Estienne M J, Hurlock W F, Barb C R
Department of Agriculture, University of Maryland Eastern Shore, Princess Anne 21853, USA.
J Anim Sci. 1998 Aug;76(8):2162-8. doi: 10.2527/1998.7682162x.
The objective of this experiment was to determine the effects of n-methyl-d,l-aspartate (NMA), an agonist of the neurotransmitter glutamate, on circulating concentrations of LH, GH, and cortisol in gilts treated during the luteal (n = 4) or follicular (n = 4) phase of the estrous cycle, or after ovariectomy (n = 4). Blood was sampled every 15 min for 10 h on each of two consecutive days. On the 1st d, two gilts from each group received i.v. injections of NMA (10 mg/kg BW) at h 4 and 6, and the remaining gilts received .9% saline (vehicle). The following day, gilts that had received NMA on the 1st d received vehicle, and gilts that had received vehicle on d 1 received NMA. All gilts received an i.v. challenge of GnRH (.1 microg/kg BW) at h 8 on each day. The NMA treatment increased (P < .01) LH pulse frequency in luteal-phase gilts by 125%. In contrast, NMA decreased (P < .05) mean concentrations of LH by 48% and suppressed (P < .01) LH pulse frequency by 33% in ovariectomized gilts. No characteristics of LH secretion were affected (P > .05) by NMA in follicular phase gilts. Serum LH concentrations for the 2-h period following GnRH were lower (P < .05) in follicular-phase gilts than in ovariectomized gilts and were 1.15 +/- .09 (mean +/- SE), .81 +/- .05, and .51 +/- .17 ng/mL for ovariectomized, luteal-phase, and follicular-phase gilts, respectively. Treatment with NMA increased circulating concentrations of GH by 334% (P < .01) and cortisol by 77% (P < .03) in all gilts. We suggest that the effects of NMA on LH release in gilts depend on the circulating steroidal milieu. In contrast, NMA evokes secretion of GH and cortisol irrespective of the reproductive status of treated gilts.
本实验的目的是确定神经递质谷氨酸的激动剂N-甲基-DL-天冬氨酸（NMA）对处于发情周期黄体期（n = 4）或卵泡期（n = 4）的后备母猪，或卵巢切除术后（n = 4）的后备母猪循环血中促黄体生成素（LH）、生长激素（GH）和皮质醇浓度的影响。在连续两天中的每一天，每隔15分钟采集一次血样，共采集10小时。第1天，每组的两头后备母猪在第4小时和第6小时静脉注射NMA（10 mg/kg体重），其余后备母猪注射0.9%生理盐水（赋形剂）。第二天，第1天接受NMA注射的后备母猪注射赋形剂，第1天接受赋形剂注射的后备母猪注射NMA。所有后备母猪在每天的第8小时接受静脉注射促性腺激素释放激素（GnRH，0.1μg/kg体重）刺激。NMA处理使黄体期后备母猪的LH脉冲频率增加了125%（P < 0.01）。相反，NMA使卵巢切除术后的后备母猪的LH平均浓度降低了48%（P < 0.05），并使LH脉冲频率抑制了33%（P < 0.01）。NMA对卵泡期后备母猪的LH分泌特征没有影响（P > 0.05）。GnRH注射后2小时内，卵泡期后备母猪的血清LH浓度低于卵巢切除术后的后备母猪（P < 0.05），卵巢切除术后、黄体期和卵泡期后备母猪的血清LH浓度分别为1.15±0.09（平均值±标准误）、0.81±0.05和0.51±0.17 ng/mL。NMA处理使所有后备母猪的循环血中GH浓度增加了334%（P < 0.01），皮质醇浓度增加了77%（P < 0.03）。我们认为，NMA对后备母猪LH释放的影响取决于循环甾体环境。相反，无论处理的后备母猪的生殖状态如何，NMA均可引起GH和皮质醇的分泌。
