Do androgen receptors contribute to the expression of sex differences in the brain?

嗅球的传入终止于内侧杏仁核（MA）神经元，然后投射到内侧视前区（MPOA）在雄性大鼠或腹内侧下丘脑（VMH）在雌性大鼠。雄性大鼠的MPOA和雌性大鼠的VMH是性欲中枢。为了了解性腺激素对MA和MPOA神经元的影响，在小鼠脑切片制备中从这些神经元进行细胞内记录。MA神经元的平均静息膜电位和输入电阻分别为-68 ± 7 mV和76 ± 46 MΩ; MPOA神经元的平均静息膜电位和输入电阻分别为-68 ± 10 mV和140 ± 113 M Ω。在MA神经元和MPOA神经元中，峰电位的平均阈值和幅度分别为-54 4 mV和73± 7 mV，-55 3 mV和74± 3 mV。雄性和雌性小鼠之间的静息和活动膜特性之间没有差异。在雄性和雌性小鼠中，快兴奋性突触后电位（fast excitatory postsynaptic potentials，fast EPSPs）主要由AMPA/红藻氨酸型谷氨酸受体介导。MA神经元的快速抑制性突触后电位（fast inhibitory postsynaptic potentials，fast IPSPs）由γ-氨基丁酸（GABA）A受体介导。在雄性和雌性小鼠的MA和MPOA神经元中，17β-雌二醇（1 nM）的给药增加了快EPSP的振幅，降低了快IPSP的振幅。在MA神经元中，睾酮（100 nM）的管理增强了雄性小鼠的快速EPSP的幅度，但降低了雌性小鼠。这些结果表明，睾酮增强输入到雄性小鼠MA神经元引起的兴奋性反应，然后将信息传递到性欲中心，但在雌性小鼠中，睾酮诱导相反的反应。

Inputs from the olfactory bulb terminate in the medial amygdaloid nucleus (MA) neurons and then project to the medial preoptic area (MPOA) in male rats or the ventromedial hypothalamus (VMH) in female rats. The MPOA in male rats and the VMH in female rats are the center of sexual desire. To understand the effects of gonadal hormones on the MA and MPOA neurons, intracellular recordings were made from these neurons in mouse brain slice preparations. The mean resting membrane potential and input resistance were -68 ± 7 mV and 76 ± 46 MΩ in the MA neurons and -68 ± 10 mV and 140 ± 113MΩ in the MPOA neurons, respectively. The mean threshold and the amplitude of the spike were -54Ω4mV and 73±7mV in the MA neurons and -55±3mV and 74±3mV in the MPOA neurons, respectively. No difference existed between the resting and active membrane properties between male and female mice. The fast excitatory postsynaptic potentials (fast EPSPs) were mainly mediated by AMPA/kainate type glutamate receptors in both male and female mice. The fast inhibitory postsynaptic potentials (fast IPSPs) were mediated by γ-aminobutylic acid (GABA) A receptors in the MA neurons. The administration of 17β-estradiol (1 nM) augmented the amplitude in the fast EPSP and reduced it in the fast IPSP in both the MA and MPOA neurons in male and female mice. In the MA neurons, the administration of testosterone (100 nM) augmented the amplitude of fast EPSP in male mice, but reduced it in female mice. These results suggest that testosterone augments the excitatory responses induced by inputs to the MA neurons in male mice and then transmits information to the center of sexual desire, but in female mice testosterone induces the opposite responses.