Disturbances
of diurnal rhythms of biogenic amines contents in hypothalamic
nuclei as an evidence of neurotropic effects of enterotropic
carcinogen 1,2-dimethylhydrazine
by Alexander V. Arutjunyan, Gleb O. Kerkeshko, Vladimir
N. Anisimov, Mikhail G. Stepanov, Valentina M. Prokopenko,
Nikita V. Pozdeyev & Andrew V. Korenevsky
Keywords:
1,2-dimethylhydrazine, diurnal rhythms,
biogenic amines, melatonin, hypothalamus
Submitted:
June 28, 2001
Accepted: July 10, 2001
Abstract:
OBJECTIVES: Our data on the contents of norepinephrine
(NE), dopamine (DA) and the metabolite of serotonin 5-hydroxyindoleacetic
acid (5-HIAA) measured in the suprachiasmatic nuclei (SCN),
preoptic area (PA) and median eminence (ME) of hypothalamus
of rats after single subcutaneous injection of 1,2-dimethylhydrazine
(DMH) as well as the effect of this carcinogen on formation
of reactive oxygen species (ROS) in the PA are presented in
this paper.
RESULTS:
Diurnal changes of DA in all studied brain structures and
of NE in the PA have been observed in the control group. Their
morning levels were higher than evening ones. Rhythms of 5-HIAA
in the SCN and diurnal changes of ROS formation have been
shown to have contrary changes in control. Both the morning
(11 a.m.) and evening (11 p.m.) subcutaneous administration
of DMH at the dose of 21 mg/kg of body weight resulted in
changes of all rhythms observed in control. In some cases
a phase shift was found, in others the rhythms of neurotransmitters
and ROS formation disappeared entirely.
CONCLUSION:
The data obtained confirm the idea of dopaminergic and serotoninergic
systems taking part in mechanisms of a response of the hypothalamic
nuclei to non-photic stimuli. It is suggested that the effect
of DMH on the content and diurnal rhythms of neurotransmitters
in the hypothalamic structures under study is due to its affecting
activities of the enzymes of biogenic amines synthesis, synaptic
transmission, melatonin synthesis and secretion rhythms. The
change in ROS formation that is caused by administration of
DMH is likely to be due to a disturbance of diurnal rhythms
of neurotransmitters that are one of the sources of formation
of free radicals in the brain.
