Increased synaptic input to gonadotropin-releasing hormone neurons in aged, virgin, male sprague-dawley rats

Using double-label ultrastructural immunocytochemistry, we found the synaptic input to gonadotropin-releasing hormone (GnRH) neurons in the preoptic area of aged (20 months old), virgin, male Sprague-Dawley rats to be denser than that in young adults (3 months old). These results confirmed earlier observations on F-344 virgin male rats. The aging F-344 rat, however, is prone to testicular tumor and so it was essential to see if the phenomenon was reproducible in another rat strain. In the first study, a portion of the increase in synaptic density was due to an increase in the proportion of synapses containing pleimorphic vesicles, frequently associated with the neurotransmitter GABA. We tested the possibility directly using a double-label protocol for GnRH and glutamic acid decarboxylase (GAD). However, in the present study the density of input by GABA did not change with age. This inhibitory amino acid represented about 10% of the total innervation in young animals; but, in aged animals, because the total synaptic input was greater, GABA represented only about 4% of the innervation. Synaptic vesicles within GAD-immunoreactive terminals were uniformly clear and spherical, suggesting that pleiomorphic vesicle shape is not an appropriate criterion for GABAergic innervation.     

Ultrastructural characterization of gonadotropin-releasing hormone (GnRH)-immunoreactive terminal nerve cells in the dwarf gourami

Recently we have been studying gonadotropin-releasing hormone (GnRH) cells of the terminal nerve (TN) in the dwarf gourami, which may serve as a good model system for the study of neuromodulator functions. Here we report on the ultrastructural characterization of TN-GnRH cells using postembedding immunoelectron microscopy. The GnRH immunoreactivities could be demonstrated on dense-cored vesicles (DCVs) in cell bodies, fibers and varicosities. However, we could find no evidence of GnRH-immunoreactive synapses which are characterized by active zones. This may suggest that GnRH is released non-synaptically from DCV-containing fiber varicosities and that it exerts its modulatory action on GnRH receptors located on nearby as well as distant target neurons.     

Hormonal regulation of brain circuits mediating male sexual behavior in birds

Male sexual behavior in both field and laboratory settings has been studied in birds since the 19th century. Birds are valuable for the investigation of the neuroendocrine mechanisms of sexual behavior, because their behavior can be studied in the context of a large amount of field data, well-defined neural circuits related to reproductive behavior have been described, and the avian neuroendocrine system exhibits many examples of marked plasticity. As is the case in other taxa, male sexual behavior in birds can be usefully divided into an appetitive phase consisting of variable behaviors (typically searching and courtship) that allow an individual to converge on a functional outcome, copulation (consummatory phase). Based primarily on experimental studies in ring doves and Japanese quail, it has been shown that testosterone of gonadal origin plays an important role in the activation of both of these aspects of male sexual behavior. Furthermore, the conversion of androgens, such as testosterone, in the brain to estrogens, such as 17beta-estradiol, is essential for the full expression of male-typical behaviors. The localization of sex steroid receptors and the enzyme aromatase in the brain, along with lesion, hormone implant and immediate early gene expression studies, has identified many neural sites related to the control of male behavior. The preoptic area (POA) is a key site for the integration of sensory inputs and the initiation of motor outputs. Furthermore, prominent connections between the POA and the periaqueductal gray (PAG) form a node that is regulated by steroid hormones, receive sensory inputs and send efferent projections to the brainstem and spinal cord that activate male sexual behaviors. The sensory inputs regulating avian male sexual responses, in contrast to most mammalian species, are primarily visual and auditory, so a future challenge will be to identify how these senses impinge on the POA-PAG circuit. Similarly, most avian species do not have an intromittent organ, so the projections from the POA-PAG to the brainstem and spinal cord that control sexual reflexes will be of particular interest to contrast with the well characterized rodent system. With this knowledge, general principles about the organization of male sexual circuits can be elucidated, and comparative studies relating known species variation in avian male sexual behaviors to variation in neural systems can be pursued.     

Tyrosine hydroxylase-immunoreactivity and its relations with gonadotropin-releasing hormone and neuropeptide Y in the preoptic area of the guinea pig

The present study examines the distribution of tyrosine hydroxylase (TH) immunoreactivity and its morphological relationships with neuropeptide Y (NPY)- and gonadoliberin (GnRH)-immunoreactive (IR) structures in the preoptic area (POA) of the male guinea pig. Tyrosine hydroxylase was expressed in relatively small population of perikarya and they were mostly observed in the periventricular preoptic nucleus and medial preoptic area. The tyrosine hydroxylase-immunoreactive (TH-IR) fibers were dispersed troughout the whole POA. The highest density of these fibers was observed in the median preoptic nucleus, however, in the periventricular preoptic nucleus and medial preoptic area they were only slightly less numerous. In the lateral preoptic area, the density of TH-IR fibers was moderate. Two morphological types of TH-IR fibers were distinguished: smooth and varicose. Double immunofluorescence staining showed that TH and GnRH overlapped in the guinea pig POA but they never coexisted in the same structures. TH-IR fibers often intersected with GnRH-IR structures and many of them touched the GnRH-IR perikarya or dendrites. NPY wchich was abundantly present in the POA only in fibers showed topographical proximity with TH-IR structures. Althoug TH-IR perikarya and fibers were often touched by NPY-IR fibers, colocalization of TH and NPY in the same structures was very rare. There was only a small population of fibers which contained both NPY and TH. In conclusion, the morphological evidence of contacts between TH- and GnRH-IR nerve structures may be the basis of catecholaminergic control of GnRH release in the preoptic area of the male guinea pig. Moreover, TH-IR neurons were conatcted by NPY-IR fibers and TH and NPY colocalized in some fibers, thus NPY may regulate catecholaminergic neurons in the POA.     

Telencephalic and preoptic areas integrate sexual behavior in hime salmon (landlocked red salmon, Oncorhynchus nerka): results of electrical brain stimulation experiments

Various patterns of sexual behavior were evoked in freely swimming hime salmon by electrical stimulation of specific loci in the telencephalon and the preoptic area (POA) using chronically implanted electrodes. Furthermore, co-ordinated sexual behavior corresponding to stages of the natural spawning sequence was elicited from some of these brain regions. These results suggest that (1) sexual behavior is integrated in specific parts of the telencephalon and POA, and (2) within these regions there is a hierarchy of neural systems which mediate progressively more complete components of normal sexual behavior.     

卵泡刺激素受体(FSHR32-44)肽疫苗对雄性小鼠生殖器官影响

目的探讨FSHR32-44肽疫苗对雄性小鼠的生殖器官及机能影响。方法 Balb/c雄性小鼠随机分FSHR32-44(20μg)组、FSHR32-44(80μg)组、FSHR140蛋白组及PBS组(对照组),用竞争性RIA法检测血睾酮水平、HE染色观察睾丸及附睾组织病理改变、硝酸镧示踪法观察血睾屏障的超微结构变化。结果 FSHR32-44(20μg)组、FSHR32-44(80μg)组、FSHR140蛋白组及PBS组(对照组)的血睾酮水平分别为(2.65±0.34)%、(2.63±0.25)%、(2.4±0.56)%及(2.7±0.28)%,肽组与对照组比较,睾酮水平变化无统计学差异(P>0.05);蛋白组与对照组比较,睾酮水平下降(P<0.05)。光镜下肽组及蛋白组中的睾丸及附睾精子数减少,但蛋白组中睾丸的精原细胞出现水肿及点状坏死;电镜下肽组的血睾屏障无损伤。结论 FSHR32-44肽疫苗免疫小鼠后,无论低剂量还是高剂量对生殖器官及性激素不产生任何影响。     

Effects of pelvic nerve and pudendal nerve transection on mating behavior in the male rat

The role of the pelvic nerves in mediating erection in the male rat was investigated. The frequency and duration of erections and other criteria of mating behavior were studied in a group of animals in which the pelvic nerves were bilaterally transected. Compared with the performances of sham-operated animals, no differences were obtained in 4 postoperative mating tests. It is concluded that erection in the rat is not mediated by the pelvic nerves. The effects of bilateral transection of the pudendal nerves upon mating behavior and the temporal patterning of this behavior were studied in adult male rats. It appeared that erection, intromission and ejaculation were prevented, while mounting behavior and the temporal patterning of the mating behavior were not affected. The results indicate that erection in the rat is mediated by the pudendal nerves. Moreover it is concluded that by means of pudendal nerve transection sexual motivation in the rat can be studied without the possible interference of intromissions, for a prolonged period.     

Orphanin FQ and glutamate connection in the regulation of gonadotropin-releasing hormone secretion in the preoptic area of conscious male rats

Utilizing the method of push-pull perfusion and radioimmunoassay (RIA), the secretory profile of gonadotropin-releasing hormone (GnRH) in the preoptic area (POA) and serum-luteinizing hormone (LH) levels were examined in conscious male rats after administration of [Nphe(1)]NC(1-13)NH(2), a competitive antagonists of the opioid receptor-like 1 receptor (ORL1 receptor) which is endogenous receptor for Orphanin FQ (OFQ). Glutamate release in the POA was also measured by high-performance liquid chromatography (HPLC) after perfusion of [Nphe(1)]NC(1-13)NH(2), i.e. NC13. The results showed that GnRH secretion from the POA and serum LH levels was increased significantly 40 min and 60 min, respectively after perfusion of 2 and 20 mmol/L NC13 in freely moving male rats (p<0.05). Pretreatment with a glutamate, N-methyl-D-aspartate (NMDA) receptor antagonist (MK-801, s.c., 0.2 mg/kg) abolished the increase of GnRH release in the POA induced by 2 mmol/L NC13. Additionally, 20 mmol/L NC13 significantly enhanced glutamate release in the POA at 40 min post-perfusion in a dose-dependent manner. These findings suggest that hypothalamic OFQ/ORL1 receptor system plays a role in the physiological inhibitory control of GnRH secretion in the POA of male rats, and provide evidence for involvement of an OFQ and glutamate pathway in the control of GnRH secretion.     

Interactional effects of pudendal nerve section and social restriction on male rat sexual behavior

Transection of the pudendal nerve causing desensitization of the glans penis impaired the sexual behavior of male rats. Compared to intact males, fewer animals performed intromissions and ejaculations while no decrease in mounting frequency was observed. The total sexual activity as measured by number of mounts and intromissions was decreased and the copulatory efficiency as measured by the ratio of intromissions and total sexual activity was lowered. The impairment of the sexual activity following penile desensitization was more marked in inexperienced rats than in experienced ones. It was concluded that penile stimulation, although not a prerequisite for any specific component of the mating pattern, still is necessary for maintaining the behavior at a normal performance level.     

浙江省台州地区167例男性不育的染色体畸变及生殖激素水平研究

目的研究男性不育与染色体畸变及生殖激素水平关系。方法对167例男性不育患者进行染色体核型分析和精液常规检测,用电化学发光法测定生殖激素水平。结果不育男性患者染色体异常发生率为10.8%(18/167),其中性染色体异常占7.2%(12/167),常染色体异常占3.6%(6/167)。染色体核型异常患者FSH、LH均不同程度升高,而T水平偏低;染色体核型正常无精子症组FSH、LH显著高于少弱精子症与对照组,少弱精子组也显著均高于对照组,另四项T、PRL、E2、P三组间不存在差异。结论染色体异常是造成男性不育重要因素,而生殖激素水平能反映不同程度的生精障碍,对男性不育者有必要进行细胞遗传学检查和生殖激素检测。     

Effect of sex steroids on the reproductive behavior of castrated male ring doves (Streptopelia sp.)

Castrated male ring doves were injected with 100 μg/day testosterone propionate (TP), estradiol benzoate (EB), or dihydrotestosterone propionate (DHTP) for two weeks and then tested for sexual and aggressive behavior with female partners. TP restored bow-cooing, hop-charging, wing-flipping, and copulation to levels of intact males. EB stimulated a great deal of wing-flipping, but little other behavior. DHTP stimulated some bow-cooing and hop-charging, but little wing-flipping or copulation. In a second experiment, DHTP again activated bow-cooing and hop-charging, but DHT (the free alcohol form of this steroid) was without significant effect. Thus, DHTP is behaviorally effective in this species, “aggressive” courtship and “nest-oriented” courtship have different patterns of steroid specificity, and wing-flipping in intact males may result from conversion of androgen to estrogen by the brain.