Pair Housing Alters Delay Discounting in Lewis and Fischer 344 Rats

Abstract

Impulsive choice underlies several psychological disorders and can be assessed in laboratory rats using delay-discounting tasks, in which choice is for either one food pellet immediately or three food pellets after a delay. Choice for the smaller, immediate reinforcer is considered the impulsive choice. Lewis (LEW) and Fischer 344 (F344) rats differ in the number of impulsive choices made during this task when singly housed, with LEW choosing the impulsive option more often. Due to increasing recommendations to provide environmental enrichment as a component of animal-husbandry practices, a systematic replication of two previous studies was conducted using pair-housed LEW and F344. Delay discounting was assessed with pair-housed LEW and F344 and compared to previous data from singly housed LEW and F344 collected from the same laboratory. Results showed that differences in impulsive choice between the two strains were attenuated with pair housing. The main result driving this change appears to be an increase in impulsive choice in pair-housed F344 relative to singly housed F344.

Effects of economic context and reward amount on delay and probability discounting

“…These findings are consistent with literature investigating the between‐subjects effects of economic context on delay discounting (Green et al, 1996), suggesting that lower economic context decreases tolerance for delays to reward receipt. Nonhuman animal research investigating the effects of environmental enrichment has also predominantly found that rats reared in enriched contexts display less impulsive choice than their counterparts reared in impoverished environmental contexts (Bardo et al, 2001; Perry et al, 2008; Turturici et al, 2018; Yates et al, 2019). Similarly, these findings are consistent with findings using real‐world data to demonstrate that higher inflation increases within‐subject delay discounting (Ostaszewski et al, 1998).…”

Environmental enrichment promotes adaptive responding during tests of behavioral regulation in male heterogeneous stock rats

“… 15 – 17 ; although these effects may be moderated by genotype e.g. 18 , 19 . Moreover, EE has been shown to exert beneficial effects in animal models of a wide variety of neurodegenerative and neuropsychiatric disorders 20 , 21 , including disorders associated with behavioral dysregulation such as ADHD, autism, schizophrenia, and substance abuse disorder e.g.…”

Probability Discounting of Lewis and Fischer 344 rats: Strain Comparisons at Baseline and Following Acute Administration of d-Amphetamine

“…Specifically, the probability values used during these procedures are usually 100, 75, 50, 25, and PROBABILITY DISCOUNTING OF LEWIS AND FISCHER 344 RATS 37 12.5%, which creates a situation where optimal choice is for the larger, uncertain reinforcer during the 100% and 75% probability blocks, 50% serves as an optimal switchover point, and optimal choice is for the smaller, certain reinforcer during the 25% and 12.5% probability blocks. However, in an attempt to match choice alternatives to those used during delaydiscounting procedures with LEW and F344 (e.g., Anderson & Diller, 2010;Turturici et al, 2018), choice between one and three food pellets was used during the current study. Given that a one-versus-three-pellet procedure was used, probability values were adjusted to account for changes in larger-reinforcer magnitude and were 100, 66.7, 33.3, 16.7, and 8.3%.…”