Browsing by Author "LAVADOS, M"

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    CARDIOVASCULAR-RESPONSES TO HYPOXIA IN THE SPONTANEOUSLY BREATHING CAT - REFLEXES ORIGINATING FROM CAROTID AND AORTIC BODIES
    (1983) SERANI, A; LAVADOS, M; ZAPATA, P
    The heart rate (fH) and systemic arterial pressure (Pa) responses to transient anoxemic and cytotoxic hypoxia were studied in 18 pentobarbitone-anesthetized, spontaneously breathing cats, by applying N2 tests and i.v. injections of NaCN. Hyperventilation was accompanied by short-latency increases in Pa and fH; they persisted after bilateral vagotomy, sparing the aortic nerves. Acute section of carotid or aortic nerves in different sequences reduced both fH and Pa responses, the contribution of both pairs of nerves being similar. The recording of carotid chemosensory discharges showed transient stimulus-dependent increases in their frequency, to which the ensuing fH and Pa rises were correlated. After sectioning the 4 buffer nerves, hypoxia provoked long-lasting hypotension and bradycardia. Tachycardia was also observed in response to hypoxia in 4 out of 6 chloralose-anesthetized spontaneously breathing cats, the other 2 presenting bradycardia. The direction of these cyanide-induced changes in fH was not modified by bilateral vagotomy. Tachycardia and hypertension in response to hypoxia are not vagally-mediated consequences of hyperventilation.
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    INHIBITION IN CAROTID-BODY CHEMORECEPTORS MEDIATED BY D-2 DOPAMINOCEPTORS - ANTAGONISM BY BENZAMIDES
    (1983) ZAPATA, P; SERANI, A; LAVADOS, M
    Inhibition of chemosensory nerve impulses in the cat is evoked by dopamine (DA) applied to carotid body chemoreceptors. Pharmacological characterization of the dopaminoceptors involved in this action was determined through their blockade with benzamides, selective antagonists of D-2 receptors. Both metoclopramide and sulpiride were effective blockers of DA-induced chemosensory inhibition. Both drugs induced an immmediate increase in the frequency of carotid nerve chemosensory impulses, suggesting the presence of previous tonic inhibition of chemoreceptor discharges by endogenous DA release from glomus cells.