Immunocytochemical evidence for an NMDA1 receptor subunit in dissociated cells of Hydra vulgaris

Abstract

We have previously reported immunocytochemical, biochemical, behavioral, and electrophysiological evidence for glutamatergic transmission through (+/-)-alpha-amino-3-hydroxy-5-methyl-isoxazole-4-propionic acid (AMPA)/kainate receptors in hydra. We now report specific localization of the N-Methyl-D-aspartic acid receptor subunit 1 (NMDAR1) in epithelial, nerve, nematocytes, and interstitial cells of hydra. Macerates of tentacle/hypostome pieces of Hydra vulgaris were prepared on agar-coated slides, fixed with buffered formaldehyde/glutaraldehyde, and fluorescently labeled with monoclonal antibodies against mammalian NMDAR1. Negative controls omitted primary antibody. Digital images were recorded and analyzed. Specific localized and intense labeling was found in ectodermal battery cells, other epithelial cells, nematocytes, interstitial cells, and sensory and ganglionic nerve cells, and in battery cells was associated with enclosed nematocytes and neurons. The labeling of myonemes was more diffuse and less intense. In nerve and sensory cells, punctate labeling was prominent on cell bodies. These results are consistent with our earlier evidence for glutamatergic neurotransmission and kainate/NMDA regulation of stenotele discharge. They support other behavioral and biochemical evidence for a D-serine-sensitive, strychnine-insensitive, glycine receptor in hydra and suggest that the glutamatergic AMPA/kainate-NMDA system is an early evolved, phylogenetically old, behavioral control mechanism.

Chemosensory pathways in the capitate tentacles of the hydroid Cladonema

“…Furthermore, based on the appearance of vesicles in presynaptic neuro-cnidocyte, and neuro-neuro-cnidocyte synapses (Holtmann and Thurm 2001a;Westfall 2004) and various immunocytochemical studies (for review, see Scappaticci et al 2004), there are likely to be a variety of types of innervation, including a peptidergic component that is found in all classes of Cnidaria (Anderson et al 2004), and includes peptidergic sensory cells. Given that cnidocytes in isolated tentacles from Physalia (Purcell and Anderson 1995) and tentacular cells of Cladonema respond to chemical stimulants dissolved in the bathing sea water, it is possible that these peptidergic sensory cells, together with the peptidergic nerve nets to which they connect, are involved in at least some of the responses evoked by those stimulants, perhaps serving to prime the cnidocytes in advance of contact with the source of the chemical stimulant.…”

“…Holtmann and Thurm 2001a, b; West- fall 2004), histological(Anderson et al 2004; Kass-Si- mon and Scappaticci 2004;Scappaticci et al 2004), and…”

Molecular Characterization of NMDA-Like Receptors inAplysiaandLymnaea:Relevance to Memory Mechanisms

“…We would like to stress that the lingering controversy over the universality of the role of NMDA receptors as a key factor in learning and memory across different animal phyla, as well as over evolutionary aspects of functions for NMDA receptors (e.g., Wu, 2002;Rose et al, 2003) is primarily due to insufficient comparative data-especially data from basal metazoa (e.g., Pierobon et al, 2004;Scappaticci et al, 2004). Molecular and functional characterization of nonvertebrate homologs of these receptors would probably reveal novel regulatory mechanisms and pathways.…”

Putative NMDA receptors in Hydra: a biochemical and functional study

“…[ 3 H]glutamate binding was specific, saturable and reversible, and it was displaced by quisqualate, kainate and reduced glutathione (GSH), but not by NMDA. However, a recent immunocytochemical study reported specific localization of the NR1 subunit in dissociated neurons, nematocytes and epithelial cells of the hypostomal region, as well as in battery cells of tentacles in Hydra (Scappaticci et al ., 2004).…”