ABNORMAL BEHAVIORS IN THE STARGAZER RAT ARE MALADAPTIVE, BUT NOT ANXIETY-RELATED

The stargazer rat is an autosomal recessive mutant (homozygous stg/stg ) that displays abnormal behavior, including profound hyperactivity. H eterozygous stg/+ littermates are unaffected (i.e., are nonmutants), a nd display normal spontaneous behaviors. Abnormal spontaneous behavior in the stargazer rats suggest that they may be more responsive than t heir normal littermates to external stimuli and more likely to display anxiety-related behavior in tests of emotionality. To test these hypo theses, the reactive behavior of stargazers and unaffected littermates were compared with regard to their responsiveness to nociceptive stim uli (tail flick test), in the open field test, the elevated plus-maze, and in the swim test of Porsolt. In the open field test, the stargaze rs spent a greater percentage of the observation period in the open ar ea (p < 0.05), and demonstrated a significantly higher level of locomo tor activity (p < 0.05). In the elevated plus maze, stargazers spent a significantly greater percentage of their total time in the open arms (p < 0.05), but the number of open-arm entries as a percentage of tot al entries into either arm was not different among the two groups. The stargazers were unable to complete the Porsolt rest, perhaps owing to their being ineffective swimmers. No differences among the groups wer e observed with the tail flick test. Contrary to the original hypothes is, these data suggest that the mutant rats demonstrated less anxiety- related behavior than their nonmutants siblings in tests of emotionali ty.