Optokinetic deficits in albino ferrets (Mustela putorius furo):
a behavioral and electrophysiological study
K.-P. Hoffmann, N. Garipis & C. Distler
Journal of Neuroscience, 24:4061-4069, 2004
- We compared the horizontal optokinetic reaction (OKR) and response properties of retinal slip neurons in the
nucleus of the optic tract and dorsal terminal nucleus (NOT-DTN) of albino and wild-type ferrets (Mustela putorius
furo). In contrast to pigmented ferrets, we were unable to observe OKR in albino ferrets during binocular and monocular
viewing using random dot full field stimulation and electro-oculography (EOG). Observations during early postnatal
life indicate that regular OKR is present in pigmented pups 3 d after eye opening but is absent at any stage during
development in albino ferrets. Unilateral muscimol injections to inactivate all neurons in the NOT-DTN containing
GABA(A) and GABA(C) receptors caused spontaneous horizontal nystagmus with slow phases away from the injected hemisphere
in albino as well as in pigmented animals. Retinal slip neurons in the NOT-DTN of albino ferrets identified by
antidromic activation from the inferior olive and orthodromic activation from the optic chiasm were well responding
to intermittent bright light stimuli, but many showed a profound reduction of responsiveness to moving stimuli.
The movement-sensitive neurons exhibited no clear direction selectivity for ipsiversive stimulus movement, a characteristic
property of these neurons in pigmented ferrets and other mammals. Thus, the defect rendering albino ferrets optokinetically
nonresponsive is located in the visual pathway subserving the OKR, namely in or before the NOT-DTN, and not in
oculomotor centers.
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