Recent advances in immunosuppressants.- Present status of hepatoprotectants.- The 5-HT1A receptor and its ligands: structure and function.- U-50,488 and the K receptor: a personalized account covering the period 1973-1990.- Protease inhibitors as potential antiviral agents for the treatment of picornaviral infections.- Index Vol. 52.- Index of titles, Vol. 1-52.- Author and paper index, Vol. 1-52.