Pompeiano O, Van Neerven J, Collewijn H, Van der Steen J
Department of Physiology and Biochemistry, University of Pisa, Italy.
Acta Otolaryngol. 1991;111(2):176-81. doi: 10.3109/00016489109137371.
Noradrenaline (NA) has been implicated as a neuromodulator in plasticity, presumably facilitating adaptive processes. Since the flocculus receives noradrenergic afferents, and ablation of the flocculus interferes with the normal adaptive changes in the VOR gain, experiments were performed to find out whether bilateral injection of monoaminergic substances into the flocculus of rabbits could modify the adaptive changes of the VOR. The visual world surrounding the rabbit was oscillated in opposite direction to the platform on which the rabbit was mounted, which resulted in an adaptive increase in the VOR gain; this adaptation was measured either in light or in darkness. Floccular injection of the beta-agonist isoproterenol did not greatly affect the adaptation of the VOR measured in light. In darkness, however, the increase in gain after injection of isoproterenol was larger than during normal adaptation. The beta-antagonist sotalol reduced the adaptation of the VOR gain significantly in light as well as in darkness. In a control condition without pressure for adaptation (only intermittent testing of the VOR gain over a period of 2.5 h), the gain of the VOR was not significantly affected by similar injections of beta-adrenergic agents. We conclude that the noradrenergic system facilitates the adaptation of the VOR gain to retinal slip in rabbits without affecting the VOR gain directly. At least part of this influence is exerted through beta-receptors located in the cerebellar flocculus.
去甲肾上腺素（NA）被认为是一种参与可塑性调节的神经调质，可能有助于适应性过程。由于绒球接受去甲肾上腺素能传入纤维，且绒球切除会干扰前庭眼反射（VOR）增益的正常适应性变化，因此进行了实验，以探究向兔绒球双侧注射单胺能物质是否能改变VOR的适应性变化。使兔周围的视觉环境与兔所站立的平台作相反方向的摆动，这会导致VOR增益适应性增加；这种适应性在明视觉或暗视觉条件下进行测量。向绒球注射β-激动剂异丙肾上腺素对明视觉条件下测量的VOR适应性影响不大。然而，在暗视觉条件下，注射异丙肾上腺素后的增益增加幅度大于正常适应性过程。β-拮抗剂索他洛尔在明视觉和暗视觉条件下均显著降低了VOR增益的适应性。在没有适应性压力的对照条件下（仅在2.5小时内间歇性测试VOR增益），类似的β-肾上腺素能药物注射对VOR增益没有显著影响。我们得出结论，去甲肾上腺素能系统促进兔VOR增益对视网膜滑动的适应性，而不直接影响VOR增益。这种影响至少部分是通过位于小脑绒球的β受体发挥作用的。
