Norepinephrine Induces Releases of Both LH-RH from the Hypothalamus and LH from the Rat Pituitary in vitro.

The effects of norepinephrine (NE) on the release of luteinizing hormone (LH) and LH-releasing hormone (LH-RH) were examined in a sequential double chamber perifusion system by perifusing the medio-basal hypothalamus (MBH) and/or pituitaries excised from normal female rats in diestrus. When the pituitary alone or in sequence with the MBH was perifused with medium containing 200μg/ml of NE, the concentration of LH in the efflux was significantly (p<0.05) increased to the level 50-150 % over the pre-injection control, whereas medium without NE had no effect. Perifusion of the pituitary in sequence with the MBH produced a higher peak level of LH than that attained by the perifusion of the pituitary alone. Administration of NE induced a significant increase in LH-RH release from the MBH, although the medium alone had no effect. These data suggest that NE induces LH release from the pituitary both by increasing LH-RH release from the MBH and by its direct action on the pituitary.