Pharmacology Biochemistry and Behavior, Vol. 42, pp. 219-227, 1992 0091-3057/92 $5.00 + .oO Printed in the U.S.A. All rights reserved. Copyright 0 1992 Pergamon Press Ltd. Strain-Specific Alterations in Consumption of a Palatable Diet Following Repeated Stressor Exposure JENNA GRIFFITH& NOLA SHANKS’ AND HYMIE ANISMAN* Department of Psychology, Carleton University, Ottawa, Ontario, Canada KlS 5B6 Received 27 November 199 1 GRIFFITHS, J., N. SHANKS AND H. ANISMAN. Strain-specific alterations in consumption of a palatable diet fol- lowing repeated stressor exposure. PHARMACOL BIOCHEM BEHAV 42(2) 219-227, 1992.-Exposure to acute inescap- able shock caused reductions in the consumption of a highly palatable diet. The magnitude and duration of the reduction varied across strains of mice. With repeated exposure to footshock, consumption of the diet returned to baseline levels, although alterations of weight appeared to be more persistent. The course of the adaptation varied across strains of mice; however, the rate of adaptation was unrelated to the extent of the alterations of consumption induced by the acute stressor. When mice were exposed to a series of different stressors, the adaptation progressed less readily, and reductions of diet consumption were apparent in strains that had not shown such an effect following acute stressor application or when repeatedly exposed to a single type of stressor. Data were discussed with respect to the mechanisms that might be operative in subserving stressor-induced anhedonia. Stress Anhedonia Feeding Genetics IN support of the contention that stressors promote or exa- cerbate symptoms of depression, it has been shown that environmental stressors will, among other things, result in an- hedonia (4,25). For instance, exposure to an uncontrollable footshock markedly reduced responding for rewarding brain stimulation when electrodes were positioned in mesocortico- limbic structures, including the prefrontal cortex, nucleus accumbens, and ventral tegmentum (30-33). In contrast, responding for stimulation from nigrostriatal structures was unaffected by stressor exposure (28). Because stressors have more profound effects on mesocorticolimbic than nigrostria- tal dopamine (DA) activity, it was suggested that variations of DA activity contribute to the stressor-provoked behavioral disturbances (4,25). Indeed, it was demonstrated that with repeated stressor application the disruption of self-stimulation responding was attenuated, just as the reductions of DA were minimized (10). Finally, repeated administration of the tricy- clic antidepressant, desmethylimipramine, effectively antago- nized the stressor-induced disturbance of self-stimulation from the nucleus accumbens (26,27,29). Paralleling these findings, it was demonstrated that aver- sive stimulation reduced the consumption of highly palatable diets (6,7,11,23,24). Inasmuch as this effect was observed irre- spective of whether a nutritive or non-nutritive solution was used, it is unlikely that the altered consumption was caused by variations in caloric intake, but instead may have reflected a stressor-provoked anhedonia (11,24). Commensurate with the effects of footshock on responding for brain stimulation, the effects of the stressor on consumption of the palatable diet diminished with repeated exposure to a given stressor (12). However, a marked and persistent reduction in the intake of a palatable substance (saccharin or sucrose) was induced when animals were exposed to a series of different stressors over successive days (14,24). Moreover, this effect, like the alterations in responding for brain stimulation, could be an- tagonized by repeated treatment with clinically effective anti- depressant agents (11,13,23). Although behavioral disturbances are engendered by stres- sors in a wide variety of behavioral paradigms, considerable interindividual variability exists in this respect. While some animals exposed to an uncontrollable stressor subsequently display repeated failures to learn or to perform a particular response, other animals are seemingly unaffected by the treat- ment (5). Likewise, it has been demonstrated that marked interstrain differences exist with respect to the behavioral ef- fects of stressors. However, the development of disturbances in one paradigm does not necessarily assure a disturbance in a second paradigm. For instance, DBA/2J mice exposed to inescapable shock exhibited proficient shuttle escape perfor- mance but displayed deficits in responding for electrical stimu- ’ Present address: Douglas Hospital Research Center, 6875 La Salle Blvd., Montreal, Quebec, Canada H4H lR3. ’ To whom reprint requests should be addressed. 219