An experience-driven increase in oligodendrocytes and myelin in the somatosensory cortex (S1) has emerged as a new marker of adult cortical plasticity. That finding contrasts with the view that myelin is a structural brake on plasticity, and that contributes to ending the critical period (CP) in the visual cortex (V1). Despite the evidence that myelin-derived signaling acts to end CP in V1, there is no information about myelin changes during adult plasticity in V1. To address this, we quantified the effect of three manipulations that drive adult plasticity (monocular deprivation (MD), fluoxetine treatment or the combination of MD and fluoxetine) on the expression of myelin basic protein (MBP) in adult rat V1. In tandem, we validated that environmental enrichment (EE) increased cortical myelin by measuring MBP in adult S1. For comparison with the MBP measurements, three plasticity markers were also quantified, the spine markers drebrin E and drebrin A, and a plasticity maintenance marker Ube3A. First, we confirmed that EE increased MBP in S1. Next, that expression of the plasticity markers was affected in S1 by EE and in V1 by the visual manipulations. Finally, we found that after adult MD, MBP increased in the non-deprived V1 hemisphere, but it decreased in the deprived hemisphere, and those changes were not influenced by fluoxetine. Together, the findings suggest that modulation of myelin expression in adult V1 may reflect the levels of visually driven activity rather than synaptic plasticity caused by adult plasticity.

Glial cells are essential for the proper development and functioning of the peripheral nervous system (PNS). The ability to study the biology of glial cells is therefore critical for our ability to understand PNS biology and address PNS maladies. The genetic and proteomic pathways underlying vertebrate peripheral glial biology are understandably complex, with many layers of redundancy making it sometimes difficult to study certain facets of PNS biology. Fortunately, many aspects of vertebrate peripheral glial biology are conserved with those of the fruit fly,Drosophila melanogaster. With simple and powerful genetic tools and fast generation times,Drosophilapresents an accessible and versatile model for studying the biology of peripheral glia. We introduce here three techniques for studying the cell biology of peripheral glia ofDrosophilathird-instar larvae. With fine dissection tools and common laboratory reagents, third-instar larvae can be dissected, with extraneous tissues removed, revealing the central nervous system (CNS) and PNS to be processed using a standard immunolabeling protocol. To improve the resolution of peripheral nerves in thez-plane, we describe a cryosectioning method to achieve 10- to 20-µm thick coronal sections of whole larvae, which can then be immunolabeled using a modified version of standard immunolabeling techniques. Finally, we describe a proximity ligation assay (PLA) for detecting close proximity between two proteins—thus inferring protein interaction—in vivo in third-instar larvae. These methods, further described in our associated protocols, can be used to improve our understanding ofDrosophilaperipheral glia biology, and thus our understanding of PNS biology.

The ability to visualize the cells and proteins of a tissue within their original context (i.e., in vivo) is invaluable for the study of that biological system. Visualization is especially important in tissues with complex and convoluted structures, such as the neurons and glia of the nervous system. The central and peripheral nervous systems (CNS and PNS, respectively) of the third-instar larvae of the fruit fly,Drosophila melanogaster, are found on the ventral side of the larvae and are overlaid by the rest of the body tissues. Careful removal of overlying tissues while not damaging the delicate structures of the CNS and PNS is essential for proper visualization of these tissues. This protocol describes the dissection ofDrosophilathird-instar larvae into fillets and their subsequent immunolabeling to visualize endogenously tagged or antibody-labeled proteins and tissues in the fly CNS and PNS.