Because of very real practical constraints, conditions in animal shelters are often reminiscent of those in early primate deprivation studies. Dogs are frequently surrendered to shelters because of behavior problems, and aspects of the shelter environment may induce anomalous behavior, increasing the chances that adopted dogs will be returned to the shelters. Comparative psychologists, psychobiologists, and other behavioral scientists possess the knowledge and techniques to help shelters intervene in this cycle. Experience suggests human interaction and the application of basic conditioning procedures can reduce the impact of the shelter environment, and ease the transition into the adoptive home. A program developed to meet these goals is described. Shelters can provide opportunities both for the training of students in animal-related exercises and for limited applied research. Behavioral scientists stand in a unique position to help transform conditions in animal shelters to the benefit of all involved.Approximately 15 million dogs are either turned out as strays or released to animal-welfare agencies by their owners in the United States each year (Moulton, Wright, & Rindy, 1991). These agencies, facing an endless influx of discarded pets, are able to place only a small percentage of homeless dogs (Moulton et al., 1991). Moreover, during their stay in even a modern, well-run shelter, dogs are subject to a variety of psychological stressors, including novelty, isolation from any former attachment figures, exposure to unpredictable and often intense noise, disruption of familiar routines (such as walks for elimination), and a general loss of control over environmental contingencies. These are precisely the types of events known to activate stress-related physiological systems, particularly the hypothalamic-pituitary-adrenal (HPA) axis, in laboratory ani-

Choline-containing diets were chronically fed to male C57BL/6NNIA mice for either 5 or 11 months: from 8-13 months or 13-24 months, respectively. The choline in the chow was supplied in one of three ways: as free choline (choline chloride) or as bound choline as found in a 95% purified preparation of phosphatidylcholine (PC) and in an oil-free granular lecithin formulation (centrolex). The choline in these diets (either free or bound forms) was enriched at low, medium, or high levels (containing 2.4, 4.8, or 10.8 mg/g of chow, respectively). Two low choline diets contained 0.9 and 1.5 mg/g of choline, respectively, but were regarded as choline-adequate since the minimal nutritional requirement for choline is thought to be 0.6 mg/g of chow. All these diets were isocaloric and isonitrogenous. A standard rodent laboratory chow (Purina) contained 2.3 mg/g of choline.One-trial passive-avoidance testing for retention of learning indicated that mice of the C57BL/6NNIA strain show little normal age-related memory loss between 8-24 months old. As such, dietary enrichments did not significantly improve performance in comparison to the mice on the standard lab chow containing abundant choline. Learning was improved, however, in relation to mice on lower choline control diets, by supplementation with choline, PC, or lecithin. Whereas the younger mice tended to respond better at higher levels of enrichment, the older (24 months old) mice showed superior retention of learning following low enrichment levels of PC and lecithin. This suggests that there may be an age-related shift in the optimal, potentially prophylactic, dietary "window."Additional studies are evaluating some parameters reflecting potential membrane changes as a consequence of the various dietary regimens. Analysis of membrane phospholipids in a plasma membrane fraction from mouse forebrain indicated that membrane composition remains remarkably constant; however, diet-modulated enhanced membrane fluidity is suggested by a reduced cholesterol-to-phospholipid ratio in the older mice on low levels of chronic dietary enrichment. Receptor-binding studies from the neocortex (muscarinic, a-and 8-adrenergic), hippocampus (musca-%upported by a grant from Central Soya Company. 469