[Transformation of long reticulofugal impulse trains by interneurons monosynaptically linked to the reticulospinal...

Transmission of the reticulofugal activity via the interneurons localized in the ventromedial grey matter of the lumbar region and monosynaptically activated from the reticulospinal fibres was studied in anaesthetized immobilized cats. Interneurons usually generated stationary discharges when reticulospinal pathways were rhythmically stimulated with relatively low frequencies (up to 80-100/s); with further increase of stimulation frequency the discharges became non-stationary (initial high-frequency phase was followed by partial or complete discharge suppression). Maximal firing rate at the initial phase could not exceed 180-230 imp./s. The "transfer function" (the ratio of response frequency to stimulation frequency) reached 0.7-0.8 at low stimulation frequencies and decreased substantially at higher ones. Using mathematical modelling of the excitatory and post-activation inhibitory actions in these neurons, the parameters have been estimated which determine the transfer properties, of the interneuronal population relaying reticulofugal activity.