Pompeiano O
Department of Physiology and Biochemistry, University of Pisa, Italy.
Ann N Y Acad Sci. 1992 May 22;656:519-36. doi: 10.1111/j.1749-6632.1992.tb25233.x.
In addition to mossy fibers and climbing fibers, the cerebellar cortex receives noradrenergic and cholinergic afferents. Since the Purkinje (P) cells of the cerebellar vermis (culmen) respond to roll tilt of the animal with a discharge pattern that is out of phase with respect to that of the related lateral vestibular neurons, thus exerting a facilitatory influence on the gain of the vestibulospinal (VS) reflex, we tested the effects of local microinjection into the anterior vermis of noradrenergic and cholinergic agents on these reflexes. In decerebrate cats, unilateral microinjection in the paramedial zone B of the culmen of 0.25 microliters of small doses of alpha 1-, alpha 2-, and beta-noradrenergic agonists (i.e., metoxamine, clonidine, and isoproterenol, respectively) increased the response gain (in impulses/second per deg) of the EMG response of the ipsilateral and to some extent also of the contralateral triceps brachii to animal tilt (at 0.15 Hz, +/- 10 degrees). On the other hand local injection of the corresponding antagonists (i.e., prazosin, yohimbine, and propranolol) either decreased the gain of the ipsilateral triceps brachii to labyrinth stimulation or else prevented the occurrence of the effects induced by the corresponding agonists. An increase in gain of the VS reflexes was also elicited in other experiments by unilateral microinjection either of the nonselective cholinergic agonist carbachol or of the anticholinesterase eserine sulfate. Thus, the effects could be produced by increasing the naturally present amount of acetylcholine. Further experiments indicated that a bilateral increase in the response gain of the triceps brachii to labyrinth stimulation occurred after microinjection of a selective muscarinic (bethanechol) or nicotinic agonist (nicotine), while just the opposite result was obtained after microinjection of the corresponding muscarinic (scopolamine) and nicotinic (hexamethonium, D-tubocurarine) blockers. The effects of the noradrenergic and cholinergic agonists, which persisted for about two hours after the injection, were site specific and dose dependent. It appears, therefore, that the noradrenergic and cholinergic afferents to the cerebellar vermis intervene in the gain regulation of the VS reflexes, possibly by increasing the amplitude of modulation of the P cells to labyrinth stimulation.
除了苔藓纤维和攀缘纤维外，小脑皮质还接受去甲肾上腺素能和胆碱能传入纤维。由于小脑蚓部（山顶）的浦肯野（P）细胞对动物的翻滚倾斜做出反应，其放电模式与相关外侧前庭神经元的放电模式不同步，从而对前庭脊髓（VS）反射的增益产生促进作用，因此我们测试了向蚓部前部局部微量注射去甲肾上腺素能和胆碱能药物对这些反射的影响。在去大脑猫中，在山顶的内侧旁区B单侧微量注射0.25微升小剂量的α1-、α2-和β-去甲肾上腺素能激动剂（即分别为甲氧明、可乐定和异丙肾上腺素），增加了同侧以及在一定程度上对侧肱三头肌对动物倾斜（0.15赫兹，±10度）的肌电图反应增益（每秒每度的冲动数）。另一方面，局部注射相应的拮抗剂（即哌唑嗪、育亨宾和普萘洛尔）要么降低了同侧肱三头肌对迷路刺激的增益，要么阻止了相应激动剂诱导的效应的发生。在其他实验中，单侧微量注射非选择性胆碱能激动剂卡巴胆碱或抗胆碱酯酶硫酸依色林也引起了VS反射增益的增加。因此，这些效应可能是通过增加内源性乙酰胆碱的量产生的。进一步的实验表明，在微量注射选择性毒蕈碱（氨甲酰甲胆碱）或烟碱激动剂（尼古丁）后，肱三头肌对迷路刺激的反应增益出现双侧增加，而在微量注射相应的毒蕈碱（东莨菪碱）和烟碱（六甲铵、筒箭毒碱）阻滞剂后则得到相反的结果。去甲肾上腺素能和胆碱能激动剂的效应在注射后持续约两小时，具有部位特异性和剂量依赖性。因此，小脑蚓部的去甲肾上腺素能和胆碱能传入纤维可能通过增加P细胞对迷路刺激的调制幅度来干预VS反射的增益调节。
