Picrotoxin speeds the circadian clock in murine and human nonneural tissue but not Drosophila. A, top: PER2::LUC rhythms from representative lung explants cultured with vehicle or picrotoxin (500 μM); bottom: quantification of the period of lung under each condition (means ± SE, n = 3–4 per treatment; *P < 0.001). B, top: PER2::dLuc rhythms from representative primary human astrocytes cultured with vehicle or picrotoxin (100 μM); bottom: quantification of the period of human astrocyte cultures under each condition (n = 5 per treatment; *P < 0.001). C, top: Timeless::luciferase (Tim::Luc) rhythms from representative Drosophila abdomens cultured in vehicle or picrotoxin (500 μM); bottom: Drosophila Tim::Luc abdominal rhythms were unaffected by picrotoxin (n = 26 per treatment; P > 0.05). n.s., Not significant.