Vestibulocerebellar and vestibulo-oculomotor relations in the rabbit

The present study is the first to demonstrate with anterograde axonal transport connections from the SV and possibly the group y through the superior cerebellar peduncle and the fim to the oculomotor nuclei in the rabbit. Similar connections from SV andy were traced by Henkel and Martin (1977) in the opossum, by Stanton (1980) in the monkey and by Carpenter and Cowie (1985) in the cat. Other authors did not consider the superior peduncle to be an efferent pathway from these nuclei (Gacek, 1971; Tarlov, 1970). Our observations are in compatible with the conclusions of Highstein and Ito (1971), Highstein (1971, 1973a) and Yamamoto et al. (1978), all in the rabbit, and Hirai and Uchino (1984) in the cat, that the excitatory (presumably anterior canal) neurons from the dorsal SV and group y project through the superior cerebellar peduncle, and that the axons of inhibitory neurons from the SV ascend in the ipsilateral f1m. The experiments were carried out on pigmented Dutch belted rabbits (body weight 1.8 - 2.3 kg). The animals were premedicated with Hypnorm (0.3 ml/kg) and were placed in a David Kopf stereotaxic frame with a Wells rabbit head holder. During the operation general anaesthesia was maintained with a halothane-oxygen mixture (Fluotec Mark II) administered through an endotracheal tube (Portex 3.0). The vestibular nuclei and the cerebellum were reached following exposure of the brainstem through a dorsal approach and an enlargment of the occipital foramen