Intraventricular Administration of Substance P Increases the Dendritic Arborisation

What is it about?

Substance P was infused in the lateral ventricles of twenty Lewis rats for twenty days. On the twentieth day t,he animals were sacrificed and the cerebellar cortex was processed for electron microscopy. The ultrastructural morphometric analysis revealed that the Purkinje cell dendritic arborisation and the number of the synapses between the parallel fibres and the Purkinje: cell dendritic spines were much higher than in control animals. Numerous unattached spines of the secondary and tertiary dendritic branches of the Purkinje cells were also seen in the molecular layer either free or surrounded by astrocytic sheat h. The incrased number of synapses between the Purkinje cell dendrites and the parallel fibres in the animals, which received substance P intraventricularly, in correlation to control animals. supports a neurotrophine-like activity of the substance P in the mammalian cerebellum, enforcing the pre-programmed capability of the Purkinje cells to develop new synaptic surfaces.

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Why is it important?

In this study the impressive increase of the synapses between the parallel fibres and the Purkinje cell dendritic spines, following intraventricular administration of substance P, supports the concept that substance P may enforce the pre-programmed capability of the Purkinje cells Yn forming and protruding new dendritic spines, which develop synap:;es with the axonic terminals of the granule cells, which ascent in the molecular layer as parallel fibres. This evidence suggests that substance P may act as a local growth factor in the CNS increasing the dendriltic arborisation and the synaptogenesis of the neuronal circuits in the cerebellar cortex

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