Sensitization elicited by directly and indirectly acting dopaminergic agonists: comparison using neural network analysis

The major aim of this work was to compare sensitized responses to amphetami ne with those of apomorphine. This was done using both a univariant analysi s of locomotor activity and a multivariant neural network analysis of five different behaviors. The neural network analysis compares the pattern of be haviors from a treated group to a set of patterns from control conditions a nd estimates the dose of drug in control conditions that best matches the p attern of behaviors of the treated group. Both methods indicated that repea ted administration of 2.0 mg/kg amphetamine but not 0.5 mg/kg amphetamine r esulted in sensitization to the administration of a 0.5 mg/kg amphetamine c hallenge given 10 days following the end of the sensitizing regimen. Both a nalyses indicated sensitization following repeated administration of 5 mg/k g apomorphine. Studies of cross sensitization were done using a neural netw ork analysis that could distinguish patterns of behavior elicited by amphet amine from those elicited by apomorphine. Such studies indicated that apomo rphine elicits an apomorphine-like response in animals sensitized to either apomorphine or amphetamine. In contrast, amphetamine produces an amphetami ne-like response in animals sensitized to amphetamine and an apomorphine-li ke response in animals sensitized to apomorphine. The results indicate that neural network analysis may be a useful tool for analyzing drug effects on patterns of behavior.