Pharmacology Biochemistry & Behavior, Vol. 23, pp. 515-518, 1985. ' AnkhoInternational Inc. Printed in the U.S.A. 0091-3057/85$3.00 + .00 Caffeine-Induced Taste Aversion and Mimetic Responses 1 B. C. WHITE AND F. D. MASON Division of Science and Math, Centre College, Danville, KY 40422 Received 22 August 1984 WHITE, B. C. AND F. D. MASON. Caffeine-induced taste aversion and mimetic responses. PHARMACOL BIOCHEM BEHAV 23(4) 515-518, 1985.--Novel tastes preceded a range of caffeine doses (10-80 mg/kg) in a taste aversion training trial. One week later rats which had doses of 30 mg or higher showed strong aversions as measured by a single bottle consumption test. The 10 and 20 mg dose produced the most hyperactivity and apparently enhanced intake of the taste paired with caffeine. During the training trial, rats receiving the 80 mg dose exhibited copious gapes and chin-rubs, mimetic responses to noxious tastes. Gapes also occurred in these subjects during the aversion test. Consumption was more sensitive than mimetic responding as a measure of the aversive effects of caffeine. Only the 80 mg dose produced neophobia. Tests with isotonic injections indicated that tonicity was not the source of the aversions. Caffeine Locomotor activity Mimetic responses Neophobia Taste aversion CAFFEINE, ubiquitous in the contemporary human diet, has now been included in many of the nonprescription weight control medications. The association of caffeine with dieting raises questions about the effects of this methylxanthine on food and water consumption. The use of caffeine in dieting is somewhat paradoxical in light of recent reports that in rats low to moderate doses may increase food consumption [3,10] or leave it unaffected [2]. At doses above 50 mg/kg there are consistent reports of decreased food intake and/ or body weight gain [2, 10, 13]. The results of several of these studies suggest that flavor aversions may be involved in the decrease in food con- sumption and body weight gain. Following forced chronic consumption, rats developed a preference for caffeine but avoided the flavor of the drink in which it had been ingested [12]. A study from our lab [14] found that multiple injections of 60 mg/kg doses produced weight loss and copious displays of chin-rubbing and gaping, mimetic responses associated with noxious tastes [8] and conditioned flavor aversions [4]. In this context we have examined the range of caffeine doses that produce taste aversions, neophobia, mimetic be- haviors and locomotor activity. An additional purpose was to assess the relative sensitivity of consumption and mimetic responding as measures of aversion. EXPERIMENT 1 METHOD Animals Thirty female Long-Evans rats (191-293 g) were ran- domly assigned to five equal groups and housed individually in stainless-steel cages. During the 16 days prior to training, subjects were habituated to a restricted water intake schedule and maintained throughout the study at 85-90% of their ad lib body weight. Each group was assigned to either one of four caffeine doses (10, 20, 40, and 80 mg/kg, IP) or a sodium benzoate vehicle control injection (80 mg/kg, IP). The volume of injections was 1.0 ml/kg. Procedure For the last 9 days of the habituation period the animals were placed in the training-test cages for 15 min during which water was available. A graduated glass centrifuge tube (13.0 ml) with rubber stopper and stainless-steel spout was mounted at one end of the rectangular wiremesh cage (20 x 37 x 17 cm). On the day of training the rats were placed in the training-test cages for 30 min with saline (0.15 M) or saccharin (0.1%) solution available for drinking during the first 15 min. Half of each group received the saline drinking solution and the remainder the saccharin. Immediately following removal of the drinking tubes, the animals were injected with their designated dose of caffeine or sodium benzoate. For 15 min after injection an observer, blind to the treatments, recorded locomotor activity (cross- ings) and the mimetic responses of chin-rubbing and gaping [8]. A chin-rub was recorded when the animal lowered its chin to the substrate and moved forward, rubbing the chin on the floor of the cage. A gape was indicated when the mouth was opened wide which fully exposed the incisors. Behavioral observations were made from an adjacent room through a one-way mirror. The 15 min observation interval was selected because mimetic behaviors appeared within minutes of injections in an earlier study [ 14]. The half-time for absorption of a 25 mg/kg oral dose of caffeine has been reported to be on the order of 6 min [ 1]. This would suggest that behavioral effects could occur very rapidly, especially 1Supported in part by a Centre College Faculty Study Grant. 515