Isolation of the Brain Secretome from Ex Vivo Brain Slice Cultures.

The brain secretome consists of proteins either actively secreted or shed from the cell surface by proteolytic cleavage in the extracellular matrix of the nervous system. These proteins include growth factor receptors and transmembrane proteins, among others, covering a broad spectrum of roles in the development and normal functioning of the central nervous system. The current procedure to extract the secretome from cerebrospinal fluid is complicated and time-consuming, and it is difficult to isolate these proteins from experimental animal brains. In this study, we present a novel protocol for isolating the brain secretome from mouse brain slice cultures. First, the brains were isolated, sliced, and cultured ex vivo. The culture medium was then filtered and concentrated for isolating proteins by centrifugation after a few days. Finally, the isolated proteins were resolved using sodium dodecyl-sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and subsequently probed for purity characterization by western blot. This isolation procedure of the brain secretome from ex vivo brain slice cultures can be used to investigate the effects of the secretome on a variety of neurodevelopmental diseases, such as autism spectrum disorders.

TCB-2, a 5-hydroxytryptamine 2A receptor agonist, disrupts prepulse inhibition in the ventral pallidum and nucleus accumbens.

The 5-hydroxytryptamine 2A (5-HT2A) receptor plays an important role in schizophrenia. The 5-HT2A receptor is also involved in the regulation of prepulse inhibition (PPI) in rodents. The aim of this study was to determine whether selective 5-HT2A receptor agonizts or antagonists may alter PPI in rats and to identify the critical brain regions in which the activity of 5-HT2A receptors regulates PPI. The results showed that infusion of the 5-HT2A receptor agonist TCB-2 into the lateral ventricle disrupted PPI, but the 5-HT2A receptor antagonist M100907 had no such effect. In addition, local infusion of TCB-2 into the nucleus accumbens and ventral pallidum disrupted PPI, whereas the same manipulation in the medial prefrontal cortex, ventral hippocampus, and ventral tegmental area did not disrupt PPI. In conclusion, agonism of 5-HT2A receptors in the ventral pallidum and nucleus accumbens can disrupt PPI. The ventral pallidum and nucleus accumbens are critical brain regions responsible for the regulation of PPI by serotonin. These findings contribute to the extensive exploration of the molecular and neural mechanisms underlying the regulatory effect of 5-HT2A receptor activity on PPI, especially the neural circuits modulated by 5-HT2A receptor activity.

Expression and structural analysis of human neuroligin 2 and neuroligin 3 implicated in autism spectrum disorders.

The development of autism spectrum disorders (ASDs) involves both environmental factors such as maternal diabetes and genetic factors such as neuroligins (NLGNs). NLGN2 and NLGN3 are two members of NLGNs with distinct distributions and functions in synapse development and plasticity. The relationship between maternal diabetes and NLGNs, and the distinct working mechanisms of different NLGNs currently remain unclear. Here, we first analyzed the expression levels of NLGN2 and NLGN3 in a streptozotocin-induced ASD mouse model and different brain regions to reveal their differences and similarities. Then, cryogenic electron microscopy (cryo-EM) structures of human NLGN2 and NLGN3 were determined. The overall structures are similar to their homologs in previous reports. However, structural comparisons revealed the relative rotations of two protomers in the homodimers of NLGN2 and NLGN3. Taken together with the previously reported NLGN2-MDGA1 complex, we speculate that the distinct assembly adopted by NLGN2 and NLGN3 may affect their interactions with MDGAs. Our results provide structural insights into the potential distinct mechanisms of NLGN2 and NLGN3 implicated in the development of ASD.

MK212, a 5-hydroxytryptamine 2C receptor agonist, reverses prepulse inhibition deficits in the medial prefrontal cortex and ventral hippocampus.

Prepulse inhibition (PPI) is disrupted in many neuropsychiatric diseases. Molecules such as 5-HT2C receptor agonists alleviate PPI deficits in rodents; however, the precise mechanisms and critical regions of the brain responsible for the reversal effect of these agonists remain inconclusive. The present study aimed to investigate the areas of the brain critical for the reversal effect of 5-HT2C receptor agonists on PPI deficits in mice. The results showed that systemic administration of the 5-HT2C receptor agonist MK212 did not affect normal PPI behavior, but reversed the PPI deficits induced by the N-methyl d-aspartate receptor antagonist MK801 in mice. In addition, the 5-HT2C receptor antagonist SB242084 had no effect on PPI behavior despite MK801 treatment. Moreover, local infusion of MK212 into the medial prefrontal cortex and ventral hippocampus, excluding the nucleus accumbens or ventral tegmental area, rescued the PPI deficits induced by MK801. These data suggest that the medial prefrontal cortex and ventral hippocampus are critical brain areas responsible for the reversal of 5-HT2C agonists on PPI deficits. The results will contribute to our current knowledge on the molecular and neural mechanisms underlying the antipsychotic effects of 5-HT2C receptor agonists, especially the neural circuits modulated by 5-HT2C receptor activity.

Pimavanserin, a 5-hydroxytryptamine 2A receptor inverse agonist, reverses prepulse inhibition deficits in the nucleus accumbens and ventral hippocampus.

Prepulse inhibition (PPI) is disrupted in many neuropsychiatric diseases. Although the inverse agonist of the 5-hydroxytryptamine 2A (5-HT2A) receptors, pimavanserin, alleviates PPI deficits in rodents, the precise mechanisms and critical brain areas in the reversal effect of 5-HT2A receptor inverse agonists remain unclear. The present study aimed to investigate the critical brain areas responsible for the reversal effect of the 5-HT2A receptor inverse agonist on PPI deficits in male mice. The results showed that intraperitoneal administration of pimavanserin was found to improve normal PPI behavior and reverse PPI deficits elicited by the dopamine D1/D2 receptor nonselective agonist, pergolide. Further, local infusion of pimavanserin into the nucleus accumbens and ventral hippocampus reversed PPI deficits, whereas the same manipulation in the medial prefrontal cortex or ventral tegmental area did not reverse PPI deficits. Overall, the nucleus accumbens and ventral hippocampus are the critical brain areas responsible for the reversal effect of 5-HT2A inverse agonists on PPI deficits. Such findings contribute to the extensive exploration of the accurate molecular and neural mechanisms underlying the antipsychotic effects of 5-HT2A receptor inverse agonists, especially the neural circuits modulated by 5-HT2A receptor activity.