Elsevier

Neuroscience

Volume 165, Issue 4, 17 February 2010, Pages 1031-1038
Neuroscience

Behavioural Neuroscience
Research Paper
Behavioral control over shock blocks behavioral and neurochemical effects of later social defeat

https://doi.org/10.1016/j.neuroscience.2009.11.005Get rights and content

Abstract

Experience with behavioral control over tailshock (escapable shock, ES) has been shown to block the behavioral and neurochemical changes produced by later uncontrollable tail shock (inescapable shock, IS). The present experiments tested, in rats, whether the protective effect of control over tailshock extends beyond reducing the behavioral and neurochemical impact of a subsequent tailshock experience to stressors that are quite different. Social defeat (SD) was chosen as the second stress experience because it has few if any cues in common with tailshock. SD produced shuttlebox escape learning deficits (“learned helplessness”) and reduced juvenile social investigation 24 h later, as does IS. IS is notable for inducing a large increase in dorsal raphe nucleus (DRN) serotonergic (5-HT) activity as measured by extracellular levels of 5-HT within the DRN, and SD did so as well. ES occurring 7 days before SD blocked this SD-induced DRN activation, as well as the SD-induced interference with shuttlebox escape and reduction in social investigation. Prior exposure to yoked IS did not reduce the DRN 5-HT activation or later behavioral effects produced by SD, and thus the proactive stress-blunting effects of ES can be attributed to it's controllability. Thus, ES confers a very general protection to the impact of a subsequent stress experience.

Section snippets

Subjects

Male Sprague–Dawley rats (Harlan Laboratories, Indianapolis, IN, USA) weighing 275–350 g, were housed four per cage on a 12 h light/dark cycle (on at 07:00 h and off at 19:00 h). Long Evans retired breeders weighing 600–800 g housed individually, under a similar lighting schedule, were selected as alpha males for SD encounters (see below) if they attacked a Sprague–Dawley rat within the first 5 min of several practice encounters. Experiments were conducted between 9:00 h and 1600 h. All

Behavior during social defeat

Fig. 2 shows the ADI for subjects given either ES, yoked IS, or HC control treatment 7 days earlier, from the social exploration experiment (see below). Clearly, rats that had received IS displayed more defeat behavior relative to attacks than did either ES or HC controls. ES had no effect on defeat behavior relative to controls. ANOVA showed a significant effect of prior stress condition (F2,18=3.874, P=0.0399). Fisher's PLSD post-hoc comparison showed that the IS group differed from the home

Discussion

It is of interest that SD produced the same behavioral consequences as does IS. That is, SD both interfered with shuttlebox escape failure and reduced social investigation 24 h later (Amat et al., 2005). Furthermore, the magnitudes of these behavioral effects were comparable to those typically produced by IS. IS produces dramatic behavioral effects relative to other stressors (e.g., restraint, which does not produce escape deficits or reduced social investigation 24 h later, e.g., Christianson

Conclusion

In summary, the experience of behavioral control over a stressor, here tailshock, seems to alter how the organism responds to subsequent stressors that are quite different and have no obvious stimuli in common. This suggests a protective or blunting effect of control that is more general than has been previously supposed.

Acknowledgments

This study was supported by National Institutes of Health grant MH 50479.

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