| Abstrakt: |
Rationale: At high doses, methamphetamine produces repetitive stereotypic behaviors, and the degree to which this occurs is heritable. Objectives: Mice of a B6D2F[sub 2] genetic background were selectively bred for four generations for high (HMA) and low (LMA) numbers of stereotyped chewing episodes measured for 1 min at 33 min post-injection following 10 mg/kg methamphetamine (changed to 7 mg/kg for the high line and 15 mg/kg for the low line in the third selected generation to avoid ceiling and floor effects, respectively). We sought to determine whether stereotypic behaviors other than number of repetitive chewing episodes were altered by the selective breeding process. Methods: HMA and LMA mice of the third and fourth selected generations were tested for chewing stereotypy, for a number of other stereotypic behaviors previously observed in rodents, and for several other non-stereotypic responses to methamphetamine. Testing in the third selected generation was conducted by observing behaviors on videotape following 7 mg/kg methamphetamine. In the fourth selected generation, mice were also tested in automated activity monitors following 10 mg/kg methamphetamine and in climbing chimneys following 16 mg/kg methamphetamine. Dose-response curves with doses of 1, 2, 3.5, 7, 10, and 15 mg/kg methamphetamine were constructed for the most commonly observed behaviors. Results: LMA mice, which exhibited low stereotyped chewing, exhibited high stereotyped circling and climbing, and the reverse was true for these behaviors for HMA mice. For most of the other behaviors measured, there were drug effects but no differences between selected lines. Conclusions: These results suggest that these three stereotyped behaviors, chewing, circling, and climbing, at least partly share the same mechanisms, and therefore are influenced by at least some of the same genes, since animals selectively bred for low methamphetamine-induced stereotyped chewing exhibited high amounts of cir... [ABSTRACT FROM AUTHOR] |
