Torr) or hypoxic (PO2 = 31.8 +/- 5.2 Torr), and the frequency of chemosensory impulses (f(x)) was recorded from the carotid (sinus) nerve. Dose-response curves for f(x) increases evoked by intra-stream boluses of acetylcholine, nicotine and ATP were studied. A combination of mecamylamine 2 mu M and suramin 50 mu M, applied through the perfusate or superfusate, suppressed nicotine- and ATP-induced increases in f(x), but the basal chemosensory activity in normoxia and the chemosensory excitation elicited by hypoxic superfusion were preserved, although variably reduced in most preparations. Thus, in spite of the excitatory effects provoked by applying ACh and ATP to the perfused/superfused CB in vitro, a co-release of these substances cannot account entirely for the chemosensory excitation induced by hypoxic stimulation of the CB. (c) 2006 Elsevier B.V. All rights reserved.
- ItemPlasticity of cardiovascular chemoreflexes after prolonged unilateral carotid body denervation : implications for its therapeutic use(2020) Eugenín, Jaime; Larrain, C.; Zapata, Patricio