ABSTRACT
To analyse the effect of ageing on the projection of the anterior interposed nucleus to the red nucleus, we injected the retrograde tracer fluorogold in the red nucleus of 3-, 6- and 12-month-old mice. The number of labelled neurones in the anterior interposed nucleus fell by 9% between 3 and 6 months and by another 9% between 6 and 12 months (all P < 0.001). This suggests that loss of neurones from the cerebellar nuclei starts well before old age.
Subject(s)
Afferent Pathways/anatomy & histology , Aging/physiology , Brain Mapping , Cerebellar Nuclei/cytology , Neurons/physiology , Red Nucleus/cytology , Animals , Cerebellar Nuclei/metabolism , Male , Mice , Mice, Inbred C57BL , Nerve Degeneration/metabolism , Neurons/pathology , Red Nucleus/anatomy & histology , Red Nucleus/metabolism , Staining and LabelingABSTRACT
A quantitative evaluation of the types of synaptic contacts from afferent fibres in the paratrigeminal nucleus after partial pulpectomy was compared with that after transection of the inferior alveolar nerve (IAN), using transganglionic degeneration. Degenerating terminals with a marked increase in axoplasmic electron opacity were observed bilaterally in the paratrigeminal nucleus of rats submitted to either partial pulpectomy or IAN transection. The total number of degenerating terminals observed after partial pulpectomy was 53% of that for IAN transection. This suggests a considerable contribution of tooth pulp afferent fibres in the total number of synaptic contacts in the intermediate and caudal parts of the paratrigeminal nucleus. In both the partial pulpectomy and IAN-transected groups, the majority of these synapses formed single asymmetric contacts with intermediate and distal dendritic segments, and accounted for 74% of all classified contacts. The remaining 26% of contacts occurred with proximal dendritic segments, dendritic spines, perikaryon, normal terminals and double post-synaptic elements. There was no statistically significant difference in the number of synaptic contacts for each type of synapse, with the exception of contacts with dendritic spines in the contralateral side, between the partially pulpectomised and IAN-transected groups.
