Glutamatergic and GABAnergic control in the tentacle effector systems of Hydra vulgaris

Cloning and functional expression of voltage-gated ion channel subunits from cnidocytes of the Portuguese Man O'War Physalia physalis

“…There was no significant difference in the rate of inactivation under the two conditions. pathway composed of sensory cells (Holtmann and Thurm, 2001;Westfall, 2004), neurons (Kass-Simon andScappaticci, Jr, 2004;Price and Anderson, 2006) and in some instances, supporting cells (Watson and Roberts, 1995). One consequence of the fact that multiple cell types are involved in the regulation of discharge has been the challenge of localizing the site of action of some experimental manipulations.…”

“…Because of the complexity of the cell, and the fact that a cnidocyte can be used only once, their discharge is very tightly regulated to minimize what is likely to be the considerable energetic cost of replacement. Studies of the regulation of cnidocyte discharge have employed a variety of physiological (Gitter et al, 1994;Brinkmann et al, 1995;Purcell and Anderson, 1995;Salleo et al, 1996), structural (Lubbock et al, 1981;Westfall and Grimmelikhuijzen, 1993;Westfall, 2004) and histochemical approaches (Anderson et al, 2004;Kass-Simon and Scappaticci, Jr, 2004), using representatives of all cnidarian classes. Given that cnidocyte discharge is thought to be an exocytotic event, special attention (Lubbock et al, 1981;Gitter and Thurm, 1993;Gitter et al, 1994) has been given to the potential role of voltage-gated ionic currents, particularly Ca 2+ currents of the type that trigger exocytosis at synapses and exocrine cells (Sudhof, 2004).…”

“…Furthermore, because electrically induced discharge of Hydra cnidocytes is abolished in the absence of external Ca 2+ (Gitter et al, 1994), it has been proposed that voltage-gated Ca 2+ channels at the apical end of the cnidocyte are involved. However, although neurons are not always required for cnidocyte discharge (Aerne et al, 1991), cnidocytes are innervated by peptidergic (Anderson et al, 2004) and other classes of neuron (Kass-Simon and Scappaticci, Jr, 2004). Consequently, the effects of Ca 2+ -free media and Ca 2+ channel blockers could be manifest through their block of synaptic activity within the nerve nets that surround cnidocytes (Anderson et al, 2004;Price and Anderson, 2006), or at the level of synapses onto the cnidocytes themselves.…”

Hydrozoan nematocytes send and receive synaptic signals induced by mechano-chemical stimuli

“…Electron microscopy revealed afferent and efferent synaptic structures located basally at the nematocytes and separated from the surface medium by septate junctions, known as diffusion barriers (Holtmann and Thurm, 2001a;Holtmann and Thurm, 2001b). Histochemical identification of glutamate receptors at nematocytes has been reported (Kass- Simon and Scappaticci, 2004;Kass-Simon and Pierobon, 2007).…”

Evolution of neurotransmitter gamma-aminobutyric acid, glutamate and their receptors

“…The phylogenetic tree in Figure 3 shows the relationship among mGlu receptors (mGluR1-mGluR8), GABA B receptors (GABA B1 and GABA B2 ), and their ancestor homolog leucine-binding protein (LBP), a kind of PBP. The GABA B receptor can be found in Drosophila (Mezler et al, 2001), nematodes (Bargmann, 1998), and hydra (Kass-Simon et al, 2003;Kass-Simon & Scappaticci, 2004), suggesting that GABA B receptors may have existed before these species diverged. In more primitive animal porifera there is a protein highly homologous to the GABA B R1 receptor and mGluR5 receptor in rats.…”