Social avoidance behavior in male tree shrews and prosocial behavior in male mice toward unfamiliar conspecifics in the laboratory

Adult male tree shrews vigorously defend against intruding male conspecifics. However, the characteristics of social behavior have not been entirely explored in these males. In this study, male wild-type tree shrews(Tupaia belangeri chinensis)and C57 BL/6 J mice were first allowed to familiarize themselves with an open-field apparatus. The tree shrews exhibited a short duration of movement(moving) in the novel environment, whereas the mice exhibited a long duration of movement. In the 30 min social preference-avoidance test, target animals significantly decreased the time spent by the experimental tree shrews in the social interaction(SI)zone, whereas experimental male mice exhibited the opposite. In addition, experimental tree shrews displayed a significantly longer latency to enter the SI zone in the second 15 min session(targetpresent) than in the first 15 min session(targetabsent), which was different from that found in mice.Distinct behavioral patterns in response to a conspecific male were also observed in male tree shrews and mice in the first, second, and third 5 min periods. Thus, social behaviors in tree shrews and mice appeared to be time dependent. In summary,our study provides results of a modified social preference-avoidance test designed for the assessment of social behavior in tree shrews. Our findings demonstrate the existence of social avoidance behavior in male tree shrews and prosocial behavior in male mice toward unfamiliar conspecifics. The tree shrew may be a new animal model, which differs from mice, for the study of social avoidance and prosocial behaviors.

Atlas of the Striatum and Globus Pallidus in the Tree Shrew: Comparison with Rat and Mouse

The striatum and globus pallidus are principal nuclei of the basal ganglia. Nissl-and acetylcholinesterasestained sections of the tree shrew brain showed the neuroanatomical features of the caudate nucleus（Cd）,internal capsule（ic）, putamen（Pu）, accumbens, internal globus pallidus, and external globus pallidus. The ic separated the dorsal striatum into the Cd and Pu in the tree shrew, but not in rats and mice. In addition, computerbased 3 D images allowed a better understanding of the position and orientation of these structures. These data provided a large-scale atlas of the striatum and globus pallidus in the coronal, sagittal, and horizontal planes, the first detailed distribution of parvalbumin-immunoreactive cells in the tree shrew, and the differences in morphological characteristics and density of parvalbumin-immunoreactive neurons between tree shrew and rat. Our findings support the tree shrew as a potential model for human striatal disorders.

Lambda-cyhalothrin disrupts the up-regulation effect of 17β-estradiol on post-synaptic density 95 protein expression via estrogen receptor α-dependent Akt pathway

Lambda-cyhalothrin（LCT）,one of the type II pyrethroids,has been widely used throughout the world.The estrogenic effect of LCT to increase cell proliferation has been well established.However,whether the estrogenic effect of LCT will influence neurodevelopment has not been investigated.In addition,17β-Estradiol（E2）plays a crucial role in neurodevelopment and induces an increase in synaptic proteins.The post-synaptic density 95（PSD95）protein,which is involved in the development of the structure and function of new spines and localized with estrogen receptor α（ERα）at the post-synaptic density（PSD）,was detected in our study by using hippocampal neuron cell line HT22.We found that LCT up-regulated PSD95 and ERα expression,estrogen receptor（ER）antagonist ICI182,780 and phosphatidylinositol-4;5-bisphosphate 3-kinase（PI3K）inhibitor LY294,002 blocked this effect.In addition,LCT disrupted the promotion effect of E2 on PSD95.To investigate whether the observed changes are caused by ERα-dependent signaling activation,we next detected the effects of LCT on the ERα-mediated PI3K-Protein kinase B（PKB/Akt）-eukaryotic initiation factor（e IF）4E-binding protein 1（4E-BP1）pathway.There existed an activation of Akt and the downstream factor 4E-BP1 after LCT treatment.In addition,LCT could disrupt the activation effect of E2 on the Akt pathway.However,no changes in c AMP response element-binding protein（CREB）activation and PSD95 messenger ribonucleic acid（m RNA）were observed.Our findings demonstrated that LCT could increase the PSD95 protein level via the ERα-dependent Akt pathway,and LCT might disrupt the up-regulation effect of E2 on PSD95 protein expression via this signaling pathway.