Acute cocaine effects on stereotypy and defense: an ethoexperimental approach

Cocaine administration to laboratory animals may produce locomotor hyperact ivity and stereotypies that include sniffing and rearing, in addition to an xiety-like effects. A time-sampling study of the effects of 3, 10 or 30 mg/ kg cocaine (i.p.) over time following injection indicated early enhancement of locomotion and crouching, with the latter most increased in low- and in termediate-dose cocaine groups, with increased rearing and standing during the second hour of the test period. Additional analyses at 30-60 min post-i njection suggested qualitative changes in rearing, with high dose animals s howing more, but shorter, rears, and a higher frequency of sniffing. The hi gh dose cocaine enhancement of sniffing was strongly associated with rear a nd stand behaviors, but also occurred while the animal was crouching. This pattern of changes, with initial crouching/freezing and locomotion (flight? ), followed by rearing, standing, and sniffing behaviors similar to those s een in risk assessment suggests that cocaine, particularly at high doses, m ay elicit defense. An additional study using only saline or the high (30 mg/kg) dose indicated that cocaine produced more sniffing regardless of the direction from which the air stream entered the test cage (i.e. top or bottom). However, cocain e animals oriented their sniffing behaviors toward the incoming air, with r eliably more sniffs up in cages with the air stream entering from the top, and more sniffs down, when the air stream entered through a wire mesh cage bottom. Controls showed the same pattern, but their sniff orientation diffe rences were not reliable. These results indicate that the sniffing that fol lows acute high dose cocaine administration is appropriately oriented towar d relevant environmental stimuli, a factor disconsonant with the interpreta tion of sniffing as a stereotypical behavior, but one that is in agreement with the view that it may reflect a risk assessment component of the defens e pattern. (C) 1998 Elsevier Science Ltd. All rights reserved.