EFFECTS OF THE GABA AGONISTS BACLOFEN AND THIP ON LONG-TERM COMPENSATION IN HEMILABYRINTHECTOMISED RATS

Horizontal eye movements, elicited by sinusoidal rotation in darkness, were recorded with a magnetic search coil technique in pigmented rats , hemilabyrinthectomised 8-12 weeks before the investigation. Separate gains during rotation towards the lesioned side (LS) and the intact s ide (IS) were calculated by a computer program, demonstrating an asymm etry. Systemic single administration of the GABA, agonist baclofen cau sed a dose-related temporary rebalancing of the compensatory eye movem ents to the LS and the IS. At an optimal dose of 14 mu mol/kg b.wt sym metry was achieved by excitation of eye movements during rotation to t he LS and depression during rotation to the IS. Administration of the GABA(A) agonist THIP did not obviously reduce the asymmetry. It is sug gested that stimulation of GABA(B) receptors modifies the tonic imbala nce between the bilateral vestibular nuclei and/or the central process ing of the input from the peripheral sensory organs. (C) 1998 Elsevier Science B.V. All rights reserved.