ISSN:
1432-1106
Keywords:
Interstitial nucleus of Cajal
;
Head posture
;
Interstitial vestibular interaction
;
Vestibular compensation
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Summary 1. Experiments were performed in cats to determine whether the head tilt following a unilateral lesion of the interstitial nucleus of Cajal (INC) can be attributed to removal of interstitiospihal fibers which have direct excitatory synaptic connections with ipsilateral neck extensor (biventer cervicis-complexus) and flexor (sternocleidomastoid, SCM) motoneurons. Unilateral INC lesions were made either electrolytically or reversibly by procaine infusion into the INC, and electromyographic activity was recorded bilaterally from biventer (BIV), splenius (SP) and SCM muscles. In both groups of lesions, activity of the ipsilateral SP and BIV was higher than that of the contralateral ones. When procaine was infused into the INC of awake cats, an increase of activity of the ipsilateral SP began before the cats presented the typical head tilt to the opposite side. Bilateral INC lesions caused dorsiflexion of the head. These results indicate that the head tilt resulting from unilateral INC lesions can not be explained by simple removal of the ipsilateral, direct excitatory interstitioneck impulses. 2. When unilateral INC lesions were combined with hemilabyrinthectomies, cats that were given labyrinthectomies on the side opposite to the previous INC lesions showed very severe head tilt, whereas cats that received labyrinthectomies on the same side did not show obvious head tilt. Furthermore, it took a much longer time for the cats of the former group to compensate the head tilt than it took those that had single lesions of the INC or labyrinth. These results suggest that the INC and labyrinth interact in the control of head posture and that the INC also plays a role in vestibular compensation. However, when bilatral INC lesions were combined with hemilabyrinthectomies, cats that had previously received bilateral INC lesions and which had fully compensated the head posture recuperated from vestibular symptoms following hemilabyrinthectomy within one to two weeks. Moreover, bilateral INC lesions that were performed in cats which had previously been given hemilabyrinthectomies and in which vestibular symptoms were well compensated did not produce any recurrence of vestibular symptoms. These results indicate that although the INC plays a role in the control of head posture following hemilabyrinthectomy, it is not needed for coarse vestibular compensation.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00236531
