The effects of photoperiod on olfactory c-fos expression in prairie voles,Microtus ochrogaster

Reproduction stops among the majority of prairie voles (Microtus ochrogaster) during the winter. Short day lengths suppress male reproductive function dramatically in the laboratory, but photoperiod exerts only subtle effects on female reproductive function. Thus, the regulation of seasonal breeding in this species remains partially unspecified. In contrast to commonly studied rodents, female prairie voles do not undergo spontaneous estrous cycles; rather, they are induced into estrus by exposure to chemosignals expressed in conspecific male urine. In the present study, the hypothesis was tested that seasonal breeding among female prairie voles in the field reflects photoperiod-mediated changes in the responsiveness of the chemosensory system to male urine. Responsiveness was assessed by localizing the product of the c-fos immediate early gene with an immunocytochemical procedure. Female prairie voles were maintained in either long (LD 16:8) or short (LD 8:16) photoperiods from birth until adulthood, and exposed to either male urine or skim milk. Immunocytochemistry forfos protein revealed an increased number of immunoreactive cells within the accessory olfactory system of female prairie voles, including the accessory olfactory bulbs, granule cell layer, as well as the medial and cortical divisions of the amygdala 1 h after exposure to a single drop of urine as compared to individuals exposed to skim milk. The number of immunoreactivefos cells induced in females by conspecific male urine was also affected by photoperiod; short day females displayed fewer immunoreactivefos neurons in the accessory olfactory system as compared to long-day animal. Taken together, these results indicate that similar mechanisms underlie the responses of different rodent species to the chemosignals of conspecifics and that the pattern offos expression observed in the present study has functional significance for the regulation of reproduction in prairie voles.     

Effects of estrus cycle on thermoregulatory responses during exercise in rats

Summary In female rats, rectal temperature (T _re), tail vasomotor response, oxygen uptake , and carbon dioxide production were measured in proestrus and estrus stages during treadmill running at two different speeds at an ambient temperature (T _a) of 24° C. Experiments were performed at 2.00–6.00 a.m., when the difference inT _re was greatest between the two stages;T _re at rest in the estrus stage was 0.54° C higher than in the proestrus stage. In a mild warm environment, thresholdT _re for a rise in tail skin temperature (T _tail) was also higher in the estrus stage than in the proestrus stage. In contrast, no difference was seen in the thresholdT _re and steady stateT _re at the end of exercise between proestrus and estrus stages. These values were higher at the higher work intensity. was also similar between the two stages, except in the second 5 min after the beginning of exercise, when was greater andT _re rose more steeply in the proestrus stage. These data indicate that deep body temperature during exercise is regulated at a certain level depending on the work intensity and is not influenced by the estrus cycle.This study was supported in part by a Grant-in Aid for Scientific Research from the Ministry of Education, Science and Culture of Japan (Grant No. 62480114)     

Learning in escape/avoidance tasks in female rats does not vary with reproductive condition

To determine whether the development of novel stimulus-response associations by the mother during the periparturient period is attributable to a general facilitation of learning produced by the hormonal milieu during that period, learning ability under various reproductive conditions was assessed in two tasks unrelated to the periparturitional situation. The two tasks, selected because they equalized the various groups for motivation and performance variables, were acquisition of a water-maze escape (including two reversals), and acquisition and retention of an unsignalled shuttlebox shock avoidance. The groups tested in the water maze were a midpregnant group, an immediately prepartum group, and an immediately postpartum group. In the shuttlebox, the same conditions (different rats) were compared, together with a nonpregnant estrus condition, and a nonpregnant diestrus condition. The results of both experiments indicate that although learning occurred, the characteristics of acquisition and retention were not influenced by reproductive condition.     

冷冻应激对Wistar雌性大鼠生殖周期与生育能力的影响

目的为观察低温应激对大鼠生殖周期与生育能力的影响及人参多糖对其调节,本实验研究了Wistar雌性大鼠生殖周期与生育能力的变化规律及人参多糖的生物学效应。方法将Wistar大鼠分16℃对照组、4℃低温应激实验组与4℃低温应激人参多糖实验组,生殖器官的发育和生殖周期变化采用称重法与观察法。LH与FSH水平检测采用放免分析法。结果对照组、4℃低温应激实验组与4℃低温应激人参多糖实验组的卵巢重量分别为(36±1.20)g、(24±1.31)g和(27±1.14)g;子宫重量为(0.64±0.03)g、(0.45±0.01)g和(0.49±0.02)g;开口率为68%、39%和43%;LH和FSH为(0.28±0.04)ng/ml、(0.11±0.07)ng/ml和(0.14±0.05)ng/ml与(0.35±0.01)ng/ml、(0.17±0.03)ng/ml和(0.21±0.02)ng/ml;与对照组比较P<0.05。动情周期、怀孕率及生仔数,与对照组比较P<0.05。结论低温应激抑制大鼠生殖器官发育,使动情期延长,怀孕率降,LH与FSH分泌水平降低,人参多糖对其有上调作用。     

绵羊产后诱发发情试验

本试验利用多种方案对90只哺乳母羊采用羔羊提前断奶、公羊性刺激并结合激素处理发发情，以达到缩短产羔间隔，提高繁殖率的目的，经试验测定，母羊发情率平均为32.22%，情期受胎率平均为31.03%，效果不理想，需进一步对此进行研究。     

小鼠动情周期子宫内膜LIF基因表达研究

目的：探讨白血病抑制因子（LIF）基因在小鼠动情周期子宫内膜的表达情况。方法：采用RT－PRC技术对小鼠动情周期各个时期LIF基因表达进行检测。结果：动情周期、动情前期和动情期均未检测到LIF基因表达,而动情后期子宫内膜检测到LIF基因强表达。结论：推测LIF基因表达受母体自身激素水平改变的调控,且主要涉及孕激素,而与雌激素关系不大。     

雌性大鼠动情周期中黄体生成素细胞形态变化的图像分析

应用特异性的ａ－ｒＬＨβ抗血清，以ＡＢＣ技术显示垂体黄体生成素（ＬＨ）细胞，通过计算机图像处理系统对ＬＨ细胞的面积，、细胞内液泡面积和细胞形状等参数进行定量和统计分析，获得了大鼠正常动情周期各时期典型的ＬＨ细胞学图像。结果表明，ＬＨ的早期贮存和基础主要同细胞内颗粒变化有是ＬＨ的大量贮存和大量释放同细胞内液泡的变化以及由此产生的细胞大小、细胞形状和细胞结构等形态变化密切相关。提出ＬＨ细胞内液泡变化是     

Sex and estrus cycle differences in the modulatory effects of morphine on seizure susceptibility in mice

PURPOSE: To evaluate the effects of sex and estrus cycle on biphasic anticonvulsant and proconvulsant modulation of seizure threshold by morphine. METHODS: The threshold for the clonic seizures (CST) induced by acute intravenous administration of gamma-aminobutyric acid (GABA)-antagonist pentylenetetrazole (PTZ) was assessed in male and female mice. Estrus cycle was assessed by vaginal smears. The effect of removing circulating sex hormones was assessed by gonadectomy. RESULTS: At baseline, diestrus females had a higher CST compared with males and estrus females. Morphine at lower doses (0.5-3 mg/kg) had a significant anticonvulsant effect in males and estrus females compared with that in vehicle-treated controls, whereas female mice in diestrus phase showed a relative subsensitivity to this effect. Morphine at higher doses (30 and 60 mg/kg) significantly decreased CST in males and diestrus females, with less relative effect in estrus mice. In both phases, morphine exerted stronger effects in males compared with females. Ovariectomy brought the baseline CST to the male level and resulted in significant expression of both phases of morphine effect but did not abolish the sex difference in responsiveness to morphine. CONCLUSIONS: The biphasic modulation of seizure threshold is subject to both constitutive sex differences in sensitivity to morphine and hormonal fluctuations during the estrus cycle.     

Burn-induced red blood cell deformability and shape changes are modulated by sex hormones

BACKGROUND: Burns are known to cause changes in red blood cell (RBC) deformability and resting shape. However, it is unclear whether sex and sex hormones can influence the severity of these alterations. METHODS: Red blood cell deformability and shape were examined in proestrus and diestrus female rats, ovariectomized female rats, as well as castrated and non-castrated male rats (6 animals per group) subjected to scald burn. Red blood cell deformability was measured by laser ektacytometry and erythrocyte shape was evaluated by scanning electron microscopy. RESULTS: Burn-induced RBC deformability changes (decrease in elongation index) and shape alterations (increase in the percentage of reversibly and irreversibly changed cells) were less severe in proestrus females than in diestrus females or males. Ovariectomized rats demonstrated more severe RBC changes than non-ovariectomized ones. The degree of RBC damage was the same in castrated and non-castrated males. CONCLUSIONS: Removal of female sex hormones increases the severity of burn-induced RBC, indicating that female sex hormones protect against burn-induced RBC dysfunction. In contrast, male sex hormones do not appear to modulate burn-induced RBC dysfunction.     

Cannabinoid receptor antagonism increases female sexual motivation

The current experiments examined whether treatment with a CB1 antagonist/inverse agonist (AM251) affects sexual motivation, proceptivity, and receptivity in female rats. In experiment #1, 92 Long-Evans rats were tested for their socio-sexual motivation via a runway methodology. Motivation to approach and maintain close proximity to an empty goalbox, a female, and a male target was assessed following hormonal and drug treatment. Hormone treatments were: oil vehicle, 10 μg estradiol, and 10 μg estradiol + 500 μg progesterone. Drug doses were 0, 2, and 4 mg/kg AM251 (IP, 60 min prior to testing). In experiment #2, 32 female subjects were tested for receptivity and proceptivity in a paced mating chamber. Subjects were given either a high (10 μg estradiol + 500 μg progesterone) or low dose of hormones (2 μg estradiol + 250 μg progesterone), and either vehicle or 2 mg/kg AM251. AM251 significantly increased sexual motivation for a male target in the runway in females primed with both estradiol and progesterone. AM251 also enhanced lordosis (in low hormone females) and increased hop-darts. These findings suggest that endocannabinoids tonically inhibit estrous behaviors. Cannabinoid antagonists could serve as new treatment option for women suffering from abnormally low libido.