IN-VITRO PHOSPHORYLATION OF MEDIAL VESTIBULAR NUCLEUS AND PREPOSITUS-HYPOGLOSSI PROTEINS DURING BEHAVIORAL RECOVERY FROM UNILATERAL VESTIBULAR DEAFFERENTATION IN THE GUINEA-PIG

Unilateral removal of vestibular nerve input to the vestibular nuclei (e.g. by unilateral labyrinthectomy, UL) results in severe ocular moto r and postural disorders which disappear over time (vestibular compens ation). We investigated whether recovery of ocular motor function is t emporally correlated with changes in protein phosphorylation in the me dial vestibular nucleus (MVN) and prepositus hypoglossi (PH; MVN/PH) i n vitro. Bilateral MVN/PH were dissected from 48 guinea pigs following decapitation at 10 h, 53 h or 2 weeks post-UL, or -sham operation and frozen. Tissue extracts were incubated with [gamma-P-32]ATP +/- Ca2plus phorbol 12,13-dibutyrate and phosphatidylserine. UL resulted in a significant bilateral increase in the P-32-incorporation into a 65-85 kDa band (probably the myristoylated alanine-rich C kinase substrate, MARCKS) in compensated animals (53 h post-UL) under conditions which favoured the activation of protein kinase C. Under identical condition s, the labelling of a 42-49 kDa protein (P46) was increased significan tly in the bilateral MVN/PH between either 10 h or 53 h and 2 weeks po st-UL: there were no significant changes over time in sham controls. T hese results show that later stages of vestibular compensation are acc ompanied by changes in the phosphorylation of several likely protein k inase C substrates in the MVN/PH in vitro. (C) 1997 Elsevier Science B .V.