Pankevich D E, Deedy E M, Cherry J A, Baum M J
Department of Biology, Boston University, 5 Cummington Street, Boston, MA 02215, USA.
Behav Brain Res. 2003 Sep 15;144(1-2):157-65. doi: 10.1016/s0166-4328(03)00073-1.
Volatile urinary odors contribute to mate recognition in mice after their detection by the main olfactory epithelium (MOE). We used a habituation/dishabitution task to ask whether the capacity of gonadectomized mice of both sexes to detect and investigate decreasing concentrations of volatile urinary odors from either breeding males or estrous females is modulated by administering androgen or estrogen and if so, whether any effects of these sex steroids are altered by disrupting the sympathetic innervation of the MOE via bilateral superior cervical ganglionectomy (SCGx). In tests given, beginning 51 days after gonadectomy without steroid treatment both male and female subjects detected even the lowest concentrations (1:120 and 1:160 dilutions by volume) of male urinary odors, provided they were SCGx as opposed to sham operated. In subsequent tests given after estradiol benzoate (EB) followed later by 5alpha-dihydrotestosterone (DHT) treatments, neither male nor female subjects detected low concentrations of male urinary odors regardless of whether or not their SCG's were intact. Administration of testosterone (T) prior to a final series of tests restored the ability of gonadectomized subjects of both sexes to detect low concentrations of male urinary odors regardless of their SCG status. This suggests that T, but not its neural metabolites estradiol, or DHT, facilitates responsiveness to low concentrations of male odors in mice of both sexes. In tests given 51 days after gonadectomy without steroid treatment most male and female subjects readily detected the three highest concentrations of estrous female urinary odors whereas SCGx males and females failed to detect the lowest concentrations of these odors. After treatment with EB and then with DHT, gonadectomized mice of both sexes generally failed to detect the three lowest concentrations of estrous female urinary odors regardless of their SCG status. After T treatment; however, subjects of both sexes again detected most dilutions of estrous female urine, provided their SCG's were intact. Again, these results suggest that T, but not estradiol or DHT, facilitates responsiveness to estrous female urinary odors. Provided such an activational effect of T is present, sympathetic, noradrenergic inputs to the MOE may enhance odorant contrast, as previously suggested [Nat. Neurosci. 2 (1999) 106], by reducing the responsiveness of olfactory neurons to low (1:120 and 1:160 dilutions) concentrations of some biologically significant odorants (e.g. male urinary odors) while facilitating their responsiveness to low to moderate (1:80 dilution) concentrations of others (e.g. estrous female urinary odors).
挥发性尿液气味在被主嗅上皮（MOE）检测到后有助于小鼠识别配偶。我们采用习惯化/去习惯化任务来探究，对于来自繁殖期雄性或处于发情期雌性的挥发性尿液气味，给予雄激素或雌激素是否会调节两性去势小鼠检测和探究其浓度递减的能力；如果会，通过双侧颈上神经节切除术（SCGx）破坏MOE的交感神经支配是否会改变这些性类固醇的任何作用。在去势后51天且未进行类固醇治疗的情况下进行的测试中，无论雄性还是雌性受试者，只要他们接受了SCGx而非假手术，即使是最低浓度（按体积1:120和1:160稀释）的雄性尿液气味也能被检测到。在随后给予苯甲酸雌二醇（EB）、之后再给予5α-二氢睾酮（DHT）治疗后的测试中，无论其SCG是否完整，雄性和雌性受试者都无法检测到低浓度的雄性尿液气味。在最后一系列测试之前给予睾酮（T），恢复了两性去势受试者检测低浓度雄性尿液气味的能力，无论其SCG状态如何。这表明，是T而非其神经代谢产物雌二醇或DHT，促进了两性小鼠对低浓度雄性气味的反应性。在去势后51天且未进行类固醇治疗的测试中，大多数雄性和雌性受试者都能轻易检测到发情期雌性尿液气味的三个最高浓度，而接受SCGx的雄性和雌性则无法检测到这些气味的最低浓度。在用EB然后用DHT治疗后，无论其SCG状态如何，两性去势小鼠通常都无法检测到发情期雌性尿液气味的三个最低浓度。然而，在T治疗后，只要SCG完整，两性受试者再次能检测到发情期雌性尿液的大多数稀释度。同样，这些结果表明，是T而非雌二醇或DHT，促进了对发情期雌性尿液气味的反应性。如果T存在这样的激活作用，如之前所提出的[《自然神经科学》2 (1999) 106]，MOE的交感去甲肾上腺素能输入可能通过降低嗅觉神经元对低浓度（1:120和1:160稀释）的一些具有生物学意义的气味剂（如雄性尿液气味）的反应性，同时促进它们对低至中等浓度（1:80稀释）的其他气味剂（如发情期雌性尿液气味）的反应性，来增强气味对比。
