“…A large number of physiological rhythmic variables are apparent in the central nervous system, in hormone secretion, and so on (Thomson et al, 1980;Kafka et al, 1981). In addition, many drugs vary in potency and/or toxicity according to the time in the circadian cycle when they are administered (Walker and Owasoyo, 1974;Frederickson et al, 1977;Ohdo et al, 1995Ohdo et al, , 1996Ohdo et al, , 2001).…”