Time Course of the Luteinizing Hormone Surge in Cannulated Rats: Quantitative Variance Estimates Within Individual Rats over Successive Cycles,2

Abstract

The present study was designed to compare quantitative variance estimates in the profile of the luteinizing hormone (LH) surge within individual rats over successive proestrous (PE) days (WITHIN) with the variability between rats (BETWEEN). Sprague-Dawley female rats were implanted under ether anesthesia with indwelling intracardiac cannulas. On successive PE afternoons of normal 4-day cycles, hourly blood samples (0.25 ml) were collected via the cannula from 1400-2000 h for radioimmunoassay of plasma LH. Three characteristics which reflected the profile of the LH surge were examined: the time of onset of LH release, the time of peak LH release, and the magnitude of peak LH release. Twenty-one animals yielded LH surge data on a total of 42 PE days with a mean (+/- SD) time of onset = 1534 h +/- 66 min, time of peak = 1730 h +/- 75 min, and magnitude of peak = 1176 +/- 441 ng NIAMDD-Rat LH-RP-1/ml plasma. Variance estimates BETWEEN and WITHIN animals were determined by analysis of variance and the method of Vaughan and Corballis (1969) for calculating percent of total variance. Differences BETWEEN in time of onset of LH release approached significance (P = 0.05-0.10) and contributed 50.5% of the total variance compared to a negative value for differences WITHIN. Differences BETWEEN in time of peak LH release were significant (P less than 0.05) and contributed 51.5% of total variance compared to a negative value for differences WITHIN. In contrast, for the magnitude of peak LH release, neither differences BETWEEN nor WITHIN contributed substantially to total variance (both negative values), with the major contribution from the residual term.(ABSTRACT TRUNCATED AT 250 WORDS)

Plasma Prolactin and Luteinizing Hormone Profiles during the Estrous Cycle of the Female Rat: Effects of Surgically Induced Persistent Estrus

“…Previous studies by Carillo and Sawyer [9] and Barofsky and Harney [1] have established that within individual ani mals the time of onset and the time of peak of the LH surge are very consistent over successive cycles. In this study we have confirmed these results, and also established that the time of onset and amplitude of the surge in plasma PRL is very consistent within individual animals on successive proestrous afternoons.…”

“…Schematic drawing, according to Konig and Klippel [22] and Paxinos and Wat son [29], illustrating the location and the ex tent of AMPO. SC'N and combined AMPO/ SCN lesions (shaded area in frames [1][2][3][4]. AC = Anterior commissure: AH = anterior hypothalamus: AMPO = anterior medial preoptic nucleus [29]: AR = arcuate nucleus; DB = diagonal band: f = fornix: MPA = medial preoptic area: OC = optic chiasm: RCH = retrochiasmatic area: re = nucleus reuniens; SCN = suprachiasmatic nucleus: VMH = ventromedial nucleus.…”

“…24, 42, 51], The timing oi the PRL and LH surges varies considerably between animals [1, 4, 9, 49]. However, within individual rats the timing of the LH surge on the afternoon of proestrus is very consistent over succes sive cycles [1,9].It has been known for a long time that knife cuts placed immediately behind the optic chiasm (OC) disrupt the esReceived: April 7, 1987 Accepted after revision: July 27, 1987 trous cycle and block the preovulatory surge of LH and PRL [5, 17, 20, 23,27], Lesion studies have suggested that the suprachiasmatic nucleus (SCN) controls phasic LH and PRL secretion [3, 12, 16,37,39]. Moreover, it has been dem onstrated that the anterior medial preoptic nucleus (AMPO [29]; also called medial preoptic nucleus [6,35, 46] and anteroventral periventricular nucleus [41]) is also involved in controlling the estrous cycle and the preovulatory release of LH [16, 31, 46.…”

“…Most importantly, on the afternoon of proestrus, ovulation is preceded by a sudden elevation (surge) in plasma PRL followed by a rapid rise in plasma LH [8. 24, 42, 51], The timing oi the PRL and LH surges varies considerably between animals [1,4,9,49]. However, within individual rats the timing of the LH surge on the afternoon of proestrus is very consistent over succes sive cycles [1,9].…”

Central Administration of Antiserum to Vasoactive Intestinal Peptide Delays and Reduces Luteinizing Hormone and Prolactin Surges in Ovariectomized, Estrogen-Treated Rats

“…These can then be excluded from further experimentation and analysis. Studies by others that examined the reproducibility of the proestrous LH surge in intact females showed that the timing, but not the magnitude of the LH surge was consistent over successive cycles [58, 59]. It was suggested that this consistency in the timing might reflect the regularity of the circadian clock.…”