Engagement in a non-escape (displacement) behavior elicits a selective andlateralized suppression of frontal cortical dopaminergic utilization in stress

Although the preferential activation of the prefrontal cortical (PFC) dopam inergic system is generally observed in stress, limited exceptions to this have been observed. Certain non-escape behaviors have been demonstrated to attenuate physiological indices of stress (e.g., coping or displacement res ponses). One well-characterized non-escape behavior observed in stress is c hewing, or gnawing, of inedible objects. Engagement in this behavior attenu ates stress-related activation of the hypothalamopituitary-adrenal axis, in a variety of species. We examined the degree to which engagement in this n on-escape behavior modulates stressor-induced activation of the PFC dopamin e (DA) system. Rats and mice were exposed to a brightly lit novel environme nt (novelty stress) in the presence or absence of inedible objects. Followi ng novelty exposure, various dopaminergic terminal fields were collected an d dopamine and its major catabolite, DOPAC, were measured using HPLC with e lectrochemical detection. DOPAC/DA ratios were calculated as an index of DA utilization. In some cases serotonin (5-HT) and its major catabolite, 5-HI AA, were also measured. In animals that did not chew, novelty exposure elic ited significant increases in DOPAC/DA levels within PFC, nucleus accumbens (shell and core subdivisions), and striatum (relative to quiet-controls). DOPAC/DA responses were greater in the right PFC than in the left PFC. Anim als that chewed displayed significantly lower DOPAC/DA responses in PFC, bu t not other dopaminergic terminal fields. This effect of chewing was always observed in the right PFC and less consistently in the left PFC. Chewing d id not alter novelty-induced increases in PFC 5-HIAA/5-HT responses. Thus, engagement in this non-escape behavior elicits a neuroanatomically and neur ochemically specific attenuation of the PFC DA response in stress. Given th e pivotal role of the PFC in certain cognitive and affective processes, beh avioral regulation of PFC DA utilization may modulate cognitive and/or affe ctive function in stress. (C) 1999 Wiley-Liss, Inc.