Cat Pontine Omnipause Neurons: Direct Inhibitory Connection with Forel's Field Burst Neurons Participating in the Genesis of Vertical Saccades

Abstract

This study investigates synaptic connections of omnipause neurons (OPNs) in the midline pontine tegmentum with vertical medium-lead burst neurons (BNs) in the Forel's field H (FFH), using the microstimulation and spike-triggered averaging techniques in chronically prepared alert cats. OPNs on both sides were antidromically activated by microstimulation at the recording sites of the BNs. Systematic tracking with the stimulating microelectrode revealed indications of profuse axonal branching of OPNs within the BN area. Antidromic spikes of the BNs evoked from the oculomotor nucleus and spike bursts of the BNs associated with saccades were suppressed by OPN area microstimulation. Averaged field potentials in the BN area triggered by spikes of OPNs showed monosynaptic positive waves. These results all but confirm the existence of direct inhibitory synaptic connections of OPNs with the BNs in the FFH. The role of OPNs in the genesis of vertical saccades was also discussed.