Summary
The effects of carotid occlusion on the release of catecholamines in the nucleus of the solitary tract (NTS) were investigated in anaesthetized cats. Two aspects of the nucleus (rostral or intermediate NTS) were superfused bilaterally through push-pull cannulae with artificial CSF and the release of the endogenous dopamine, noradrenaline and adrenaline was determined in the superfusate radioenzymatically. The superfusion rate was 150 μl/min or 800 μl/min. In some experiments, superfusion of the intermediate NTS was carried out after denervation of the aortic arch.
In the rostral NTS superfused at a rate of 150 μl/min, bilateral carotid occlusion led to a rise in blood pressure and decreased the release rate of dopamine. These changes continued after occlusion termination. The release rate of noradrenaline was transiently diminished during occlusion. The release of this amine was also decreased after occlusion termination. The release rate of adrenaline was not influenced during carotid occlusion, but it was found to be diminished after termination of the occlusion. Superfusion of the rostral NTS at a rate of 800 μl/min also reduced the release rate of adrenaline after termination of carotid artery occlusion. In the intermediate NTS (superfusion rate 150 μl/min) similar effects of the carotid occlusion on the release rates of dopamine and noradrenaline were observed. In this aspect of the NTS, denervation of the aortic arch abolished the decrease in the noradrenaline release during carotic occlusion, while the release rates of dopamine and adrenaline were decreased during and after termination of the carotid occlusion.
The results suggest that (a) the rise in blood pressure in the carotid sinus after termination of a carotid occlusion decreases the release rates of noradrenaline and adrenaline in the NTS, (b) the decrease in the release of noradrenaline during carotid occlusion is due to impulses originating from the baroreceptors of the aortic arch.
Thus, impulses from carotid sinus and aortic arch modify the release rates of noradrenaline in the NTS so as to counteract blood pressure changes.
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Klausmair, A., Singewald, N. & Philippu, A. Release of endogenous catecholamines in two different regions of the nucleus of the solitary tract as influenced by carotid occlusion. Naunyn-Schmiedeberg's Arch Pharmacol 343, 155–160 (1991). https://doi.org/10.1007/BF00168603
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DOI: https://doi.org/10.1007/BF00168603