[Adrenergic mechanisms of the regulation of stages of chemical carcinogenesis: role of presynaptic receptors].

A modifying effect of a catecholamine precursor (L-DOPA, 20 mg/kg, intraperitoneally) on various stages (initiation and promotion) of hepatocarcinogenesis, induced by N-nitrosodiethylamine (NDEA, 85 mg per 1 litre of tap water) was studied in chronic experiments on 150 male rats. L-DOPA administration prior to NDEA (influence on initiation) stimulated hepatocarcinogenesis considerably, while its administration after NDEA (influence on promotion) inhibited the realization of a carcinogenic effect. A statistically significant decrease in noradrenaline hypothalamus content was identified during early stages of chemically induced neoplastic transformation of hepatic cellular elements (stages of diffuse and focal proliferation). The results are discussed in terms of the regulatory role of the tone of the adrenergic autonomous nervous system component at the level of presynaptic inhibitory receptors in realization of the chemical carcinogenic effect.