How do albino rats differ from pigmented rats?


Albino rats have a number of differences from pigmented rats that stem from the albino's inability to produce melanin. This inability to produce pigment does more than produce differences in appearance -- the well-known white fur and pink eyes. Albino rats also have impairments of vision, sense of smell, motor skills, and spatial learning, and sleep patterns.


Albino rats have impaired vision

Albino rats have impaired vision as compared to normally pigmented rats. Albino rats have fewer light sensitive cells in their eyes, an abnormal eye-to-brain connection, and a translucent iris which leads to dazzling and retinal degeneration. Albino rats also take much longer than pigmented rats to adapt to low-light conditions. As a consequence of all these differences, albino rats are severely visually impaired or blind.


Albino rats have an impaired sense of smell

Albino rats have a dulled sense of smell and/or reduced responsivity to smells.

Albinos take much longer to back away from a pungent-smelling piece of garlic than normally pigmented rats. Albino rats are also largely unresponsive to the odor of a female rat in heat. When albino and pigmented males are separated from a female in heat by two wire mesh screens, so they can see and smell her but not touch her, nearly all the pigmented males became aroused, but almost none of the albino rats did.


Albino rats have impaired motor skills

Albino rats are clumsier than pigmented rats.

Specifically, albino rats use different and poorer-quality forearm movements than pigmented rats when reaching for a food pellet. The movements of albino rats resemble those of pigmented rats with motor system injury. In spite of their clumsiness, the albino rats in this experiment were as successful as pigmented rats in acquiring the food pellet (Whishaw et al. 2003). 


Albino rats have an impaired ability to learn spatial tasks

Albino rats perform more poorly than pigmented rats on place and matching-to-place spatial learning tasks (Troy and Whishaw 2002) and spatial navigation tasks (Tonkiss et al.1992).


Albinos have different patterns of REM sleep

Albino rats have different systems involved in regulating sleep-waking patterns and REM sleep responses to light.

Albino rats spend more of their REM sleep in the dark, while pigmented rats spend more of their REM sleep during the light (Benca et al. 1998). In addition, increasing the light intensity has a far greater effect on albino REM sleep than on the REM sleep of pigmented rats (Obermeyer and Benca 1999).

Both albino and pigmented rats have similar patterns of waking and non-REM sleep in the light and dark, with more non-REM sleep in the light and more wakefulness in the dark. The brighter the light, the more this NREM sleep-wake difference is accentuated (Obermeyer and Benca 1999).

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