Over the training period, both knockout and wild-type mice learned to locate the hidden platform but upon platform removal, Decitabine supplier Mbnl2 knockouts crossed over the location of the platform significantly fewer times than wild-type mice, indicating a deficit in spatial reference memory

( Figure 3C). Since Mbnl2 knockouts exhibited impaired spatial memory on a hippocampal-dependent task, we performed electrophysiological recordings on hippocampal slices to evaluate the effects of Mbnl2 loss on NMDA receptor (NMDAR)-mediated synaptic transmission and synaptic plasticity (long-term potentiation [LTP]). Input-output curves of the NMDAR-mediated component of the field excitatory postsynaptic potentials (EPSPs) indicated significant effects of stimulation intensity [F (7, 161) = 91.77, p < 0.0001] exhibiting a decreased response in Mbnl2 knockouts when compared to wild-type selective HDAC inhibitors controls [F (1, 161) = 21.94, p < 0.0001] ( Figures 3D and 3E). The decrease in the NMDAR component of synaptic transmission was not due to a loss of synaptic input since the presynaptic fiber volley amplitude

was similar across the two groups ( Figure 3F). Furthermore, the input-output curves of the slope of the synaptic responses were not significantly different between Mbnl2 wild-type and knockout mice (data not shown), indicating that the difference was specific for NMDAR function. For analysis of synaptic plasticity, LTP-inducing stimulation was delivered to the test pathway. Although pattern stimulation induced LTP in wild-type mice compared to the nontetanized path [F (1, 11) = 16.63, p < 0.001], this LTP induction was not observed in five out of six Mbnl2 knockout mice (wild-type, 134.6 ± 8.09; Mbnl2 knockout,

104.9 ± 5.96) ( Figure 3G). Thus, loss of Mbnl2 expression results in decreased synaptic NMDAR activity, impaired LTP, and learning and memory deficits. Another neurologic phenotype, which emerged with low penetrance (<10%) next in Mbnl2 homozygous knockout males prior to weaning, was extreme hyperactivity followed by tonic-clonic seizures and death within 24 hr. To determine whether Mbnl2 deficiency promoted seizure activity, we compared Mbnl2 wild-type with heterozygous and homozygous male knockouts for seizure susceptibility using the GABA antagonist pentylenetetrazole (PTZ). After intraperitoneal injection of PTZ, mice were evaluated for seizure activity using a modified Racine scale and by measuring the time to the initial appearance of abnormal behavior (latency time). Remarkably, a low PTZ dose (40 mg/kg) was sufficient to generate enhanced seizure incidence, including tonic-clonic and clonic seizures, even in Mbnl2 heterozygous knockout mice ( Figure 3H).