The concentration of norepinephrine, dopamine and serotonin in serum of Malpolon monspessulanus and Uromastix aegyptius during the different phases of the hibernation cycle

Abstract

1. 1. Analysis of catecholamines (CA) undertaken in this work revealed the occurrence of highly significant declines in norepinephrine (NE) and dopamine (DA) levels in serum and brain of both Malpolon monspessulanus and Uromastix aegyptius during entrance into and during deep hibernation. These results suggest that CA synthesis is retarded during cold winter. 2. 2. The serum NE exhibited a marked and highly significant increase in arousing M. monspessulanus while the increase was more limited in U. aegyptius, and remained lower during arousal than when active. On the other hand, the serum DA showed significant decreases in both animals during arousal. 3. 3. The analyses also revealed that CA concentrations in brains of both animals were extremely high during arousal. The recorded sharp increase in CA level during arousal from hibernation implies the rapid activation and de novo synthesis of enzymes involved in the formation of CA. 4. 4. The declines in serotonin (5-hydroxytryptamine; 5-HT) levels in serum and brain of both M. monspessulanus and U. aegyptius during the different phases of the hibernating cycle were highly significant. These observations might reflect the occurrence of increased activity of serotonergic neurons and the rate of catabolism and turnover of 5-HT during hibernation.