DA1 AND DA2 RECEPTOR REGULATION IN THE STRIATUM OF YOUNG AND OLD RATSAFTER PERIPHERAL VESTIBULAR LESION

Anatomical, lesion and functional studies have indicated that the meso striatal dopaminergic (DAergic) system may serve as supravestibular ce nter in posture and locomotion control. Nevertheless, no data are avai lable on the involvement of DAergic systems during vestibular compensa tion. This study was designed for the analysis of DA1 and DA2 receptor s in the striatum by means of quantitative receptor autoradiography 28 days after unilateral or bilateral lesion of the labyrinth in 3-month -old rats. Considering the severe decline of DA content and receptors in striatum and the difference in behavioral recovery after vestibular lesions in old age, we also analyzed 24-month-old, lesioned and unles ioned rats. In young rats, hemilabyrinthectomy caused a bilateral incr ease (20-30%) of DA1 receptors and a two-fold increase of DA2 receptor s. In old rats, we observed a similar modification of DA2 receptors, a nd a 50% increase in DA1 receptors. Bilabyrinthectomy did not modify D A1 receptor density and decreased DA2 receptor density in young animal s, whereas it produced an increase in both DA1 and DA2 in old rats. Th is study provides evidence for the involvement of the DAergic system d uring vestibular compensation. Our results also indicate great biochem ical plasticity of the remaining DA receptors in the striatum of old r ats.