NeuroNexus (United States)

Restoring function to injured axons requires not only regeneration, but also accurate guidance and synapse reformation. Our understanding of how regenerating axons navigate the mature nervous system remains limited, as growth cones confront a cellular and molecular landscape distinct from development. Using Caenorhabditis elegans , we found that the basement membrane protein Nidogen (NID-1) promotes local guidance of regenerating motor axons in the mature nervous system by facilitating their growth alongside neighboring intact neuronal processes. Regenerating cholinergic axons preferentially track the branched dendrites of the PVD mechanosensory neuron or, in the absence of PVD dendrites, are guided alongside GABAergic commissures instead. Loss of nid-1 disrupts this guidance, reducing axon-PVD colocalization, increasing displacement from the pre-injury point of contact with the dorsal nerve cord, and disrupting synapse reformation and functional recovery. Tissue-specific rescue indicates that NID-1 expressed by body wall muscles or the hypodermis is sufficient to guide regenerating axons, whereas muscle-derived NID-1 is required to restore synapse reformation. Genetic data indicate that NID-1 function guides regenerating axons in coordination with laminin and integrin. Although this complex primarily directs cholinergic motor axons, ectopic integrin expression in GABAergic neurons is sufficient to reroute their regenerating axons alongside PVD dendrites in a NID-1-dependent manner. Together, these findings identify a NID-1-dependent post-developmental mechanism for directing regenerating axons and promoting functional repair.

It has been 50 years since the suprachiasmatic nucleus (SCN) was first identified as the central circadian clock and 25 years since the last overview of developments in the field was published in the Journal of Biological Rhythms. Here, we explore new mechanisms and concepts that have emerged in the subsequent 25 years. Since 1997, methodological developments, such as luminescent and fluorescent reporter techniques, have revealed intricate relationships between cellular and network-level mechanisms. In particular, specific neuropeptides such as arginine vasopressin, vasoactive intestinal peptide, and gastrin-releasing peptide have been identified as key players in the synchronization of cellular circadian rhythms within the SCN. The discovery of multiple oscillators governing behavioral and physiological rhythms has significantly advanced our understanding of the circadian clock. The interaction between neurons and glial cells has been found to play a crucial role in regulating these circadian rhythms within the SCN. Furthermore, the properties of the SCN network vary across ontogenetic stages. The application of cell type-specific genetic manipulations has revealed components of the functional input-output system of the SCN and their correlation with physiological functions. This review concludes with the high-risk effort of identifying open questions and challenges that lie ahead.

The combination of optical stimulation and electrical recording is commonly employed in neuroscience research. Researchers using optogenetics are familiar with the photo-induced "artifacts" that arise from illumination of an electrode array. We sought to characterize this photoelectrochemical (PEC) effect to understand the underlying mechanism seen on NeuroNexus optoelectrodes. In doing so, we discovered that the phenomenon is inversely proportional to electrode site area in the same manner as electrical impedance measurements. We have applied the PEC effect as a method of electrode evaluation and show that a PEC measurement system can be both faster and more effective than impedance at sensing defects in high-throughput biomedical device testing.

The success of long-term electrophysiological recordings often depends on the quality of the implantation surgery. Here we provide useful information for surgeons who are learning the process of implanting electrode systems. We demonstrate the implantation procedure of both a penetrating and a surface electrode. The surgical process is described from start to finish, including detailed descriptions of each step throughout the procedure. It should also be noted that this video guide is focused towards procedures conducted in rodent models and other small animal models. Modifications of the described procedures are feasible for other animal models.