Taming effects of handling on 6-hydroxydopamine induced ratge.

The purpose of this experiment was to determine the importance of handling to the expression of hyperemotional behaviors, i.e., rage, known to occur after chronic depletion of brain norepinephrine (NE) and dopamine (DA) following central injection of 6-hydroxydopamine (6-OHDA) in rats. Five min of handling per day for 6 consecutive days reduced resistane to capture as well as the magnitude and frequency of startle responding following one 300 mug injection of 6-OHDA intracisternally. Both 6-OHDA-handled and 6-OHDA-unhandled rats showed comparable levels of brain NE, DA, serotonin (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA), comparable resting levels of plasma corticosterone, and comparable adrenal weights. These data demonstrate the importance of handling to the expression of 6-OHDA-induced rage and emphasize the importance of controlling for handling as a variable which can significantly affect the assessment of rage by behavioral criteria in this animal model of hyperemotionality.