Kalsner S
Can J Physiol Pharmacol. 1982 May;60(5):737-43. doi: 10.1139/y82-102.
The effects of known agonists and of an antagonist on the stimulation-induced efflux of [3H]noradrenaline from left atria of guinea pigs was assessed. This was done to evaluate the hypothesis of presynaptic beta receptors mediating a positive feedback system. Isoproterenol (1.2 X 10(-8) M) enhanced the efflux of tritium with 50 pulses at all four test frequencies and did so to a similar extent at three of them. Exogenous noradrenaline (1.8 X 10(-6) M) inhibited efflux and isoproterenol was ineffective as an enhancer of efflux in its presence. Propranolol (1 X 10(-7) M) did not reliably increase the inhibitory effect of added noradrenaline on stimulation-induced efflux nor did the antagonist by itself under a variety of test conditions decrease the stimulation-induced efflux of tritium. It is concluded that the synaptic quantities of transmitter do not determine the magnitudes of the effects of exogenous agents on tritium efflux and that positive feedback, for both theoretical and empirical considerations, does not function during neurosecretion.
评估了已知激动剂和拮抗剂对豚鼠左心房刺激诱导的[3H]去甲肾上腺素流出的影响。这样做是为了评估介导正反馈系统的突触前β受体的假说。异丙肾上腺素（1.2×10^(-8) M）在所有四个测试频率下以50个脉冲增强了氚的流出，并且在其中三个频率下增强程度相似。外源性去甲肾上腺素（1.8×10^(-6) M）抑制流出，并且在其存在下异丙肾上腺素作为流出增强剂无效。普萘洛尔（1×10^(-7) M）不能可靠地增加添加的去甲肾上腺素对刺激诱导流出的抑制作用，并且在各种测试条件下拮抗剂本身也不会降低刺激诱导的氚流出。结论是，递质的突触量并不决定外源性药物对氚流出的影响大小，并且出于理论和实验考虑，正反馈在神经分泌过程中不起作用。
