Dissociation of anorectic and affective responses to epinephrine and glucose in rats

The purpose of this study was to determine whether the anorexia following epinephrine and glucose IP injections is due to the activation of mechanisms of satiety. Epinephrine (100 micrograms.kg-1) and glucose (4 g.kg-1) were injected IP in rats. In control sessions for epinephrine test, rats received IP saline, and IM epinephrine. In control sessions for the glucose test, rats received IP NaCl, isoosmotic to the glucose solution. Food intake or taste reactivity to a sucrose solution was recorded after these treatments. Epinephrine and glucose decreased food intake by 75% (p < 0.001), and 49% (p < 0.01), compared to their controls. No change of taste reactivity responses was observed with any of these treatments. Twelve-hour fasting did not modify the general taste reactivity responses when compared to the responses evoked in rats fed ad lib. These results might be explained by the fact that anorexia could be obtained by a suppression of hunger without the activation of the mechanisms of satiety. This in turn would imply a possible dissociation between the signals and physiological pathways normally involved in hunger and satiety.