Fig. 4.

Blocking nlgn1 expression in the hippocampus impairs long-term memory. (A) Rats in CTL (○, saline; ▵, scrambled) and nlgn1 siRNA groups were matched for background performance in pretraining (F < 1). Rats in the saline and scrambled siRNA groups did not differ on any performance measure and were pooled for all subsequent analysis (CTL group). (B) There is no difference between groups in latency to locate the hidden platform during training (F < 1). Shown are blocks of two training trials each. (C) Rats that received nlgn1 siRNA took longer than those that received CTL injections (P < 0.05) to find the platform location in a probe test 48 h after training. (D and E) Rats in the CTL but not in the nlgn1 group spent more time (D; P < 0.02) and had more crossings (E; P = 0.05) in the target annulus than in other CTL annuli (averaged score shown). The CTL group also had significantly more crossings than the nlgn1 group in the target annulus (P < 0.03). There is no difference between rats that received nlgn1 and CTL injections in their latency to locate a visible platform in a cued training task given immediately after the probe test (data not shown), suggesting intact motivation and sensorimotor function. (F) In situ hybridization quantification of nlgn1 and nlgn2 after unilateral injection of nlgn1 siRNA (P < 0.05 for nlgn1).