title: Correlated alterations in serotonergic and dopaminergic modulations at the hippocampal mossy fiber synapse in mice lacking dysbindin.
abstract: Dysbindin-1 (dystrobrevin-binding protein 1, DTNBP1) is one of the promising schizophrenia susceptibility genes. Dysbindin protein is abundantly expressed in synaptic regions of the hippocampus, including the terminal field of the mossy fibers, and this hippocampal expression of dysbindin is strongly reduced in patients with schizophrenia. In the present study, we examined the functional role of dysbindin in hippocampal mossy fiber-CA3 synaptic transmission and its modulation using the sandy mouse, a spontaneous mutant with deletion in the dysbindin gene. Electrophysiological recordings were made in hippocampal slices prepared from adult male sandy mice and their wild-type littermates. Basic properties of the mossy fiber synaptic transmission in the mutant mice were generally normal except for slightly reduced frequency facilitation. Serotonin and dopamine, two major neuromodulators implicated in the pathophysiology of schizophrenia, can potentiate mossy fiber synaptic transmission probably via an increase in cAMP levels. Synaptic potentiation induced by serotonin and dopamine was very variable in magnitude in the mutant mice, with some mice showing prominent enhancement as compared with the wild-type mice. In addition, the magnitude of potentiation induced by these monoamines significantly correlated with each other in the mutant mice, indicating that a subpopulation of sandy mice has marked hypersensitivity to both serotonin and dopamine. While direct activation of the cAMP cascade by forskolin induced robust synaptic potentiation in both wild-type and mutant mice, this forskolin-induced potentaition correlated in magnitude with the serotonin-induced potentiation only in the mutant mice, suggesting a possible change in coupling of receptor activation to downstream signaling. These results suggest that the dysbindin deficiency could be an essential genetic factor that causes synaptic hypersensitivity to dopamine and serotonin. The altered monoaminergic modulation at the mossy fiber synapse could be a candidate pathophysiological basis for impairment of hippocampus-dependent brain functions in schizophrenia.
authors: Department of Pharmacology, Nippon Medical School, Tokyo, Japan. kkatsu-tky@umin.ac.jp
authors: Katsunori
authors: K
authors: Kobayashi
authors: Satomi
authors: S
authors: Umeda-Yano
authors: Hidenaga
authors: H
authors: Yamamori
authors: Masatoshi
authors: M
authors: Takeda
authors: Hidenori
authors: H
authors: Suzuki
authors: Ryota
authors: R
authors: Hashimoto
mesh_terms: D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism*; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D005576:Colforsin / Q000494:pharmacology; D004298:Dopamine / Q000378:metabolism*; D000074765:Dysbindin; D049029:Dystrophin-Associated Proteins; D008297:Male; D051379:Mice; D008818:Mice, Neurologic Mutants; D019599:Mossy Fibers, Hippocampal / Q000187:drug effects / Q000378:metabolism*; D017447:Receptors, Dopamine D1 / Q000378:metabolism; D012701:Serotonin / Q000378:metabolism*; D009435:Synaptic Transmission / Q000187:drug effects
chemical_list: D002352:Carrier Proteins; C498992:Dtnbp1 protein, mouse; D000074765:Dysbindin; D049029:Dystrophin-Associated Proteins; D017447:Receptors, Dopamine D1; D005576:Colforsin; D012701:Serotonin; D004298:Dopamine