Equipment

For the rat studies, experiments were conducted in transparent plastic observation chambers (48 × 23 × 20 cm), which resembled the animals’ home cages, except there was no food, water, or bedding in the observation chambers. For the observation of yawning, angled mirrors were placed behind the chambers to facilitate viewing the rat regardless of its position in the chamber. For the mouse experiments, motor activity was assessed in a 21 × 21 × 30 cm³ open field (Omnitech Inc., Columbus, OH), and PPI was tested in San Diego Instruments apparatus (San Diego, CA) as described previously.⁶³ Catalepsy was evaluated in two separate formats; it was assessed with the horizontal bar (6 mm wooden pole, 30 cm long, and 3 cm high) as described,⁶³ and with the 45° inclined screen [the black polyester PetScreen was 16 mesh, 45 × 50 cm in size, and bordered with an aluminum frame (Phifer Inc., Tuscaloosa, Alabama)] assay as outlined elsewhere.⁶⁴