Elsevier

Neuroscience Letters

Volume 345, Issue 3, 24 July 2003, Pages 145-148
Neuroscience Letters

Dorsal premammillary nucleus differentially modulates defensive behaviors induced by different threat stimuli in rats

https://doi.org/10.1016/S0304-3940(03)00415-4Get rights and content

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.

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Acknowledgements

This study was supported by NIH grant 5R25 GM56930-04.

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    The PMd is the focal point of the defense circuit evoked by cat odor exposure in rats [9]. For example, lesions in this area prevent expression of clear defensive behavior in rats exposed to cats or cat odor [11], and bilateral PMd lesions cause a reduction in freezing and avoidance to cat odor [20]. In the current study, the PMd showed a similar activation and attenuation pattern as the approach and activity measures, in that all three measures increased during cat odor exposure and were also attenuated by SB-334867 administration.

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