1. Department of Neuropharmacology, Astra Research Centre, S-151 85 Södertälje, Sweden, Department of Psychology, Unit of Psychobiology, University of Göteborg, PO Box 14158, S-400 20 Göteborg, Sweden
2. Department of Psychology, Unit of Psychobiology, University of Göteborg, PO Box 14158, S-400 20 Göteborg, Sweden