[Correlations between specific binding of labeled adrenoligands of the brain and plasma testosterone in mice]

Correlations between specific binding of labeled adrenoligands in the frontal cortex and hypothalamus and peripheral blood plasma testosterone were studied in BALB/cLac, CBA/Lac, and S57BL/6J male mice. A negative correlation was detected between blood testosterone and the extent of specific binding of 3H-clonidine, a 1.6 nM alpha 2-adrenoceptor agonist, in the hypothalamus. No correlations were revealed between specific binding of 3H-clonidine in the frontal cortex and binding of the rest radioligands (0.4 nM alpha 1-adrenoceptor antagonist 3H-prazosin and 1.6 nM beta-adrenoceptor antagonist 3H-dihydroalprenolol) in both brain segments and blood testosterone level. Further experiments in six mouse strains (A/He, BALB/cLac, CBA/Lac, C57BL/6J, DD, and YT) revealed a reliable negative genotypic correlation between hypothalamic maximal specific binding of 3H-clonidine and testosterone level. The detected feedback may be an important regulatory mechanism of the hypothalamo-hypophyseo-gonadal system in male mice.