Presented at the International Behavioral Neuroscience Society meeting, Capri, Italy—June 2002

1. INTAKES OF SACCHARIN SOLUTIONS, INCLUDING AN ALCOHOLIC BEVERAGE, AMONG FEMALE RATS TREATED WITH ESTRADIOL VALERATE Meta L Reid,Karen J Boswell, Jessica V Fitch, Brian M GentileandLarry D Reid Laboratory for Psychopharmacology, Siena College, Loudonville, NY andRensselaer Polytechnic Institute, Troy, NY,United States of America SIENA COLLEGE Pharmacological doses of estradiol have dramatic effects on female rats’ self-administration of alcoholic beverages (1) and sweet solutions. With initiation of chronic dosing, intakes of alcoholic beverages are reduced. After chronic dosing, self-administration of alcoholic beverages (both sweetened and unsweetened) are enhanced. Figure 1 summarizes some recently collected data showing the aftereffects of a single dose of estradiol valerate (EV) on intake of a saccharin-sweetened alcoholic beverage. EV is a drug that provides a slow release of estradiol over a period of 2-3 weeks. Notice that the aftereffects of EV enhance appetite for this beverage. Many other kinds of alcoholic beverages are also taken more than ordinarily. Fig. 2. Mean intakes per daily sessions are depicted. B refers to baseline and is a mean across 5 days just before EV. The next 8 data points are means of daily sessions after injections of EV. Notice that rats given saccharin solution dramatically reduced intake whereas those given sucrose solution did not extensively modify their intakes. A question of some interest is why the initially equally acceptable solutions were differentially accepted after injections. Fig. 3. Mean g of intake of saccharin solutions on each day the solutions were presented. One half of the subjects (n = 20) received EV (red markings) and the other half (n = 20) placebos (blue and yellow). Notice injections with EV set into motion a process that leads to an enhanced appetite for the highly acceptable saccharin solution, but a reduced appetite for the less acceptable solution. Further the changes in appetite are enduring, outlasting any direct effects of the single injection of EV. To better understand the apparently complicated effects of EV on appetite for sweet solutions, we assessed the effects of EV on intake of two concentrations of saccharin solution. Method.Forty female Sprague-Dawley rats were housed individually. Half were injected with EV, 2 mg a rat and half with placebo. Five days later and selected days thereafter, half of each group were given one of two saccharin solutions, .25% and 2.00%. Results. Results are summarized in Fig. 3. There is an interaction between hormonal treatment and kind of saccharin solution. This interaction is exemplified by an inspection of the scores of 41-44 days after injections. The mean intake of the low concentration (more palatable) solution across these days for the subjects of EV = 68.4 g compared to 40.2 g for the subjects of placebo, i.e., EV reliably (p = .04) increased intakes. Mean intake of high concentration across these days for EV-subjects = 8.7 g compared to 15.4 g for placebo-subjects, i.e., EV reliably (p = .02) reduced intakes. Discussion. The impetus for assessing intakes of sweet solutions is a better understanding of EV’s effects in modifying intakes of alcoholic beverages. EV modifies intakes of alcoholic beverages and some, but not all sweet solutions, in a similar fashion. Adaptation to and withdrawal from pharmacological doses of estradiol induces a state, an enduring state, manifest as an enhanced appetite for alcoholic beverages and palatable saccharin solutions.The state is also manifest as less acceptance of not so palatable saccharin solutions. In colloquial terms, the state is manifest by both gluttony and finickiness. We are not sure of the implications of those changes for women, but we doubt that such changes are irrelevant to problems of modern women such as an increased incidence of alcoholism and eating disorders. Fig. 1. Intake of a saccharin sweetened (.25%) ethanol (12%) solution. Each data-point represents daily intakes across a week of presentations (24 hr a day). Injections of EV (2 mg/female rat) and placebo were given 15 days before the females’ first chance to take alcoholic beverage. Notice the high levels of intake of the females given placebos. Then, notice the extraordinarily high levels of intake of females given EV. If EV is given to rats that are already taking this beverage, intakes drop dramatically and high levels of intake do not re-establish until some days later. A better understanding of the events leading to the extra ordinary intakes of alcoholic beverage among rats given EV is a focus of this research. Figure 2 is a summary of the direct effects of EV on intake of a saccharin solution (.25%) and a sucrose solution (5%). Notice that intake of the saccharin solution is suppressed by EV whereas intake of the sucrose solution is not. References. 1. Reid et al. 2002, in press, Pharm Biochen Behav contains a more complete discussion of EV and alcohol with relevant references. Presented at the International Behavioral Neuroscience Society meeting, Capri, Italy—June 2002