AJP - Regulatory, Integrative and Comparative Physiology, Vol 259, Issue 3 485-R491, Copyright © 1990 by American Physiological Society
Physiological correlates of schedule-induced activities in rats
G. Mittleman, J. Brener and T. W. Robbins
Department of Experimental Psychology, University of Cambridge, United Kingdom.
Oxygen consumption and heart rate as well as a range of behavior variables
were tracked continuously as rats adapted to a schedule of food delivery.
Over 15 days of observation a majority of the subjects developed
characteristic patterns of schedule-induced polydipsia (SIP) in which bouts
of drinking reliably followed food delivery. Variations in food tray
entries, oxygen consumption, heart rate, and, in the final stage of the
experiment, rates of general activity were also time locked to food
delivery in both rats exhibiting SIP and nondrinkers. However, the patterns
of variation in these measures differed consistently between these two
groups. Oxygen consumption varied over a wider range and reached higher
levels in drinkers than nondrinkers. Additionally, heart rate was lower in
the drinkers, which, in the final stage of the experiment, also exhibited
depressed rates of food tray entries and general activity relative to the
nondrinkers. Each of these between-subject differences was paralleled by
differences within the drinking group between trials on which drinking
occurred and trials on which it did not occur. The implications of these
results on the utility of unidimensional energetic constructs are
discussed.
