Chlorprothixene

Briefly, mice were box-anesthetized with 2% halothane in O₂/N₂O (1:1) and injected with atropine (0.1 mg/mouse s.c.; Franz Köhler), dexamethasone (0.2 mg/mouse s.c.; Ratiopharm), and chlorprothixene (0.2 mg/mouse i.m.; Sigma). After placing mice in a stereotaxic frame, anesthesia was maintained with 0.8% halothane in a 1:1 mixture of O₂/N₂O. An incision of the skin was made over the visual cortex and low-melting point agarose (2.5% in 0.9% NaCl) and a glass coverslip were placed over the exposed area.

All animal procedures were carried out according to the guidelines of the University of Zurich, and were approved by the Cantonal Veterinary Office. C57BL/6 mice (2–4 months old, of either sex) were either first sedated with chlorprothixene (Sigma; 0.2 mg/mouse) and anaesthetized with urethane (0.5–1.0 g/kg) or anaesthetized by 2.7 ml/kg of a solution containing one part fentanyl citrate and fluanisone (Hypnorm; Janssen-Cilag, UK) and one part midazolam (Hypnovel; Roche, Switzerland) in two parts of water, both delivered by intraperitoneal injections. Atropine (0.3 mg/kg) and dexamethasone (2 mg/kg) were administered subcutaneously to reduce secretions and oedema. Lactate-Ringer solution was regularly injected subcutaneously to prevent dehydration. Pinch reflexes were used to assess the depth of anaesthesia.

To determine the extent of muscimol infusion, cortical activity was recorded in the animals infused with muscimol or vehicle for >48 h (two vehicle-infused hemispheres and four muscimol-infused hemispheres). Both groups of animals were restrained in a stereotaxic instrument under anesthesia with 1.5%–3.0% isoflurane in O₂ and sedation with chlorprothixene (0.5 mg/kg, i.m., Sigma-Aldrich, St. Louis, MO, USA). The body temperature was maintained at 37°C by a temperature controller (NS-TC10, NeuroScience, Tokyo, Japan). Skin was incised on the head. All incisions were infiltrated with xylocaine. A square hole (2 mm × 4 mm) was made on the skull above the OFC (stereotaxic position, anterior 2.8 mm–4.8 mm to bregma and lateral 0 mm–4.0 mm to midline). A tungsten electrode (1 MΩ, UNIQUE MEDICAL, Tokyo, Japan) was inserted at various distances and depths to the site of muscimol infusion. Neural activity was filtered at 500–5000 Hz and amplified 1000-fold by an amplifier (Model 1800, A-M systems Inc., Sequim, WA, USA). When no spontaneous activity or injury discharge was observed, we judged the site as inactivated. After recording, electrolytic lesions were made to mark the position of recording sites at two different depths by applying an electrode (−) current of 1 μA for 10 s.