Authors: Peter Kamerman Duncan Mitchell Helen Laburn
Publish Date: 2001/10/23
Volume: 443, Issue: 4, Pages: 609-616
Abstract
We have investigated whether there is circadian variation in the effects of nitric oxide synthase inhibitors on body temperature physical activity and feeding We used nocturnally active SpragueDawley rats housed at ≅24°C with a 1212 h lightdark cycle lights on 0700 hours and provided with food and water ad libitum Nitric oxide synthesis was inhibited by intraperitoneal injection of the unspecific nitric oxide synthase inhibitor NnitroLarginine methyl ester LNAME 100 50 25 10 mg/kg or the relatively selective inducible nitric oxide synthase inhibitor aminoguanidine 100 50 mg/kg during the day ≅0900 hours or night ≅2100 hours Body temperature and physical activity were measured using radiotelemetry while food intake was calculated by weighing each animals food before as well as 12 and 24 h after each injection We found that daytime injection of LNAME and aminoguanidine had no effect on daytime body temperature However daytime injection of both drugs did decrease nocturnal food intake P005 and activity P005 When injected at night LNAME reduced nighttime body temperature P001 activity P005 and food intake P005 in a dosedependent manner but nighttime injection of aminoguanidine inhibited only nighttime activity P005 The effects of nitric oxide synthase inhibition on body temperature feeding and activity therefore are primarily a consequence of inhibiting constitutively expressed nitric oxide synthase and are subject to circadian variation
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