APStracts 2:0088N, 1995.

CEREBELLAR NITRIC OXIDE IS NECESSARY FOR VESTIBULO-OCULAR REFLEX ADAPTATION, A SENSORI-MOTOR MODEL OF LEARNING. Li, Jun, Sheryl S. Smith, and James G. McElligott. Dept. of Anatomy and Neurobiology, MCP-Hahnemann University, Phila., PA 19102-1192, Dept. of Pharmacology, Temple University School of Medicine, Phila., PA 19140.

APStracts 2:0088N, 1995.

SUMMARY AND CONCLUSIONS
1) Nitric oxide (NO) production in the nervous system has been implicated in cellular mechanisms of learning and memory. Our study investigates an in vivo sensori-motor model of learning. It demonstrates that a localized vestibulo- cerebellar injection of the NO synthase inhibitor, l-N G - monomethyl-arginine (l-NMMA), which specifically blocks NO production, inhibited the acquisition of adaptive vestibulo-ocular reflex (VOR) gain increases but not gain decreases in the goldfish. 2) Restoration of NO production by concomitant administration of l-arginine (the substrate for NO synthase) and l-NMMA, suppressed the inhibitory effect of l-NMMA on adaptive gain increases. 3) This effect of l-NMMA was stereospecific since injection of d-NMMA did not suppress adaptive VOR gain increases. 4) Injection of l-NMMA after VOR adaptation had no effect on retention, failing to alter the post- adaptive recovery after a VOR gain increase. 5) In conclusion, acquisition of adaptive VOR gain increases are affected by cerebellar NO inhibition. However, since gain decreases are not, they may involve either non-NO cerebellar or extra- cerebellar mechanisms. In addition, different processes for acquisition and retention of gain increases may be operating, since inhibition of cerebellar NO affects the acquisition but not the retention phase.

Received 20 March 1994; accepted in final form 14 April 1995.
APS Manuscript Number J182-5.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 25 April 1995.