Role of neuropsin in parvalbumin immunoreactivity changes in hippocampal basket terminals of mice reared in various environments

• Published in: Frontiers in cellular neuroscience Vol. 8; p. 420
• Main Authors: Suzuki, Harumitsu, Kanagawa, Dai, Nakazawa, Hitomi, Tawara-Hirata, Yoshie, Kogure, Yoko, Shimizu-Okabe, Chigusa, Takayama, Chitoshi, Ishikawa, Yasuyuki, Shiosaka, Sadao
• Format: Journal Article
• Language: English
• Published: Switzerland Frontiers Research Foundation 10.12.2014; Frontiers Media S.A
• Subjects: Animal cognition; Behavioral plasticity; Environmental effects; ErbB-2 protein; ErbB4; Fibers; GABA; Hippocampus; Immunoreactivity; interneuron; Interneurons; Kallikrein; Memory; mRNA; Neural networks; Neuregulin; Neuregulin 1; Neuregulin1; Neurons; Neuroscience; Neurotransmission; Parvalbumin; Plasticity (neural); Proteins; Pyramidal cells; Schizophrenia; synaptic plasticity; Variance analysis; γ-Aminobutyric acid; Japan; hippocampus; ErbB4; GABA; neuregulin1; interneuron; synaptic plasticity; KLK8
• ISSN: 1662-5102; 1662-5102
• DOI: 10.3389/fncel.2014.00420

In vitro approaches have suggested that neuropsin (or kallikrein 8/KLK8), which controls gamma-aminobutyric acid (GABA) neurotransmission through neuregulin-1 (NRG-1) and its receptor (ErbB4), is involved in neural plasticity (Tamura et al., 2012, 2013). In the present study, we examined whether parvalbumin (PV)-positive neuronal networks, the majority of which are ErbB4-positive GABAergic interneurons, are controlled by neuropsin in tranquil and stimulated voluntarily behaving mice. Parvalbumin-immunoreactive fibers surrounding hippocampal pyramidal and granular neurons in mice reared in their home cage were decreased in neuropsin-deficient mice, suggesting that neuropsin controls PV immunoreactivity. One- or two-week exposures of wild mice to novel environments, in which they could behave freely and run voluntarily in a wheel resulted in a marked upregulation of both neuropsin mRNA and protein in the hippocampus. To elucidate the functional relevance of the increase in neuropsin during exposure to a rich environment, the intensities of PV-immunoreactive fibers were compared between neuropsin-deficient and wild-type (WT) mice under environmental stimuli. When mice were transferred into novel cages (large cages with toys), the intensity of PV-immunoreactive fibers increased in WT mice and neuropsin-deficient mice. Therefore, behavioral stimuli control a neuropsin-independent form of PV immunoreactivity. However, the neuropsin-dependent part of the change in PV-immunoreactive fibers may occur in the stimulated hippocampus because increased levels of neuropsin continued during these enriched conditions.