Absence of glucoprivic feeding after stress suggest impairment of noradrenergic neuron function

Feeding in response to 2-deoxy-D-glucose (2DG), a quantifiable behavior which appears to depend on noradrenergic (NE) neuron function, was used in these experiments to evaluate the functional capabilities of NE neurons after stress exposure. Depletion of hypothalamic NE after footshock or hypothermic stress was directly correlated with impairment of glucoprivic feeding. When NE depletion was prevented by prior exposure to chronic stress, no impairment of feeding was observed. After hypothermic stress, repletion of NE proceeded more rapidly in the telencephalon than in the hypothalamus and reappearance of a normal feeding response precisely paralleled the time course of repletion in the hypothalamus. Drinking in response to cell dehydration, a behavior not directly dependent on brain catecholamines, was not impaired after either footshock or hypothermic stress, despite similar NE depletions. Presence of a normal drinking response assured that deficits observed in the 2DG test were not due to nonspecific behavioral suppression resulting from stress. These data suggest that NE neuron function may be impaired or temporarily abolished after severe stress exposure. In addition, these results demonstrate that behavioral pathology need not be the result of massive neurotransmitter depletion but may result from relatively subtle alterations of specific neurotransmitter pools.