POLYAMINE CHANGES IN THE VESTIBULAR NUCLEI OF GUINEA-PIGS FOLLOWING LABYRINTHECTOMY

Vestibular compensation is a process of behavioral recovery from ocula r, motor and postural disorders following unilateral damage to the ves tibular end-organ. Although restoration of the normal resting discharg e rate in the ipsilateral vestibular nuclei is important in compensati on, the biochemical and molecular mechanisms mediating recovery are la rgely unknown. The ornithine decarboxylase polyamine pathway is activa ted in the nervous system following axotomy or denervation. The author s postulate that changes in polyamines mediate vestibular compensation . Within 150-micron brain stem coronal section micropunches analyzed b y high performance liquid chromatography techniques, the polyamine spe rmidine was significantly increased in the ipsilateral lateral vestibu lar nucleus 8 hours following labyrinthectomy in the guinea pig model. Because naturally occurring polyamines modulate excitatory amino acid receptors (N-methyl-D-aspartate [NMDA]) which in turn mediate neurotr ansmission between primary afferents and second order vestibular neuro ns, stimulation of polyamine pathways following neural injury may play a critical role in compensation.