Nucleus basalis magnocellularis and substantia innominata corticopetal cholinergic lesions attenuate freezing induced by predator odor.

Previous studies have demonstrated that corticopetal cholinergic lesions applied to the nucleus basalis magnocellularis and substantia innominata (NBM/SI) attenuate operant suppression induced by aversive events. However, these lesions have no effect on open-arm behavior in the elevated plus-maze or changes in startle reactivity induced by bright light. This raises the possibility that NBM/SI corticopetal cholinergic lesions alter operant behavior and/or appetitive state, as opposed to the aversive state operant suppression is supposed to index. To address this concern, the authors documented the effect of NBM/SI corticopetal cholinergic lesions on freezing induced by a component of fox feces (2,4,5-trimethylthiazoline [TMT]), a paradigm that does not involve food deprivation or operant performance. TMT presentation induced freezing behavior, and this effect was attenuated by NBM/SI corticopetal cholinergic lesions. Because predator odor presentation, but not presentation of a predator, induces defense behaviors that are sensitive to anxiolytic drugs, the results of the study suggest that NBM/SI corticopetal cholinergic lesions attenuate anxiety-like states.