Spinal interneuronal systems: identification, multifunctional character and reconfigurations in mammals

Abstract

This review focuses on the flexibility of operation of spinal interneuronal networks and their multifunctional character in mammals. It concerns, in particular, two ways in which spinal interneuronal networks may be functionally reorganised, namely by modulating the synaptic actions of primary afferents by monoamines and by GABAergic presynaptic inhibition. The evidence will be reviewed for topographical and target-related differences in modulatory effects in various interneuronal networks and these will be related to differences in the intrinsic properties of different functional types of interneurones in these networks and to the role played by them.

Figure 1. Simplified diagrams of the main reconfigurations of spinal interneuronal networks found in mammals

Circles represent populations of interneurones in pathways to motoneurones (hexagonals); white and grey, excitatory interneurones; black, inhibitory interneurones. Letters indicate sources of input. These are as a rule multiple and are indicated as single, double, or triple only for simplicity. Further explanations are in the text.