Improvement of spontaneous alternation behavior deficit by activation of α4β2 nicotinic acetylcholine receptor signaling in the ganglioside GM3-deficient mice

We have reported that in ganglioside GM3-deficient (GM3^-/-) mice, spontaneous alternation behavior assessed by a Y-maze task was significantly lower, and total arm entries were significantly higher than in wild-type mice. The objective of the present study was to examine the role of nicotinic acetylcholine receptor (nAChR) signaling in impairment of spontaneous alternation behavior of GM3^-/- mice. Nicotine treatment (0.3, 1.0 mg/kg, s.c.) dose dependently improved the spontaneous alternation deficit without affecting total arm entries in GM3^-/- mice. The nicotine-induced (1.0 mg/kg, s.c.) improvement was significantly abolished by the nAChR antagonist mecamylamine (1.0 mg/kg, i.p.). The α4β2 nAChR antagonist dihydro-β-erythroidine (2.5, 10.0 mg/kg, i.p.) dose dependently counteracted the nicotine-induced improvement of spontaneous alternation in GM3^-/- mice, whereas the α7 nAChR antagonist methyllycaconitine (2.5, 10.0 mg/kg, i.p.) did not. In addition, the α4β2 nAChR agonist RJR-2403 (5.0, 10.0 mg/kg, s.c.) dose dependently and significantly improved the spontaneous alternation deficit, whereas the α7 nAChR agonist PNU120596 (0.3, 1.0, 3.0 mg/kg, i.p.) did not. These findings revealed that nicotine improved spontaneous alternation behavior of GM3^-/- mice via the activation of α4β2, but not α7, nAChR. Thus, the ganglioside GM3 might be responsible for α4β2 nAChR signaling in the spontaneous alternation behavior.