Hypothalamic regulation of reproduction under the chronic influence of toluene and melatonin

Experiments on chronic administration of melatonin with and without chronic inhalation of toluene dosed at both maximal permissible concentration (50 mg/ml) and limited chronical range (500 mg/m3) have been carried out on female rats to discover their effects on biogenic amines system in hypothalamic structures related to gonadoliberin synthesis and secretion - preoptic area (PA) and median eminence (ME). Contents of biogenic amines in ME and especially in PA have been shown to have circadian variations with maximum in the morning in control group of rats.
The chronic effect of synchronizing agent melatonin (administered dissolved in drinking water in concentration of 10 pg/m l, at night during 2 months) on neotransmitters and their circadian variations in both hypothalamic structures proved surprisingly to be much alike the effect of toluene. Both chemicals cause the disturbances of normal circadian variations o f norepinephrine, dopamine and serotonine in PA and dopamine in ME. The simultaneous administration of toluene and melatonin showed likewise no synchronizing ability of the latter under the conditions described.