Ralationship between noradrenergic nervous system activity and luteinizing hormone releasing hormone(LHRH) content mediated by testosterone in hypothalamus was tested. Three groups of adult male animals were prepared; (1) Intact; (2) Castration+Vehicle (Cast+V); (3) Castration+Testosterone (Cast+T). Silastic capsule containing vehicle or testosterone was implanted into neck region of animals two weeks following castration. Norepinephrine content, alpha-adrenergic receptor binding characteristics using H$^{3}$-WB4101, and content of LHRH by LHRH RIA procedure were determined. Testosterone replacement to castrated male rats augmented the content of norepinephrine and LHRH. Testosterone replacement increased the alpha-adrenergic receptor density but did not change alpha-receptor affinity. The data from the present study suggest that increase in LHRH content by testosterone may be positively coupled to the activity of central noradrenergic nervous system.