Pompeiano O, Manzoni D, d'Ascanio P, Andre P
Dipartimento di Fisiologia e Biochimica, Università di Pisa, Italy.
Arch Ital Biol. 1994 Jul;132(3):117-45.
In precollicular decerebrate cats, intermittent sinusoidal roll tilt of the whole animal (at 0.15 Hz, +/- 10 degrees) produced a vestibulospinal reflex (VSR), characterized by an increased EMG activity of the forelimb extensor triceps brachii during side-down and a decreased activity during side-up tilt. This reflex was first tested during and after a 3-h period of sustained animal tilt at the same parameters indicated above. An adaptive increase in gain of the VSR progressively developed in some experiments, but not in others. In a second group of experiments, however, sinusoidal roll tilt of the head (0.15 Hz, +/- 10 degrees) was associated with a synchronous roll tilt of the body (at 0.15 Hz, +/- 12.5 degrees). This additional stimulus led to 2.5 degrees of neck rotation, which was thus out of phase with respect to head rotation. In all these experiments, submitted to a 3-h period of sustained neck-vestibular stimulation, the gain of the VSR tested every 10-15 min consistently increased to reach the maximum at the end of the third hour of stimulation. This adaptive process was followed up to 1 h after stimulation. Microinjection into the hemivermal cortex of the cerebellar anterior lobe of the beta-noradrenergic antagonists propranolol or sotalol (0.25-0.50 microliter at 8 micrograms/microliter saline) produced only slight and short-lasting changes in the basic amplitude of the VSR, but always decreased or prevented the occurrence of the adaptive increase in gain of the VSR during sustained out of phase head-neck rotation. The same agents also suppressed the increase in gain of the VSR which occurred in some experiments during sustained roll tilt of the whole animal (at 0.15 Hz, +/- 10 degrees), leading to selective stimulation of labyrinth receptors. On the other hand, the beta-noradrenergic agonist isoproterenol (0.25 microliters at 8 micrograms/microliters saline) brought to the light the adaptive process in other experiments in which no adaptation occurred during sustained animal rotation. These effects occurred when the sites of injection were located within the zone B of the cerebellar anterior vermis, which projects to the lateral vestibular nucleus. In conclusion, the results indicate that the adaptive changes affecting the gain of the VSR in decerebrate cats are facilitated by the noradrenergic afferent system acting on the cerebellar vermis through beta-adrenoceptors.
在中脑前脑桥切断的去大脑猫中，对整个动物进行间歇性正弦波翻滚倾斜（频率0.15Hz，±10度）会产生前庭脊髓反射（VSR），其特征为在身体朝下倾斜时前肢伸肌肱三头肌的肌电图活动增加，而在身体朝上倾斜时活动减少。该反射首先在上述相同参数的3小时持续动物倾斜期间及之后进行测试。在一些实验中，VSR增益出现适应性增加，但在其他实验中未出现。然而，在第二组实验中，头部的正弦波翻滚倾斜（0.15Hz，±10度）与身体的同步翻滚倾斜（0.15Hz，±12.5度）相关联。这种额外的刺激导致颈部旋转2.5度，因此与头部旋转不同步。在所有这些接受3小时持续颈部前庭刺激的实验中，每10 - 15分钟测试一次的VSR增益持续增加，在刺激的第三小时末达到最大值。这种适应性过程在刺激后持续监测1小时。向小脑前叶的半侧蚓部微注射β - 去甲肾上腺素能拮抗剂普萘洛尔或索他洛尔（8微克/微升生理盐水，0.25 - 0.50微升），只会使VSR的基本幅度产生轻微且短暂的变化，但总是会减少或阻止在持续的不同步头颈部旋转期间VSR增益的适应性增加。相同的药物也抑制了在一些实验中整个动物持续翻滚倾斜（0.15Hz，±10度）期间发生的VSR增益增加，这种倾斜会选择性地刺激迷路感受器。另一方面，β - 去甲肾上腺素能激动剂异丙肾上腺素（8微克/微升生理盐水，0.25微升）在其他一些在持续动物旋转期间未发生适应的实验中揭示了适应性过程。当注射部位位于投射至外侧前庭核的小脑前蚓部B区时，会出现这些效应。总之，结果表明，去大脑猫中影响VSR增益的适应性变化是由通过β - 肾上腺素能受体作用于小脑蚓部的去甲肾上腺素能传入系统所促进的。
