Summary
Rabbits were pithed and their sympathetic outflow was stimulated electrically via the pithing rod. Arterial blood pressure, heart rate, the endogenous plasma noradrenaline level, the plasma 3H-noradrenaline clearance and the noradrenaline release rate (the rate of entry of endogenous noradrenaline into the plasma) were determined. Ethylketocyclazocine 0.1 mg kg−1+0.02 mg kg−1 h−1 and 1 mg kg−1 + 0.2 mg kg−1 h−1 but not 0.01 mg kg−1+ 0.002 mg kg−1 h−1 decreased blood pressure, the endogenous plasma noradrenaline level and the noradrenaline release rate. The effects of ethylketocyclazocine 1 mg kg−1+ 0.2 mg kg−1 h−1 were antagonized by naloxone 1 mg kg−1 + 0.5 mg kg−1 h−1. Given alone, naloxone caused no change. It is concluded that ethylketocyclazocine inhibits action potential-evoked release of noradrenaline from postganglionic sympathetic neurones, and hence can lower blood pressure, by a peripheral effect, possibly mediated by opioid receptors at the terminal axons.
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Ensinger, H., Hedler, L., Schurr, C. et al. Ethylketocyclazocine decreases noradrenaline release and blood pressure in the rabbit at a peripheral opioid receptor. Naunyn-Schmiedeberg's Arch. Pharmacol. 328, 20–23 (1984). https://doi.org/10.1007/BF00496099
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DOI: https://doi.org/10.1007/BF00496099