Norepinephrine induces releases of both LH-RH from the hypothalamus and LH from the rat pituitary in vitro.

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Abstract
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 200 .mu.g/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. Evidently NE induces LH release from the pituitary both by increasing LH-RH release from the MBH and by its direct action on the pituitary.