AN IN-VITRO INVESTIGATION OF THE EFFECTS OF THE ACTH MSH(4-9) ANALOG,ORG-2766, ON GUINEA-PIG MEDIAL VESTIBULAR NUCLEUS NEURONS/

Vestibular compensation is a process of CNS plasticity that is correla ted to a return of resting activity in medial vestibular nucleus (MVN) neurons ipsilateral to a peripheral vestibular deafferentation. Syste mic administration of melanocortin peptides accelerates the compensati on process; the ACTH/MSH(4-9) analogue, Org 2766, accelerates this pro cess at smaller doses than ACTH/MSH(4-10). The present study investiga ted the effect of Org 2766 on MVN neurons in vitro using extracellular single-cell recording. Org 2766 was less potent at the neuronal level than ACTH/MSH(4-10). When Org 2766 and ACTH/MSH(4-10) were tested con secutively on the same neuron, the response was often different. Org 2 766 and ACTH/MSH(4-10) may have a different mode and/or site of action .