Effects of 1,2-dihydro-4-hydroxy-6-methoxy-N-methyl quinoline in relation to circadian rhythms of NAD+ kinase and NADP+ autoreduction in Neurospora crassa and bioluminescence in Gonyaulax polyedra

1. In Neurospora crassa strain bd a, circadian rhythmicity was investigated in constant darkness. In the growing front of solid agar cultures, conidiation was preceded by a maximum of NAD+ kinase activity. The enzyme rhythmicity was suppressed by culturing mycelial discs in liquid medium, but became detectable again when this treatment was followed by 3 hr of air exposure. 2. In air-exposed discs, the circadian maximum of NAD+ kinase was enhanced by about 3-fold and advanced by about 3 hr upon administration of 1,2-dihydro-4-hydroxy-6-methoxy-N-methyl-quinoline (DHMMQ), whereas melatonin tended to reduce this rhythm. 3. DHMMQ stimulated the autoreduction of NADP+, the maximum of which followed that of NAD+ kinase. 4. Bioluminescence was measured in the dinoflagellate Gonyaulax polyedra, which was transferred from a light/dark cycle of 12:12 hr to constant darkness. 5. DHMMQ stimulated light emission up to more than 13-fold. When given at the low concentration of 10−6 M, the sensitivity towards DHMMQ varied greatly within the circadian cycle; the maximum of responsiveness occurred 3 hr after the onset of darkness, whereas no effects were seen in the late part of subjective night and during subjective day.