Circadian Rhythm of Outside-Nest Activity in Wild (WWCPS), Albino and Pigmented Laboratory Rats

Abstract

The domestication process of the laboratory rat has been going on for several hundred generations in stable environmental conditions, which may have affected their physiological and behavioural functions, including their circadian system. Rats tested in our ethological experiments were laboratory-bred wild Norway rats (WWCPS), two strains of pigmented laboratory rats (Brown Norway and Long Evans), and two strains of albino rats (Sprague-Dawley and Wistar). Rats were placed in purpose-built enclosures and their cycle of activity (time spent actively outside the nest) has been studied for one week in standard light conditions and for the next one in round-the-clock darkness. The analysis of circadian pattern of outside-nest activity revealed differences between wild, pigmented laboratory, and albino laboratory strains. During daytime, albino rats showed lower activity than pigmented rats, greater decrease in activity when the light was turned on and greater increase in activity when the light was switched off, than pigmented rats. Moreover albino rats presented higher activity during the night than wild rats. The magnitude of the change in activity between daytime and nighttime was also more pronounced in albino rats. Additionaly, they slept outside the nest more often during the night than during the day. These results can be interpreted in accordance with the proposition that intense light is an aversive stimulus for albino rats, due to lack of pigment in their iris and choroid, which reduces their ability to adapt to light. Pigmented laboratory rats were more active during lights on, not only in comparison to the albino, but also to the wild rats. Since the difference seems to be independent of light intensity, it is likely to be a result of the domestication process. Cosinor analysis revealed a high rhythmicity of circadian cycles in all groups.

Sex differences in juvenile play behavior differ among rat strains

“…Any of these differences in procedure may account for the discrepancies between our results, and other differences between strains may influence how subjects respond in different environments. For example, strain differences have been reported in stress responses (Bielajew et al, ; Konkle et al, ; Tannahill, Dow, Fairhall, Robinson, & Fink, ) and in circadian rhythms (Stryjek, Modlińska, Turlejski, & Pisula, ). Although our previous experiments using Long‐Evans rats tested under red light (otherwise using an almost identical paradigm as the current test with the cage mate) yielded similar results in terms of play duration (36 ± 11 s/30 min), pin frequency (1.7 ± 0.3/30 min), and pin duration (13 ± 4 s/30 min) (Northcutt & Nguyen, ), other strains may be more sensitive to light conditions.…”

Peer Review #1 of "How does agonistic behaviour differ in albino and pigmented fish? (v0.1)"

“…Albino rodents have a poorer sense of smell (Keeler, 1942) and display lower activity levels compared with pigmented conspecifics (Fuller, 1967;DeFries, 1969). In particular, their activity is low during the day and increases during the night (Stryjek et al, 2013). Albino rats also spend longer periods in deep sleep (rapid eye PeerJ reviewing PDF | (2016:01:8597:1:0:NEW 13 Mar 2016)…”

“…Manuscript to be reviewed movement, REM), especially during the dark phase (Benca, Gilliland & Obermeyer, 1998), and during the night, they sleep more often out of the nests relative to pigmented conspecifics (Stryjek et al, 2013). Albino rats are slower to inhibit the fear response and explore new objects (Pisula et al, 2012), and they are less effective in completing spatial tasks (Harker & Whishaw, 2002).…”

Effect of light-dark changes on the locomotor activity in open field in adult rats and opossums

“…It is known that for the nocturnal animals light is a factor that influences locomotor activity and can be an aversive stimulus that provokes anxiety-like behaviour [8,18,19], especially in albino animals like Wistar rats [1,20].…”