Related Experiment Videos
Dorsal premammillary nucleus differentially modulates defensive behaviors induced by different threat stimuli in rats
D Caroline Blanchard1, Chun I Li, David Hubbard
1Pacific Biomedical Research Center, University of Hawaii, Honolulu, HI 96822, USA. blanchar@hawaii.edu
Abstract:
Lesions of the dorsal premammillary nucleus (PMd) have been reported to produce dramatic reductions in responsivity of rats to a live cat. Such lesions provide a means of analyzing the potentially differential neural systems involved in different defensive behaviors, and the relationship between these systems and concepts such as anxiety. Rats with bilateral electrolytic lesions of the PMd were run in an elevated plus maze (EPM), exposed first to cat odor and then to a live cat, and assessed for postshock freezing and locomotion. PMd lesions produced a dramatic reduction in freezing, avoidance, and stretch attend to the cat odor stimulus, and reduction in freezing, with greater activity, and enhanced stretch approach to cat exposure. However, PMd lesions had minimal effects in the EPM, and postshock freezing scores were unchanged. These results confirm earlier findings of reduced defensiveness of PMd-lesioned rats to a cat, extending the pattern of reduced defensiveness to cat odor stimuli as well, but also suggest that such lesions have few effects on nonolfactory threat stimuli.
Insights
Dorsal premammillary nucleus lesions significantly reduce defensive behaviors in rats towards cat stimuli, including odor. However, these lesions minimally impact responses to non-olfactory threats in the elevated plus maze.
Area of Science:
- Neuroscience
- Behavioral Neuroscience
- Animal Behavior
Background:
- The dorsal premammillary nucleus (PMd) is implicated in defensive behaviors.
- Understanding neural systems underlying fear and anxiety is crucial.
- Lesions of the PMd can reveal specific defensive pathways.
Purpose of the Study:
- To investigate the role of the dorsal premammillary nucleus (PMd) in mediating defensive behaviors.
- To determine if PMd lesions affect responses to olfactory (cat odor) and direct (live cat) threat stimuli.
- To assess the impact of PMd lesions on anxiety-like behaviors in the elevated plus maze (EPM).
Main Methods:
- Bilateral electrolytic lesions of the PMd were created in rats.
- Rats were exposed to cat odor and subsequently to a live cat.
- Behavioral responses including freezing, avoidance, locomotion, and stretch attend/approach were assessed.
- Rats were also tested in the elevated plus maze (EPM) and assessed for post-shock freezing.
Main Results:
- PMd lesions significantly reduced freezing, avoidance, and stretch attend behaviors in response to cat odor.
- Lesioned rats showed reduced freezing but increased activity and enhanced stretch approach when exposed to a live cat.
- PMd lesions had minimal effects on behavior in the elevated plus maze and did not alter post-shock freezing.
Conclusions:
- The dorsal premammillary nucleus plays a critical role in mediating defensive responses to predator-related (cat) olfactory and direct stimuli.
- PMd lesions selectively impair responses to specific threat types, suggesting distinct neural circuits for different defensive behaviors.
- These findings contribute to understanding the neural basis of fear, anxiety, and threat detection.