Article ID:
The bed nucleus of the stria terminalis (BNST) is one of the brain areas densely innervated by noradrenergic neurons originating in the brain stem. The present study aims to determine the role of noradrenergic receptors in the BNST in regulating pulsatile luteinizing hormone (LH) secretion in female rats. Ovariectomized (OVX) or estrogen-primed OVX (OVX+E2) rats received three 1-h-interval injections of 0.05 μmol of noradrenaline (NA), phenylephrine (α1-adrenergic receptor agonist), clonidine (α2-agonist), or isoproterenol (β-agonist) into the BNST. Injection of NA or α1-adrenergic agonist into the BNST strongly suppressed pulsatile LH secretion in OVX+E2 rats with a significant (P<0.05) decrease in the mean LH level for 3 h and LH pulse frequency, but α2-and β-agonists did not affect any of the LH pulse parameters. In OVX animals, α1- and α2-adrenergic agonists caused a significant change in LH pulse frequency and amplitude, respectively, though the effect was not as apparent as the NA- or α1-agonist-induced changes in OVX+E2 animals. These results indicate that NA inputs to the BNST suppress pulsatile LH secretion via α1-adrenergic receptors and that estrogen enhances this suppression.
