Gaze stabilization in the rabbit : three-dimensional organization and cholinergic floccular control

Whereas a large body of knowledge is available on the rabbit's optokinetic responses about a vertical axis, only fragmentary data have been obtained about horizontal-axis optokinetic responses. With emerging knowledge on the spatial organization of the three dimensional visual messages in the flocculus there is a need for a detailed description of three-dimensional optokinetic responses. We conducted a behavioral study of three-dimensional eye movements, elicited by optokinetic stimulation about horizontal axes, which will be presented in Chapter 2 of this thesis. Chapter 3 descnbes the positive modulatory effects of floccular injection of the cholinergic agonist carbachol and the AChE inhibitor eserine on the OKR and the VOR. A possible mechanism for the positive action of carbachol is proposed in Chapter 4, in the context of a synergistic action between injections of carbachol and the ,8-noradrenergic agonist isoproterenol. Specification of the receptor type involved in the action of carbachol is attempted in Chapter 5. The effects of bilateral and unilateral injections of carbachol on optokinetic nystagmus and afternystagmus are presented in Chapters 6 and 7, whereas Chapter 8 descnbes the effect of bilateral injection of carbachol on vestibular, post-rotatory nystagmus.