Figure 6

Muscimol and bicuculline have no toxic effect on motoneuron survival in the chicken spinal cord. (A, B) Islet1/2-staining in the lumbar spinal cord of E8 and E10 chicken embryos. Only Islet1/2-positive neurons in the motoneuron pool were counted (circled area). Islet1/2-positive interneurons located in dorsal and medial portions of the spinal cord were not included in our measurements. CC = central canal. (C, D) Number of Islet-positive neurons in the lumbar spinal cord of E8 (C) and E10 (D) chicken embryos in control (vehicle) and following treatment in ovo with bicuculline or muscimol. Bicuculline did not affect the number of Islet-positive neurons at E8 or E10, whereas muscimol causes a significant increase in the number of surviving motoneurons. The number of Islet-positive neurons in the E8 lumbar spinal cord was assessed following in ovo treatments with bicuculline (20 μM/day) or muscimol (5 μM/day) between E5 and E8. The number of Islet-positive neurons at E10 was assessed following in ovo drug treatments between E8 and E10. (E, F) The stimulatory effect of muscimol on motoneuron survival was sustained. Drug-treatment from E5 to E10 (E) or from E5 to E8 (F) resulted in similar number of Islet-positive neurons at E10. *P < 0.05 versus E8 vehicle, **P < 0.05 versus E10 vehicle. NS denotes no significant differences between the groups as indicated by one-way ANOVA.