Pharmacological characterization of presynaptic α2‐autoreceptors in rat submaxillary gland and heart atrium

摘要: 1. The pharmacological properties of presynaptic alpha 2-autoreceptors were studied in rat isolated submaxillary glands and atria. Tissue pieces preincubated with [3H]-noradrenaline, then superfused medium containing desipramine, stimulated electrically. In one series experiments, pEC30 values 12 alpha-adrenoceptor antagonists determined, i.e., negative logarithms concentrations that increased the electrically evoked overflow tritium by 30%. another series, pKD 9 against release-inhibiting effect 5-bromo-6-(2-imidazolin-2-ylamino)-quinoxaline (UK 14304), 3 methoxamine, determined. 2. glands, correlated well their UK 14304 (r = 0.93). same was true for atria 0.92). 3. UK14304 very similar to a maximal difference 0.4. where 0.3. 4. obtained significantly those 0.81). 0.79). However, also indicated consistent differences between two tissues. 5. It is concluded sites action imidazoline (alpha 2-selective), phenylethylamine noradrenaline, methoxamine 1-selective) are exclusively 2-adrenoceptors. There no indication 1-adrenoceptors or an mediated receptors.The 02-autoreceptor population gland differs from atrium.6. Comparison studies literature indicates autoreceptors closely a2D radioligand binding site found bovine pineal probably gland. atrial conform best this site, but agreement more limited; may represent type related to, distinct from, mixture different types.