Time of day influences the voluntary intake and behavioral response to methamphetamine and food reward

Abstract

The circadian timing system influences a vast array of behavioral responses. Substantial evidence indicates a role for the circadian system in regulating reward processing. Here we explore time of day effects on drug anticipation, locomotor activity, and voluntary methamphetamine (MA) and food intake in animals with ad libitum food access. We compared responses to drug versus a palatable treat during their normal sleep times in early day (zeitgeber time (ZT) 0400) or late day (ZT 1000). In the first study, using a between-subjects design, mice were given daily 1-h access to either peanut butter (PB-Alone) or to a low or high concentration of MA mixed in PB (MA + PB). In study 2, we repeated the experiment using a within-subjects design in which mice could choose between PB-Alone and MA + PB at either ZT 0400 or 1000. In study 3, the effects of MA-alone were investigated by evaluating anticipatory activity preceding exposure to nebulized MA at ZT 0400 vs. ZT 1000. Time of day effects were observed for both drug and palatable treat, such that in the between groups design, animals showed greater intake, anticipatory activity, and post-ingestional activity in the early day. Furthermore, there were differences among mice in the amount of MA ingested but individuals were self-consistent in their daily intake. The results for the within-subjects experiment also revealed robust individual differences in preference for MA + PB or PB-Alone. Interestingly, time of day effects on intake were observed only for the preferred substance. Anticipatory activity preceding administration of MA by nebulization was also greater at ZT 0400 than ZT 1000. Finally, pharmacokinetic response to MA administered intraperitoneally did not vary as a function of time of administration. The results indicate that time of day is an important variable mediating the voluntary intake and behavioral effects of reinforcers.

Sincronização fótica e não fótica dos ritmos circadianos em roedores subterrâneos (Ctenomys aff. knighti) e roedores modelo de laboratório (Mus musculus)

“…S4.2.2). Consistent with Keith et al (2013), the robustness of PAA was phasedependent; all mice fed peanut butter at ZT4 (6 of 6) exhibited PAA, but only 4 out of 7 mice displayed PAA when fed at ZT10. We next tested whether PAA persisted in constant conditions by removing the daily palatable meal.…”

“…Several studies have shown that it is difficult to produce even weak anticipatory activity to scheduled palatable meals in mice (Hsu et al, 2010;van der Vinne et al, 2015). In contrast, Keith et al reported robust anticipatory activity to a daily offering of peanut butter in mice using a training protocol that combined scheduled chow and palatable meal training (Keith et al, 2013). In the current study we established a new simplified protocol (that does not require training) to establish PAA in mice during ad libitum chow access.…”

“…S4.2.1 online; the protocol was slightly modified from Keith et al (2013)). After training, mice were provided with ad libitum chow and given peanut butter (for 1 h) at either ZT4 or ZT10 ( Supplementary Fig.…”

“…Rodents anticipate rewarding stimuli, including scheduled access to water, stimulants, and palatable meals (Ángeles-Castellanos et al, 2008;Hsu et al, 2010;Iijima et al, 2002;Keith et al, 2013;Mendoza et al, 2005;Mistlberger, 1992b;Mistlberger and Rusak, 1987;Mohawk et al, 2013). In the current study, we sought to develop an approach to expose the free-running rhythm of the FEO by providing scheduled access to a highfat/high-sugar palatable meal in the presence of ad libitum chow.…”

Period-independent novel circadian oscillators revealed by timed exercise and palatable meals

“…Rodents anticipate rewarding stimuli, including scheduled access to water, stimulants, and palatable meals 16 17 18 19 20 21 22 23 . In the current study, we sought to develop an approach to expose the free-running rhythm of the FEO by providing scheduled access to a high-fat/high-sugar palatable meal in the presence of ad libitum chow.…”