Self-injurious behaviour: a comparison of caffeine and pemoline models in rats

Self-injurious behaviour (SIB) is a debilitating behaviour disorder that can have life-threatening consequences. It is often exhibited in intellectually handicapped and autistic populations, and it has been modeled with pharmacological manipulations in animals. We have characterized the induction of SIB using high doses of caffeine and pemoline in rats. Caffeine only produced very mild SIB in a small proportion of the rats, when administered repeatedly at very high doses (140-185 mg/kg/day). All the caffeine-treated rats showed profound signs of caffeine-toxicity at these doses, and lower doses did not induce any self-injury. On the other hand, pemoline was effective across a range of doses (100-300 mg/kg/day), including doses that did not produce overt signs of toxicity (100-200 mg/kg/day). The topography of the tissue injury sites (tail vs. paws and ventrum) differed between caffeine and pemoline treatments, and across doses of pemoline. The speed of onset, the incidence, and the severity of SIB occurred in a dose-orderly manner across the pemoline doses, and there was substantial individual variability in the induction of SIB when a moderately high dose (200 mg/kg/day) was used. These individual differences in vulnerability to self-injure are reminiscent of the fact that some humans with specific neurobiological disorders express SIB and some individuals with those same disorders do not. Accordingly, the pemoline model of SIB may be useful to investigate the neurobiological basis of factors that contribute to etiology of SIB.