This review annotates and categorises the glia of adult and other

This review annotates and categorises the glia of adult and other model (-)-Gallocatechin gallate insects and describes the developmental origins of these in the optic lobe. but other than the antennal lobes these have not been described in detail. Surface glia form the blood brain barrier regulating the flow of (-)-Gallocatechin gallate substances into and out of the nervous system both for the brain as a whole and the optic neuropiles in particular. Cortex glia provide a second level of barrier wrapping axon fascicles and isolating neuronal cell bodies both from neighbouring brain regions and from their underlying neuropiles. Neuropile glia can be generated in the adult and a subtype ensheathing glia are responsible for cleaning up cellular debris during Wallerian degeneration. Both the neuropile ensheathing and astrocyte-like glia may be involved in clearing neurotransmitters from the extracellular space thus modifying the levels of histamine glutamate and possibly dopamine at the synapse to ultimately affect behaviour. (Ito pers. comm.). Various genetic markers for example expression of the genes ((nervous system and as a result glial cells are now easily PRKCZ distinguished from neurons in this species. Amongst glia themselves though even those with structural similarities such as the glia of the larval peripheral nervous system (PNS) can have distinct origins and genetic identities (von Hilchen or the honeybee makes this clearly the most propitious insect in which to analyse the functional roles of glia in the adult insect nervous system. These roles include not only their molecular functions but also the effects of glia on nervous system survival function and ultimately behaviour. 1.1 Types of glia Glia can be classified by their location their ultrastructure (Hoyle 1986 function or patterns of gene expression (Table 1). In flies such as or the housefly CNS 1.1 Surface glia Flattened surface glia constitute the externalmost layer of the blood brain barrier (BBB) that isolates the nervous system from the haemolymph of the insect’s open circulatory system. They are composed of two types of glia that can be distinguished by their location and cell shape: perineurial (apical) cells which are covered by a thick extracellular matrix the neural lamella and subperineurial (basal) glia. Perineurial glia lie on the ganglionic surface and have small elongate nuclei. These glia develop postembryonically in a non-GCM-dependent manner (Awasaki (2008) propose that these two glial cell layers with their differential patterns of gene expression play non-overlapping complementary roles in regulating the permeability of the BBB. There has been some question in the literature whether the immature perineurial cells of embryos are actually (-)-Gallocatechin gallate glia and not haemocytes (Pereanu early in their development (Hartenstein expressing glia which are developmentally delayed and which do inevitably express glial specific markers in the larva and early pupal stages (Awasaki is never expressed in GCM-positive haemocytes (Lee and Jones 2005 1.1 Cortex glia Cortex glia are embedded amongst and maintain close contact with the somata of neurons in the cortex of the CNS (Freeman and Doherty 2006 Anatomically they form a mesh in the cortex and one cortex (-)-Gallocatechin gallate glial cell can enwrap many neuronal cell bodies (Awasaki is essential for glial specification in (Jones glia express Neurexin a key junctional protein component required for vertebrate myelination (Baumgartner (Awasaki glia see Freeman and Doherty (2006). 2 Systems glia Glia can be further subdivided according to the neuropile with which they are associated and by the locations they occupy within that neuropile. 2.1 Optic lobe glia The glia of the fly’s visual system have several distinct morphological subtypes that have been described in extensive detail for the first optic neuropile (-)-Gallocatechin gallate or lamina (Fig. 1) of (Saint Marie and Carlson 1983 and the second optic neuropile or medulla and the associated chiasmata of the optic lobe in (Tix is composed of approximately 800 unit ommatidia each containing a fixed complement of cells. These include eight photoreceptor neurons as well as the pigment and cone support cells (Wolff and Ready 1993 Each photoreceptor axon terminates in one of three different strata of the optic lobe depending upon the opsin expression of its soma and thus its spectral sensitivity. Photoreceptors R1-R6 have axons that terminate in the lamina sorting at the distal face of the lamina so as to converge upon a unit (-)-Gallocatechin gallate column or cartridge along with other R1-R6 axons that signal the same point in visual space according to a principle of.