The Hamster as a Model for Human Ingestive Behavior

Excerpt

Hamsters are one of the less common rodent models used for the study of ingestive behavior. These animals can be a valuable tool for investigating certain aspects of human behavior and metabolism that cannot be replicated in rats and mice. This chapter will focus on two of those aspects: (i) the appetitive behaviors of food foraging and hoarding and (ii) stress-induced weight gain.

There are many species of hamsters, but laboratory-based studies on ingestive behavior have been almost exclusively limited to Syrian/Golden hamsters (Mesocricetus auratus) and Siberian/Djungarian hamsters (Phodopus sungorus). In a natural setting, hamster physiology and behavior adjust according to seasonal changes in the environment and photoperiod, with duration of nocturnal melatonin release and activity in the suprachiasmatic nucleus acting as the signal that coordinates changes in physiology and behavior (Bartness et al. 1993). Winter-like short day length suppresses reproductive function, causing gonadal regression in both Syrian and Siberian hamsters. Siberian hamsters also change their coat color from agouti to white, lose body fat, and use temporary, daily torpor to improve energy efficiency in cold environments. Body temperature and metabolic rate are decreased for several hours during the daylight hours to conserve energy that is needed for nocturnal foraging in subzero ambient temperatures (Ruf and Heldmaier 1992; Ruf et al. 1993). The capacity for nonshivering thermogenesis is increased (Heldmaier, Steinlechner, and Rafael 1982) and may facilitate the recovery of normothermia at the end of daily torpor. By contrast, Syrian hamsters housed in short photoperiod days gain body fat (Campbell, Tabor, and Davis 1983; McElroy and Wade 1986) primarily by reducing energy expenditure (Wade 1983). Gonadal involution, change in coat color, inhibition of food intake (Hoffman 1973), changes in body fat mass (Wade and Bartness 1984a; Bartness 1996), and 55% of the change in thermogenic capacity (Heldmaier, Steinlechner, and Rafael 1982) can be replicated in the laboratory by reducing the photoperiod to a short day length.