THE POSTSYNAPTIC DORSAL COLUMN PATHWAY MEDIATES CUTANEOUS NOCICEPTIVE INFORMATION TO CEREBELLAR CLIMBING FIBERS IN THE CAT

1. The location in the spinal cord of the pathway mediating cutaneous nociceptive C fibre input to climbing fibres projecting to the forelimb area of the C3 zone in the cerebellar anterior lobe was investigated in pentobarbitone-anaesthetized cats. Lesions of the spinal cord at the segmental level of C3 sparing the dorsal funiculi (DF preparation) or lesions of the ipsilateral and part of the contralateral dorsal funiculi were made. 2. In the DF preparation, the cutaneous input to climbing fibres projecting to the C3 zone was the same as in cats with an intact spinal cord. Also, the topography of tactile and nociceptive receptive fields and the distribution of A- and C fibre-evoked climbing fibre field potentials was similar to that in cats with an intact spinal cord. 3. In cats with an initially intact spinal cord the cutaneous nociceptive C fibre input and the topographically well organized tactile input to the C3 climbing fibres disappeared following a lesion of the ipsilateral and part of the contralateral dorsal funiculi. Following this lesion the receptive fields of the climbing fibres became indistinct and only irregular responses were evoked on skin stimulation. 4. It is concluded that the cutaneous nociceptive C fibre input from the forelimb to climbing fibres projecting to the C3 zone is mediated by the ipsilateral dorsal funiculus. Since cutaneous C fibres terminate exclusively in the spinal cord close to their entrance zone the postsynaptic dorsal column pathway must be part of this spino-olivocerebellar pathway.