Acta physiologica Scandinavica
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Acta Physiol. Scand. · Aug 1986
The dipsogenic effect of intracerebroventricular infusion of hypertonic NaCl in the sheep is mediated mainly by the Na ion.
In order to examine the importance of the chloride ion in the dipsogenic effect of intracerebroventricular (ICV) infusion of hypertonic NaCl, the water intake in response to 30-min ICV infusions of hypertonic solutions of different Na salts (0.25 M NaCl, NaI, NaSCN and 0.125 M Na2S2O3), mannitol (0.5 M) and choline chloride (0.25 M) was studied in the sheep. All solutions of the Na salts caused significant water drinking compared with ICV control infusions of isotonic artificial cerebrospinal fluid (CSF), except Na thiosulphate (Na2S2O3), which was much less effective, even after equilibration of its osmolality with the other sodium solutions by adding mannitol (0.125 M Na2S2O3/0.25 M mannitol). An inconsistent and small intake of water was induced by ICV hypertonic mannitol and choline chloride. It is concluded that the dipsogenic effect of ICV infusion of hypertonic NaCl in the sheep is mainly caused by the increased Na rather than the Cl ion concentration or the hyperosmolality in the extracellular fluid of juxtaventricular brain tissue.
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Acta Physiol. Scand. · Oct 1984
Influence of intravenous saline infusion on the aortic baroreceptor and left atrial B-type receptor activity in dogs.
Influence of i.v. saline infusion on aortic arch pressure, left atrial mean pressure, heart rate, and the time-related characteristics of aortic arch baroreceptor and left atrial B-type receptor activities were studied in 20 beagle dogs. Saline infusion induced tachycardia in 10 dogs and bradycardia in 10. ⋯ The number of left atrial B-type action potentials/heart cycle, the average discharge rate and average burst frequency increased in both HR response groups. We conclude that the duration of baroreceptor burst, baroreceptor average burst frequency and the number of baroreceptor impulses/cardiac cycle are the important parameters eliciting baroreceptor reflex to i.v. saline infusion.
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Acta Physiol. Scand. · Sep 1983
Comparative StudyEffects of antidromic trigeminal nerve stimulation in relation to parasympathetic vasodilation in cat nasal mucosa.
High threshold stimulation of the trigeminal nerve in sympathectomized cats caused an atropine and hexamethonium resistant vasodilation in the nasal mucosa. Stimulation of efferent parasympathetic neurons to the nose caused a partially atropine sensitive vasodilation which was abolished by hexamethonium. Combined trigeminal and parasympathetic nerve stimulation did not reveal any obvious functional interactions between these two systems. ⋯ Local infusions of capsaicin, known to release substance P from nerve endings, caused a marked longlasting biphasic vasodilation which was atropine and hexamethonium resistant. In conclusion, the present findings illustrate the presence of two vasodilator mechanisms of different nervous origin in the nasal mucosa. The trigeminal response is probably mediated via release of substance P, while the parasympathetic effect seems to be caused by acetylcholine and VIP.