Effect of catecholamine-receptor stimulating agents on blood pressure after local application in the nucleus tractus solitarii of the medulla oblongata
Abstract
The effect of various catecholamines and alpha-mimetics, given by microinjection in the A2-region of the nucleus tractus solitarii (NTS), on blood pressure was investigated in anesthetized male rats. A dose-dependent decrease of blood pressure and heart rate was induced by adrenaline as the most effective drug, followed by noradrenaline, dopamine, alpha-methylnoradrenaline and octopamine. Ablation of the rostral or caudal part of the NTS, or removal of the area postrema did not diminish the effect of alpha-methylnoradrenaline. Higher doses of noradrenaline and alpha-methylnoradrenaline caused an initial rise of blood pressure, while the blood pressure lowering effect of noradrenaline was diminished, and that of alpha-methylnoradrenaline and dopamine delayed. Isoprenaline and the (+)-stereoisomers of noradrenaline and alpha-methylnoradrenaline were ineffective. The hypotensive effect of dopamine was not prevented by systemic injection of the dopamine beta-hydroxylase inhibitor FLA 63. Prior application of haloperidol, yohimbine and phentolamine antagonized the hypotensive response to dopamine and alpha-methylnoradrenaline. Application of peripherally effective alpha-mimetics into the A2-region had no or little effect, while high...Continue Reading
References
Citations
A study of effects of putative neurotransmitters injected into the lateral cerebral ventricle of man
Cardiovascular effects of noradrenaline microinjected into the insular cortex of unanesthetized rats
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