A quantitative study of synaptic reorganization in red nucleus neurons after lesion of the nucleus interpositus of the cat: an electron microscopic study involving intracellular injection of horseradish peroxidase.
A quantitative electron microscopic analysis of the corticorubral projection was performed in the red nucleus (RN) of adult cats to determine morphological correlates of synaptic reorganization that occur following a lesion of the interpositus nucleus (IP). Corticorubral synaptic endings were identified by lesioning the sensorimotor cortex 2-6 days before electrophysiological experiments. Horseradish peroxidase (HRP) was injected into electrophysiologically identified RN neurons. Sagittal sections 100 micrometers thick were cut and reacted by diaminobenzidine. Sections containing HRP-positive neurons were selected and embedded in Epon. In normal cats, degenerating corticorubral terminals in the RN region frequently made contact with dendritic profiles, having small cross-sections, while a few made contact with somatic profiles. Similar results were obtained when degenerating terminals making contact with HRP-filled dendrites were analyzed. In the experimental animals, the cortical lesion was performed more than 8 weeks after lesion of the IP. In these animals, degenerating corticorubral terminals were frequently found on proximal dendrites and somata in RN region and HRP-positive neurons in contrast to the findings in normal cats. The results indicate that new corticorubral synapses were formed on proximal dendrites and somata of RN neurons as a consequence of IP lesions.
D000818:Animals; D002415:Cats; D004594:Electrophysiology; D008854:Microscopy, Electron; D009044:Motor Cortex / Q000502:physiology*; D009434:Neural Pathways / Q000502:physiology; D009473:Neuronal Plasticity; D012012:Red Nucleus / Q000473:pathology / Q000502:physiology*; D012038:Regeneration; D013003:Somatosensory Cortex / Q000502:physiology*; D013569:Synapses / Q000502:physiology