Morphine Subtracts Subcomponents of Haloperidol-Isolated Postural Support Reflexes To Reveal Gradients of Their Integration

Although cataleptic rats do not spontaneously orient, scan, or walk, they will cling, stand, right themselves in the air, and resist being displaced from a stable position (Schallert, Whishaw, De Ryck, & Teitelbaum, 1978). Morphine produces a state of immobility in which all reflexes used for stable static support (e.g., standing, righting, clinging, and bracing) appear to be inhibited (De Ryck, Schallert, & Teitelbaum, 1980). Addition of morphine to haloperidol abolished or reduced those reflexes used to defend against slow postural displacements (e.g., bracing) but left intact those used to protect against fast postural displacements (e.g., righting in the air). However, although intact, these responses to fast postural displacements were completely abolished by labyrinthectomy, showing that they were controlled only by vestibular inputs. During recovery from morphine's effects, the responses to slow postural displacements reemerged, revealing fractional subcomponents. Furthermore, the reorganization of the subcomponents proceeded along specific body gradients; for example, bracing and standing reemerged caudorostrally, while at the same time, righting and clinging reemerged rostrocaudally.