Browsing by Author "SERANI, A"

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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.
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    RELATIVE CONTRIBUTION OF CAROTID AND AORTIC BODIES TO CYANIDE-INDUCED VENTILATORY RESPONSES IN THE CAT
    (1981) SERANI, A; ZAPATA, P
    The participation of afferences from carotid and aortic bodies to the hyperventilation caused by cytotoxic hypoxia was assessed in pentobarbitone-anesthetized cats. Dose-response curves for the ventilatory effects induced by i.v. injections of NaCN were obtained before and after successive denervations of peripheral chemoreceptors, in different sequences. Bilateral aortic neurotomy (BAN) or unilateral carotid neurotomy (UCN) did not affect significantly the minimal sensitivity to the drug, although maximal reactivity was reduced in some cats. After bilateral carotid neurotomy (BCN), with preservation of aortic nerves, sensitivity was reduced, but hyperventilation was still provoked by large doses of CN. BAN + BCN abolished the ventilatory responses to the drug. In cats with BAN + UCN, ventilatory responses had a high degree of correlation with increases of carotid chemosensory discharges in the range between 200% of control and the gasping threshold. The aortic bodies of the cat play a significant role in the hyperventilation produced by cytotoxic hypoxia, although it is less marked than that induced through the carotid bodies.