Dorsal spinocerebellar tract neuronal activity in the intact chronic cat

The ability to electrophysiologically identify the axonal projections of lumbar neurons recorded in chronic unanesthetized intact awake animals is a formidable but essential requirement toward understanding ascending sensory transmission under naturally occurring conditions. Chronic immobilization procedures previously introduced by Morales et al. (1981) for intracellular studies of motoneurons are modified and then integrated with procedures for antidromic cellular identification and extracellular recording of upper (or lower) dorsal lumbar spinocerebellar tract (DSCT) neuronal activity, in conjunction with behavioral state recording and drug microiontophoresis. These implant procedures provide up to 6 months of stable recording conditions and, when combined with other techniques, allow individual DSCT neurons to be monitored over multiple cycles of sleep and wakefulness, following the induction into and recovery from barbiturate anesthesia and/or during the juxtacellular microiontophoretic ejection of inhibitory or excitatory amino acid neurotransmitters. The combination of such techniques allows a comprehensive examination of synaptic transmission through the DSCT and other lumbar sensory pathways in the intact normally respiring cat and its modulation during the general anesthetic state. These techniques permit investigations of the supraspinal controls impinging on lumbar sensory tract neurons during wakefulness and other behavioral states such as active sleep.