In many mammals, including humans and rats, acute starvation increases locomotor activity. This seemingly paradoxical and potentially lethal behavior pattern may reflect an evolved, multisystem response to sudden threats to metabolic homeostasis. The present study provides a novel test of this idea. Occidental High-(HiS) and Low-(LoS) Saccharin-Consuming rats differ on the taste phenotype and also on some affective measures, on which LoS rats score higher. Wheel running was measured in HiS and LoS rats with food available freely versus for 1 hr daily. As predicted, restricted feeding stimulated significantly more running among LoS rats. Two independent tests of emotionality (acoustic startle, stress-induced analgesia) also distinguished the lines. The confluence of taste, emotion, and reactivity to starvation conditions in species as distantly related as rats and humans points to integrated biobehavioral systems that warrant further exploration.The venerable concepts of metabolic homeostasis and "set point" can be challenged in interesting ways. An example is the excessive exercise that often accompanies reduced food intake in humans and other animals (Epling & Pierce, 1996;Pierce & Epling, 1997; Vincent & Parϑ, 1976). For humans, this pattern is associated with the clinical diagnoses of anorexia and bulimia nervosa (American Psychiatric Association, DSM IV, 1994). Because activity increases in starvation conditions -when conserving energy seems more logical -deprivation-induced hyperactivity (DIH) is sometimes termed "paradoxical" or, in humans, "irrational" and "selfdestructive." Its occurrence in intact, healthy rats, however, implicates phylogenetically old systems, perhaps constituting co-evolved adaptations to famine: Although relocating during a severe food shortage would consume resources and not guarantee survival, it may have, on balance, conferred a selective advantage over remaining in a depleted food patch (Pierce & Epling, 1996).
The differences existing among some european longitudinal growth studies make it necessary to be cautious in the use of standards constructed on different populations. The improvement of the environmental conditions during the last 20 years is probably the most important cause of the "catch-up" phenomenon of the spanish stature. It is probable that racial characteristics also play a role, even in the same country as can be appreciated on comparing two spanish longitudinal studies based on children originary from different regions. All of wich indicates the need to use own standards in those countries wich, like ours, have lived through a period of intenses changes. Even exploratory studies of regional differences in the same country seem necesary.
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