The relation of the subthalamic and habenular nuclei to oscillating slow wave activity in the midbrain ventral tegmental area

Abstract

Cats anesthetized with barbiturates exhibit bilaterally synchronous slow wave activity in the ventral tegmental area (VTA) adjacent to the interpeduncular nucleus. This activity slows from 15/sec in lightly anesthetized animals to 8/sec as the depth of anesthesia is increased. Similar activity, phase related to that recorded from VTA, is seen in the lateral habenular, entopeduncular and subthalamic nuclei. Exploration of the brain stem with single pulse stimuli indicates a pathway through the subthalamus which ascends near the entopeduncular nucleus, through ventralis anterior and phases dorsocaudally to the lateral habenular region. It then descends to VTA in or about the habenulo-interpeduncular tract. Lesions along the pathway eliminate VTA evoked responses and slow wave oscillations. Following stimulation of peripheral nerves, a long latency response is recorded bilaterally in VTA, and is abolished by lesions along the pathway just described. Single pulse stimulation of the globus pallidus and entopeduncular nucleus suppresses the slow wave activity for 300 msec or more at all sites from which it has been recorded. Pallidal and entopeduncular stimulation also block responses evoked in VTA by subthalamic and peripheral nerve stimulation, but not those initiated by stimulation of nucleus ventralis anterior or habenula, indicating that the inhibition occurs in the pathway caudal to the level of thalamic nucleus ventralis anterior.