Classical eyeblink conditioning in glutamate receptor subunit delta 2 mutant mice is impaired in the delay paradigm but not in the trace paradigm.
In mice lacking glutamate receptor subunit delta 2 (GluR delta 2(-/-_ mice), cerebellar long-term depression (LTD) at the parallel fibre-Purkinje cell synapses is disrupted. Unlike the cerebellar LTD-deficient mice previously used for eyeblink conditioning, however, the abnormalities of the GluR delta 2(-/-) mice are restricted to the cerebellar cortex. In delay eyeblink conditionings (interstimulus interval of 252 and 852 ms), in which the conditioned stimulus (CS) overlaps temporally with a coterminating unconditioned stimulus (US), GluR delta 2(-/-) mice are severely impaired in learning, strongly supporting the hypothesis that cerebellar cortical LTD is essential for delay conditioning. In the trace paradigm, in which a stimulus-free trace interval of 500 ms intervened between the CS and US, GluR delta 2(-/-) mice learned as successfully as wild-type mice, indicating that cerebellar LTD is not necessary for trace conditioning. Thus, the present study has revealed a cerebellar LTD-independent learning in eyeblink conditioning.
Kishimoto
Y
Y
Laboratory of Neurobiophysics, School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
Kawahara
S
S
Suzuki
M
M
Mori
H
H
Mishina
M
M
Kirino
Y
Y
D000818:Animals; D001767:Blinking / Q000502:physiology*; D003214:Conditioning, Classical / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D008817:Mice, Mutant Strains / Q000235:genetics; D017470:Receptors, Glutamate / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D013997:Time Factors
D017470:Receptors, Glutamate; C107913:glutamate receptor delta 2