Genetic ablation of tenascin-C expression leads to abnormal hippocampal CA1 structure and electrical activity in vivo.

Despite evidence that the extracellular matrix glycoprotein tenascin-C (TNC) is implicated in brain development and plasticity, its roles in the intact adult brain are unknown. Here we report that spontaneous local field potential (LFP) activity in freely moving adult TNC-deficient mice is abnormal. The power of cortical and hippocampal theta and gamma oscillations was enhanced in comparison to wild-type mice. The alteration in hippocampal gamma rhythm was subfield specific, such that CA1 gamma was accentuated while dentate gyrus gamma was normal. Similar to LFP, synaptic transmission and plasticity at perforant path synapses in the dentate gyrus were unaffected by the mutation. Morphological analyses revealed a subfield-specific reduction in the CA1 volume and a reduction in the numbers of somatostatin-positive interneurons in the hippocampus as potential structural substrates of the observed functional aberrations. These findings indicate a role for tenascin-C in structural organization of the CA1 hippocampal subfield and in shaping neural activity.