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 anim als is a formidable but essential requirement toward understanding asc ending sensory transmission under naturally occurring conditions. Chro nic 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 spinocerebel lar tract (DSCT) neuronal activity, in conjunction with behavioral sta te recording and drug microiontophoresis. These implant procedures pro vide up to 6 months of stable recording conditions and, when combined with other techniques, allow individual DSCT neurons to be monitored o ver multiple cycles of sleep and wakefulness, following the induction into and recovery from barbiturate anesthesia and/or during the juxtac ellular microiontophoretic ejection of inhibitory or excitatory amino acid neurotransmitters. The combination of such techniques allows a co mprehensive 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 s uch as active sleep.