Decreased circulating leptin and increased neuropeptide Y gene expression are implicated in food deprivation-induced hyperactivity in striped hamsters, Cricetulus barabensis

• Serum leptin levels and behavior were measured in striped hamsters under FD–RF.
• Effects of exogenous leptin on behavior and gene expressions of NPY were examined.
• FD hamsters showed significantly decreased serum leptin and became hyperactive.
• Decreased serum leptin may induce an upregulation of NPY gene expression.
• Exogenous leptin significantly attenuated the increased activity in FD hamsters.

Physiological and behavioral adjustments of small mammals are important strategies in response to variations in food availability. Although numerous of studies have been carried out in rodents, behavioral patterns in response to food deprivation and re-feeding (FD–RF) are still inconsistent. Here we examined effects of a 24 h FD followed by RF on general activity, serum leptin concentrations and gene expression of orexigenic and anorexigenic hypothalamic neuropeptides in striped hamsters (Cricetulus barabensis) with/without leptin supplements. The time spent on activity was increased by 2.5 fold in FD hamsters compared with controls fed ad libitum (P < 0.01). Body mass, fat mass as well as serum leptin concentrations were significantly decreased in FD hamsters in comparison with ad libitum controls, which were in parallel with hyperactivity. During re-feeding, leptin concentrations increased rapidly to pre-deprivation levels by 12 h, but locomotor activity decreased gradually and did not return to pre-deprivation levels until 5 days after re-feeding. Leptin administration to FD hamsters significantly attenuated the increased activity. Gene expression of hypothalamic neuropeptide Y (NPY) was upregulated in FD hamsters and fell down to control levels when hamsters were re-fed ad libitum, similar to that observed in activity behavior. Leptin supplement induced increases in serum leptin concentrations (184.1%, P < 0.05) in FD hamsters and simultaneously attenuated the increase in activity (45.8%, P < 0.05) and NPY gene expression (35%, P < 0.05). This may allow us to draw a more generalized conclusion that decreased leptin concentrations function as a starvation signal in animals under food shortage; to induce an increase in activity levels, leading animals to forage and/or migrate, and consequently increasing the chance of survival. Decreased concentrations of serum leptin in animals subjected to food shortage may induce an upregulation of gene expression of hypothalamus NPY, consequently driving a significant increase in foraging behavior.