Browsing by Author "Zapata, P"

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    Acute ventilatory and circulatory reactions evoked by nicotine
    (2002) Fernández, R; Larraín, C; Zapata, P
    Either excitatory or inhibitory cardio-respiratory responses induced by nicotine have been reported. We evaluated the joint and separate contributions of peripheral arterial chemoreceptors and pulmonary vagal afferences to nicotine-induced cardio-respiratory responses in 11 pentobarbitone-anaesthetized cats. Nicotine, given i.v. in doses of from 1 to 200 mug/kg, evoked dose-dependent transient increases in tidal volume (VT) and arterial blood pressure (BP), but the highest doses evoked brief apnoea, immediately followed by intense hyperventilation, as well as discrete early hypotension followed by late hypertension. Bilateral section of the aortic and carotid nerves abolished all hyperventilatory responses to nicotine, giving way to apnoea followed by few cycles of reduced VT and profound hypotension followed by slight hypertension in response to intermediate doses (50-100 mug/kg). Subsequent bilateral vagotomy (BV) suppressed apnoeic and hypotensive responses. In other cats initially subjected to BV, only increases in VT and BP were observed in response to nicotine, effects which were no longer observed after additional carotid and aortic deafferentation. These data suggest that excitatory effects of nicotine on respiration and BP are reflexes evoked by stimulation of peripheral arterial chemoreceptors, while inhibitory effects are also reflex responses but evoked from stimulation of pulmonary vagal afferences. (C) 2002 Elsevier Science B. V. All rights reserved.
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    Dopamine modulates carotid nerve responses induced by acetylcholine on the cat petrosal ganglion in vitro
    (1999) Alcayaga, J; Varas, R; Arroyo, J; Iturriaga, R; Zapata, P
    We have recently reponed that application of acetylcholine (ACh) or nicotine to the petrosal ganglion-the sensory ganglion of the glossopharyngeal nerve-elicits a burst of discharges in the carotid nerve branch, innervating the carotid body and sinus, but not in the glossopharyngeal branch, innervating the tongue and pharynx, Thus, the perikarya of sensory neurons for the carotid bifurcation exhibit selective cholinosensitivity. Since dopamine (DA) modulates carotid nerve chemosensory activity, we searched for the presence of DA sensitivity at the perikarya of these neurons in the cat petrosal ganglion superfused in vitro. Applications of DA in doses of up to 5 mg to the ganglion did not modify the rate of spontaneous discharges in the carotid nerve, However, if DA was applied 30 s before ACh injections, ACh-evoked reactions were modified: low doses of DA enhanced the subsequent responses to ACh, while high doses of DA depressed the responses to ACh. This depressant effect of DA on ACh responses was partially antagonized by adding spiroperone to the superfusate. Our results show that the response to ACh of petrosal ganglion neurons projecting through the carotid nerve is modulated by DA acting on D-2 receptors located in the somata of these neurons. Thus, dopaminergic modulation of cholinosensitivity could be shared also by the membranes of peripheral endings and perikarya of primary sensory neurons involved in arterial chemoreception. (C) 1999 Elsevier Science B.V. All rights reserved.