Frye C A, Gardiner S G
Neuroscience Program, Department of Psychology, Connecticut College, New London 06320, USA.
Horm Behav. 1996 Dec;30(4):682-91. doi: 10.1006/hbeh.1996.0069.
In rats, progesterone (P) facilitates sexual receptivity by interacting with intracellular progestin receptors in the ventromedial hypothalamus (VMH). This experiment concerns whether P can also facilitate receptivity in rats by acting extragenomically within the ventral tegmental area (VTA). Ovariectomized rats (n = 10) with bilateral guide cannulas over the VMH and VTA were primed with 2 microg subcutaneous estradiol benzoate 44 hr prior to testing. After a pretest for sexual receptivity, animals received implants to the VMH of P, P conjugated to bovine serum albumin (P:BSA), or cholesterol control (CHOL), and were retested. Two hours later, animals were again tested for receptivity, and P, P:BSA, the P metabolite 5alpha-pregnan-3alpha-ol-20-one (3alpha,5alpha-THP), or CHOL implants were applied to the VTA. Subjects were retested immediately, 30, 90, and 150 min later. Animals that received P in the VMH and had P, P:BSA, or 3alpha,5alpha-THP applied to the VTA exhibited facilitated receptivity at all time points compared with all other combination implants. That P:BSA and P were equally effective when applied to the VTA, but not the VMH, suggests that in the VTA P's membrane-mediated actions are sufficient to facilitate receptivity, whereas in the VMH they are not. Since the steroid (P) and its metabolite (3alpha,5alpha-THP) are similarly effective when applied to the VTA, given P application to the VMH earlier, P's effects in the VTA may be subsequent to metabolism and/or actions at GABA receptors. Overall, these data suggest that in rats P can act at the membrane of neurons within the VTA to modulate lordosis and that these effects may be subsequent to P's metabolism and/or actions at GABA receptors.
在大鼠中，孕酮（P）通过与腹内侧下丘脑（VMH）中的细胞内孕激素受体相互作用来促进性接受能力。本实验探讨P是否也能通过在腹侧被盖区（VTA）内进行基因组外作用来促进大鼠的接受能力。在测试前44小时，对10只双侧在VMH和VTA上方植入引导套管的去卵巢大鼠皮下注射2微克苯甲酸雌二醇进行预处理。在进行性接受能力的预测试后，动物在VMH中植入P、与牛血清白蛋白结合的P（P:BSA）或胆固醇对照物（CHOL），并再次进行测试。两小时后，再次测试动物的接受能力，并在VTA中植入P、P:BSA、P代谢物5α-孕烷-3α-醇-20-酮（3α,5α-THP）或CHOL。在植入后立即、30分钟、90分钟和150分钟对受试者再次进行测试。与所有其他组合植入物相比，在VMH中接受P并在VTA中植入P、P:BSA或3α,5α-THP的动物在所有时间点的接受能力均得到促进。当应用于VTA而非VMH时，P:BSA和P具有同等效力，这表明在VTA中，P的膜介导作用足以促进接受能力，而在VMH中则不然。由于当应用于VTA时，类固醇（P）及其代谢物（3α,5α-THP）具有相似的效力，且先前已将P应用于VMH，因此P在VTA中的作用可能继发于其代谢和/或对GABA受体的作用。总体而言，这些数据表明，在大鼠中，P可作用于VTA内神经元的膜来调节脊柱前凸，且这些作用可能继发于P的代谢和/或对GABA受体的作用。
