Sex steroids modulate the signals from volatile female odors in the accessory olfactory bulb of male mice

We previously reported that male mice detect volatile female odors via the accessory olfactory system, and that these odors activate granule cells in the accessory olfactory bulb (AOB) with a characteristic pattern. We also reported that sex steroids modulate the attraction of male mice to volatile female odors. The present study investigated hormonal modulation of signals from volatile female odors in the AOB with c-Fos immunostaining. After intact male mice were exposed to volatile female odors, there were more c-Fos positive cells in the caudal granule cell layer (GCL) than in the rostral GCL of the AOB. This effect was observed 3 days but not 7 days after castration, suggesting that hormonal deficiency causes the reorganization of the AOB after 3 days. There was no difference in the number of c-Fos positive cells between the rostral and caudal GCL of castrated male mice treated with 17 beta-estradiol (E). In contrast, there were more c-Fos positive cells in the caudal GCL than in the rostral GCL of castrated male mice treated with dihydrotestosterone (DHT). In both DHT- and E-treated castrated male mice, there was no difference in the number of c-Fos positive cells between the rostral GCL and caudal GCL. This finding suggests that E disrupts the effect of DHT, and that androgen is required for maintaining the intact neuronal network of the AOB. The present study suggests that sex steroids modulate the signals from volatile female odors in the AOB of male mice.     

The expression of the immediate-early genes c-fos, egr-1 and c-jun in the accessory olfactory bulb during the formation of an olfactory memory in mice.

Female mice form a memory for the pheromones of the male with which they mate. It has been proposed that the site of the synaptic changes underlying this memory is the accessory olfactory bulb, at the first level of the accessory olfactory system. In this study we have examined the expression of the immediate-early genes c-fos, c-jun and egr-1 in the mitral and granule cells of the accessory olfactory bulb immediately after mating, during the period of memory formation. Transient increases were seen in the number of granule cell nuclei expressing c-fos and the number of granule and mitral cell nuclei expressing egr-1, during the period of memory formation. No changes were observed in the expression of c-jun during this period. The increase in the number of cells expressing c-fos and egr-1 required the association of mating and pheromonal exposure, conditions also required for memory formation. Large increases in the number of mitral and granule cell nuclei expressing c-fos and egr-1 were also observed following the infusion of the drug bicuculline into the accessory olfactory bulb in the absence of mating. This procedure has previously been shown to result in the formation of a nonspecific memory for male pheromones. These results associate the expression of c-fos and egr-1 in the accessory olfactory bulb with the conditions required for the formation of an olfactory memory for male pheromones.     

Immunohistochemical and enzyme-histochemical study on the accessory olfactory bulb of the dog

The accessory olfactory bulb (AOB) is a primary center of the vomeronasal system. In the dog, the position and morphology of the AOB remained vague for a long time. Recently, the morphological characteristics of the dog AOB were demonstrated by means of lectin-histochemical, histological, and immunohistochemical staining, although the distribution of each kind of neuron, especially granule cells, remains controversial in the dog AOB. In the present study, we examined the distribution of neuronal elements in the dog AOB by means of immunohistochemical and enzyme-histochemical staining. Horizontal paraffin or frozen sections of the dog AOB were immunostained with antisera against protein gene product 9.5 (PGP 9.5), brain nitric oxide synthase (NOS), glutamic acid decarboxylase (GAD), tyrosine hydroxylase (TH), substance P (SP), and vasoactive intestinal polypeptide (VIP) by avidin-biotin peroxidase complex method. In addition, frozen sections were stained enzyme-histochemically for NADPH-diaphorase. In the dog AOB, vomeronasal nerve fibers, glomeruli, and mitral/ tufted cells were PGP 9.5-immunopositive. Mitral/ tufted cells were observed in the glomerular layer (GL) and the neuronal cell layer (NCL). In the NCL, a small number of NOS-, GAD-, and SP-immunopositive and NADPH-diaphorase positive granule cells were observed. In the GL, GAD-, TH-, and VIP-immunopositive periglomerular cells were observed. In the GL and the NCL, TH-, and VIP-immunopositive short axon cells were also observed. In addition to these neurons, TH- and SP-immunopositive afferent fibers were observed in the GL and the NCL. We could distinctly demonstrate the distribution of neuronal elements in the dog AOB. Since only a small number of granule cells were present in the dog AOB, the dog AOB did not display such a well-developed GCL as observed in the other mammals. Anat. Rec. 252:393–402, 1998. © 1998 Wiley-Liss, Inc.     

An experimental study of the projection of the amygdala to the accessory olfactory bulb and its relationship to the concept of a dual olfactory system

Summary The present anatomical findings point to the existence of a separate subdivision of the olfactory system whose connections are quite different from the principal part. The main olfactory bulb has olfactory afferents from the receptors of the general olfactory mucosa, while the accessory bulb has afferents from receptors in the vomeronasal organ. The main bulb projects to the olfactory tubercle and pyriform cortex, while the accessory bulb projects to the amygdala. In turn these areas are further related with the medial forebrain bundle in the case of the pyriform cortex and olfactory tubercle, and with the medial preoptic area and medial hypothalamus in the case of the amygdala. The main and accessory olfactory bulbs are further distinguished by their centrifugal connections, the main bulb receiving fibres from the olfactory tubercle passing through the lateral olfactory tract, and the accessory olfactory bulb receiving fibres from the amygdala through the stria terminalis. The centrifugals to the accessory olfactory bulb resemble those to the main bulb in that both appear to terminate upon granule cells, although further projections to the external plexiform layer or to the periglomerular region have not been demonstrated for the accessory bulb. By virtue of its neural connections the accessory olfactory system is ideally placed to mediate the effects of olfactory stimuli on reproduction.     

Oxytocin facilitates the induction of long-term potentiation in the accessory olfactory bulb

When female mice are mated, they form a memory to the pheromonal signal of their male partner. Several lines of evidence indicate that the neural changes underlying this memory occur in the accessory olfactory bulb (AOB) at the first stage of the vomeronasal system. The formation of this memory depends on the mating-induced release of noradrenaline in the AOB. In addition to noradrenaline, the neuropeptide oxytocin (OT) is also released within the central nervous system during mating. Because OT has been implicated in social memory and its receptors are expressed in the AOB, we hypothesized that OT might promote the strength of synaptic transmission from mitral to granule cells in the AOB. To test this hypothesis, we analyzed the lateral olfactory tract-evoked field potential that represents the granule cell response to mitral cell activation and its plasticity in parasagittal slices of the AOB. Of the 10-, 20-, 50-, and 100-Hz stimulations tested, the 100-Hz stimulation was optimal for inducing long-term potentiation (LTP). OT paired with 100-Hz stimulation that only produced short-term potentiation enhanced LTP induction in a dose-dependent manner. OT-paired LTP was blocked by both the selective OT antagonist desGly-NH₂,d(CH₂)₅[Tyr(Me)²,Thr⁴]-ornithine vasotocin and the N-methyl-d-aspartate (NMDA) receptor antagonist dl-2-amino-5-phosphonovaleric acid. These results indicate that OT can function as a gate to modulate the establishment of NMDA receptor-dependent LTP at the mitral-to-granule cell synapse in the AOB.     

Olfactory cues and accessory olfactory bulb lesion: effects on sexual behavior in the cyclic female rat

The influence of olfactory cues and accessory olfactory bulb (AOB) lesion on female sexual behavior was studied in virgin female Wistar rats. In Experiment 1, it appeared that distance or contact exposure to male urine soiled bedding for 8 hours before testing increased sexual receptivity, i.e., the number of receptive females at 18:00-19:00 on proestrus. In Experiment 2, we observed that sexual receptivity at 18:00-19:00 on proestrus was not affected by AOB lesion as compared to sham-operated females. In Experiment 3 the effects of both AOB lesion and olfactory cues were analyzed. Sexual receptivity at 18:00-19:00 on proestrus did not significantly differ in sham-operated and accessory olfactory bulbectomized females both exposed to the odor of male urine. Regarding lordosis quotient in the three experiments, no significant difference was observed. Mechanisms whereby olfactory cues and/or AOB lesion modified female sexual behavior on proestrus in virgin female rats were discussed in the light of previous and present observations.     

小鼠嗅球中水通道蛋白4表达缺失对抑郁发生的影响

目的:观察水通道蛋白4(AQP4)在小鼠嗅球中的表达情况,探讨AQP4表达缺失对小鼠抑郁发生的影响。方法:应用免疫荧光技术观察小鼠嗅上皮和嗅球中AQP4的表达,采用嗅觉电位(EOG)测定比较小鼠的嗅觉差异,悬尾试验(TST)和喷溅试验(ST)检测AQP4基因敲除(AQP4^-/-)小鼠与野生型(WT)小鼠的抑郁样行为,并分析抑郁行为与嗅觉电位的相关性。结果:免疫荧光检测发现AQP4在嗅上皮和嗅球神经纤维层和突触小球层均有不同程度表达; AQP4^-/-与WT小鼠相比,食物性嗅觉电位诱发实验的电位更低(P <0.01);抑郁行为学发现AQP4^-/-小鼠悬尾实验的不动时间较长、第一次梳理背部毛发潜伏时间较长以及梳理时间较短(P <0.01); AQP4^-/-小鼠嗅觉电位与悬尾不动时间、梳理潜伏时间呈负相关(P <0.05),与梳理背部毛发时间呈正相关性(P <0.05)。结论:AQP4表达在小鼠嗅鞘细胞膜上,其表达对于维持嗅觉信号的传递具有重要意义,AQP4基因敲除引起小鼠嗅觉的减退...     

Estrogen-induced region specific decrease in the density of 5-bromo-2-deoxyuridine-labeled cells in the olfactory bulb of adult female rats

Effects of chronic estrogen treatment on the survival rate of newly integrated interneurons were studied in the olfactory bulb of adult (250-300 g) female rats. Ovariectomized rats received 17-beta estradiol dissolved in sesame oil (i.p., 100 microg/100 g body weight [b.w.]) during six consecutive days, and on day 6 they were also injected with the mitotic marker 5-bromo-2-deoxyuridine (BrdU, i.p., 50 mg/kg b.w.) in every 2 hours during 8 hours. After 21 days of survival animals were killed and the density of BrdU-immunoreactive cells was analyzed in the granule cell and glomerular layer both in the main and accessory olfactory bulb. A significant decrease was found in the density of BrdU-labeled cells in both layers examined in the accessory olfactory bulb of ovariectomized and estradiol-treated rats when compared with those of ovariectomized and vehicle-treated animals. In the main olfactory bulb, in contrast, no difference was observed in the density of BrdU-immunoreactive cells in either of the two layers. Our results suggest that cells destined to the glomerular and granule cell layers react in the same way to chronic estrogen treatment, and the effect of estradiol is region specific, at least, within the olfactory bulb. 17-Beta estradiol reduces the density of newly generated cells in the accessory olfactory bulb, an area involved in the perception of pheromones, thus having a role in regulating sexual behavior, while the rate of integration and survival of newly born cells in the first relay station of the main olfactory pathway, i.e. the main olfactory bulb, remains unchanged.     

Expression and regulation of the immediate-early gene product Arc in the accessory olfactory bulb after mating in male rat

Recent studies of the accessory olfactory bulb have shown that the expression of immediate-early genes, e.g., c-fos, c-jun and egr-1, can be used as a marker of neuronal activity in response to pheromonal cues. In this study, we analyzed the expression pattern, in response to mating, of the novel immediate-early gene product Arc (an activity-regulated cytoskeleton-associated protein). Arc is hypothesized to play a role in activity-dependent neuronal plasticity in the hippocampus. In a control group of male rats, only a small number of Arc-immunoreactive cells were observed in the accessory olfactory bulb. In a mating group, however, a marked increase in the number of Arc-immunoreactive cells was observed only in the granule cell layer of the accessory olfactory bulb. The increase in the number of Arc-immunoreactive cells after mating was similar to that observed for other immediate-early genes. However, for the mating group, the increase in Arc-positive cells was limited to the granule cell layer. Granule cells have been shown to exhibit a strong synaptic plasticity in response to pheromonal stimulation.From these findings we suggest that Arc plays an important role in neuronal plasticity in the accessory olfactory bulb.     

Electrophysiological studies of the tongue and accessory olfactory bulb in garter snakes

Tongue flicking in snakes transports environmental chemicals to the vomeronasal (Jacobson's) organ (VNO) which acts as a chemoreceptor. This paper provides the first electrophysiological evidence that the vomeronasal/accessory-olfactory system is activated following tongue flick. In acute experiments with partially anesthetized snakes, single units recorded in the accessory olfactory bulb (AOB) failed to show changes in firing rate following tongue flicks but changes in AOB activity did occur when cotton swabs soaked in prey extract were pressed to the roof of the mouth (where the VNO ducts open). In chronic experiments, multiunit recordings from electrodes implanted in the AOB of freely moving animals did reveal changes in neural activity following tongue flicks. EMG recordings from the hyoglossus (tongue retractor) muscle (and in one animal from the genioglossus [tongue extender] as well) were used to indicate precisely the time of tongue flicking. The techniques used in these experiments are detailed.     

小鼠出生后嗅球发育的基因表达差异及其特征分析

目的:通过研究小鼠嗅球全基因表达差异来寻找嗅球生后发育基因变化及其特征,为嗅球发育及相关研究提供参考依据。方法:分别取新生及成年野生型小鼠完整嗅球并独立进行RNA-seq分析,对全基因测序结果进行差异表达分析并通过检测成年与新生小鼠嗅球中差异表达基因(DEGs),利用Gene Ontology、DAVID及KEGG等数据库,结合q PCR的实验方法对部分差异表达基因进行验证,进一步分析差异表达基因在生物学上的影响。结果:成年小鼠和新生小鼠嗅球存在大量差异表达基因,其中Tfap2e,Neurod6和Tbr1等基因表达下调,同时Zfp365,Elt4以及Omp等基因表达上调,DEGs参与多种信号通路。结论:小鼠嗅球在出生后仍然处于不断发育的过程当中,这些差异表达基因主要影响细胞内代谢,细胞的分裂、分化、成熟及细胞间信号传递。     

Effect of bilateral accessory olfactory bulb lesions on volatile urinary odor discrimination and investigation as well as mating behavior in male mice

Previous research raises the possibility that urinary volatiles from estrous female mice activate mitral cells in the accessory olfactory bulb (AOB) of male mice following detection via the main olfactory epithelium as opposed to the vomeronasal organ. We asked whether bilateral lesions of the AOB would disrupt the ability of male mice to discriminate between urinary volatiles from mice of different sexes or endocrine states, or affect their interest in investigating these odors when they were presented sequentially in home-cage habituation/dishabituation tests. Males with either partial or complete bilateral lesions of the AOB resembled sham-operated control males in their ability to discriminate between ovariectomized and estrous female urinary volatiles as well as between male and estrous female urinary volatiles. However, males with either complete or partial AOB lesions spent significantly less time than sham-operated control males investigating urinary volatiles from estrous females, especially during tests when the alternative stimulus presented was male urine. Placement of AOB lesions failed to disrupt males' mating performance. Our results suggest that the incentive value of opposite-sex (female) volatile urinary odors which are initially detected by the main olfactory system is enhanced when they are further processed by the male's AOB.     

Somatostatin-14-like immunoreactive neurons and fibres in the human olfactory bulb

Summary This study describes the morphological features and the distribution pattern of neurons in the human olfactory bulb which are immunoreactive for an antiserum against the neuropeptide somatostatin-14.Immunoreactive nerve cell bodies were mainly found in the white matter surrounding the cell clusters of the anterior olfactory nucleus. Some immunoreactive neurons were also found scattered throughout the anterior olfactory nucleus and the deeper parts of the inner granule cell layer. Only a few immunoreactive neurons were localized in the glomerular layer and the outer granule cell layer.Immunoreactive fibres were found in all layers of the olfactory bulb. In addition, an impressive number of coiled and kinked immunoreactive fibres were localized within the anterior olfactory nucleus forming a dense plexus. Accumulations of twisted and coiled branches of immunoreactive fibres were rarely found either surrounding or within the olfactory glomerula.The characteristics of somatostatin-14 immunoreactive neurons as seen in the combined pigment-Nissl preparation were studied after decolourizing the chromogen and restaining the preparations with aldehydefuchsin in order to demonstrate the lipofuscin pigment and gallocyanin chrome alum for Nissl material. About 90% of the immunoreactive neurons studied in this manner turned out to be devoid of lipofuscin granules. The remaining 10% displayed different patterns of pigmentation.These findings suggest the presence of different types of somatostatin-14-like immunoreactive neurons in the olfactory bulb of the human adult.     

Proteinase-activated receptors 1 and 2 in rat olfactory system: layer-specific regulation of multiple signaling pathways in the main olfactory bulb and induction of neurite retraction in olfactory sensory neurons

Proteinase-activated receptors (PARs) are a family of four G protein-coupled receptors that are widely distributed in the CNS and involved in neural cell proliferation, differentiation and survival. The olfactory system undergoes continuous neurogenesis throughout life and may represent a critical target of PAR cellular actions. In the present study we investigated the functional activity of PAR1 and PAR2 in microdissected tissue preparations of olfactory nerve-glomerular layer (ON-GL), external plexiform layer (EPL) and granule cell layer (GRL) of the rat main olfactory bulb and in primary cultures of olfactory neuroepithelial cells. Activation of either PAR1 or PAR2 regulated multiple signaling pathways, including activation of pertussis-toxin sensitive Gi/o proteins, inhibition of cyclic AMP formation, stimulation of Gq/11-mediated phosphoinositide (PI) hydrolysis, phosphorylation of Ca2+/calmodulin-dependent protein kinase II and activation of the monomeric G protein Rho, predominantly in ON-GL, whereas only activation of Rho was detected in the deeper layers. Olfactory nerve lesion by nasal irrigation with ZnSO4 induced a marked decrease of PAR signaling in ON-GL. In primary cultures of olfactory neurons, double immunofluorescence analysis showed the localization of PAR1 and PAR2 in cells positive for olfactory-marker protein and neuron-specific enolase. Cell exposure to either nanomolar concentrations of thrombin and trypsin or PAR-activating peptides caused rapid neurite retraction. This study provides the first characterization of the laminar distribution of PAR1 and PAR2 signaling in rat olfactory bulb, demonstrates the presence of the receptors in olfactory sensory neurons and suggests a role of PARs in olfactory sensory neuron neuritogenesis.