J Neurophysiol (December 1, 2002). 10.1152/jn.00499.2002

Submitted on 18 July 2002 Accepted on 16 August 2002

J Neurophysiol 88: 3175-3193, 2002

Responses of Primate Caudal Parabrachial Nucleus and Kölliker-Fuse Nucleus Neurons to Whole Body Rotation

Carey D. Balaban,^1,2,3 David M. McGee,² Jianxun Zhou,³ and Charles A. Scudder^1,2

Departments of ¹Otolaryngology, ²Neurobiology, and ³Communication Sciences and Disorders, University of Pittsburgh, Pittsburgh, Pennsylvania 15213

Surgical procedures
All surgical procedures were conducted under aseptic conditions in an animal surgical suite at the Central Animal Facility of the University of Pittsburgh. Three female macaque monkeys (Macaca nemestrina) were premedicated with atropine (0.05 mg/kg im) and ketamine (12 mg/kg im). After endotracheal intubation, anesthesia was maintained by inhalation of a 1-1.5% halothane-nitrous oxide-oxygen mixture. Three dental acrylic lugs were implanted for secure but painless head stabilization during recording sessions. One lug, positioned centrally on the top of the skull, served as a pedestal for electrical connectors; the other two lugs were positioned behind the ears. At the site of each lug, a 15 × 20-mm patch of skin and periosteum was removed, and small holes were drilled in the skull with a dental burr. Small stainless steel screws were tapped into these holes, and the lug was constructed by applying layers of dental acrylic around the screws to a height of approximately 9 mm.

A "search coil" was implanted on the right eye to measure eye movements, based on the technique of Judge et al. (1980) . The conjunctiva was cut at the limbus, and a preformed 16-mm-diam coil (3 turns of Teflon-insulated stainless steel wire) was sutured to the sclera. Lead wires were passed subcutaneously to a connector on top of the skull. The conjunctiva was sutured with 7-0 vicryl to cover the coil.
A 20-mm-diam, 10-mm-high stainless steel recording chamber was implanted surgically over a hole that was trephined in the parietal bone to permit the chamber to contact the intact dura mater. The chamber was centered at 1 mm left of the midline and +1 to +3.5 mm anterior to the ear bars in different monkeys, angled 15° posteriorly. This approach permitted complete exploration of the left parabrachial nucleus and access to the medial edge of the right parabrachial nucleus. Stainless steel screws were anchored within the surrounding bone through small burr holes, and dental acrylic applied to fix the chamber to the skull. The chamber was filled with "triple antibiotic ointment" and covered with a tightly fitting metal cap.

Recording sessions
Recording sessions began after at least a 2-wk recovery period. The monkeys were seated in a primate chair with their heads fixed to the chair in the stereotaxic plane. They were placed in a two-axis rotation device enclosed in a soundproof, lightproof, and shielded booth. Horizontal rotation about a (vertical) yaw axis was driven by an 80 ft-lb servo-controlled motor (Contraves), which reliably produced waveforms ranging from velocity trapezoids of unlimited duration to sine waves exceeding 10 Hz. The stimulator had an inner axis for producing oscillations in a vertical plane or static deviations up to 90°. With the monkey facing forward, the oscillations were oriented in the pitch plane. Rotating the primate chair 90° in the apparatus allowed oscillations in the roll plane. Intermediate angles produced oscillations in the planes of the vertical semicircular canals.