Rhythmic patterns of endogenous LH release in castrate sheep receiving exogenous LH (38477)

Exogenous ovine LH was constantly infused during 6-hr experimental sequences in order to determine the effect of elevated levels of plasma LH on the pulsatile discharges of pituitary LH characteristic of ovariectomized sheep. Plasma LH concentrations (exogenous plusendogenous) in sequential 10-min samples continued to fluctuate significantly as did plasma LH (endogenous only) during control periods. The temporal patterns of plasma LH during LH infusion were at least as as rhythmic as they were in the controls. Furthermore, the mean periods for extremely rhythmic frequencies were equivalent in control and LH-infusion sequences. These data refute the original hypothesis that inhibitory short-looped feedback of circulating LH governs the timing of subsequent LH discharges in ovariectomized sheep.