Summary
The posterior area of the hypothalamus of anaesthetized cats was superfused with artificial cerebrospinal fluid through a push-pull cannula. Electrical stimulation with the non-insulated tip of the cannula elicited a rise of the mean arterial blood pressure. Superfusion of the hypothalamic posterior area with tolazoline or piperoxan caused a dose-dependent inhibition of the pressor responses to electrical stimulation. Labelling of the posterior area with 3H-noradrenaline 2 h before the beginning of the superfusion showed that the inhibitory effect of tolazoline on the pressor responses was accompanied by an increased release of total radioactivity and an enhanced per cent release of 3H-noradrenaline, while that of its metabolites was reduced. Superfusion of the nucleus of the solitary tract with clonidine evoked a dose-dependent inhibition of the pressor responses to electrical stimulation of the ipsilateral hypothalamic posterior area. It is concluded that 1. Alpha-adrenoreceptors are present in the posterior hypothalamus and are involved in the blood pressure rise elicited by its electrical stimulation. 2. A feedback mechanism is present in the hypothalamus which regulates the release of noradrenaline and which is mediated by alpha-adrenoreceptors; inhibition of the regulation of the release of noradrenaline by alpha-adrenoreceptors blocking agents leads to an enhanced release of the neuro-transmitter. 3. Activation of the inhibitory pathways of the nucleus of the solitary tract by clonidine diminishes the pressor response to electrical stimulation of the hypothalamic posterior area. 4. Two adrenergic systems localized in different areas of the central nervous system oppose each other in their regulatory effects on arterial blood pressure.
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This work was supported by the Deutsche Forschungsgemeinschaft and the Stiftung Volkswagenwerk.
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Philippu, A., Roensberg, W. & Przuntek, H. Effects of adrenergic drugs on pressor responses to hypothalamic stimulation. Naunyn-Schmiedeberg's Arch. Pharmacol. 278, 373–386 (1973). https://doi.org/10.1007/BF00501481
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DOI: https://doi.org/10.1007/BF00501481