[1] BAYLOR COLL MED,DEPT PHYSIOL & MOLEC BIOPHYS,HOUSTON,TX 77030
[2] UNIV PENN,DEPT PHARMACOL,PHILADELPHIA,PA 19104
[3] NATL POLYTECH INST,CINVESTAV,DEPT FISIOL BIOFIS & NEUROCIENCIAS,MEXICO CITY 14,DF,MEXICO
[4] UNIV PENN,MAHONEY INST NEUROSCI,PHILADELPHIA,PA 19104