1. School of Pharmacy (Pharmacology); University of Eastern Finland; P.O. Box 1627 FI-70211 Kuopio Finland
2. Present address: Orion Corporation Orion Pharma; P.O. Box 425 FI-20101 Turku Finland
3. Neuroscience Center; University of Helsinki; P.O. Box 56 FI-00790 Helsinki Finland
4. Faculty of Biological and Environmental Sciences, Department of Biosciences, Division of Physiology and Neuroscience; University of Helsinki; P.O. Box 56 FI-00790 Helsinki Finland