Immunohistochemical localization of RF-amide and GABA A receptors in the hypostome and tentacles of Hydra vulgaris

Jessica Eason, University of Rhode Island


This study examined the distribution and localization of the neuropeptide arginine phenylalanine-amide (RF-amide) and GABAA receptors in the hypostomal and tentacular nerve net of the cnidarian polyp Hydra vulgaris. Immunohistochemical techniques were used to visualize two distinct GABAA receptor- positive ring structures, nerves, neurites and epithelial cells as well as an RF-amide positive nerve ring, nerve cell bodies and neurites throughout the ectoderm of the hypostome and tentacles of ablated hypostomes. One GABAA receptor- positive ring, exclusively labeling ectodermal effector cells, in coincidence with an anti-α-tubulin- positive proximal nerve ring labeling nerve fibers as well as a GABA A receptor- positive ring, labeling nerve cell bodies and fibers, congruent with the anti-α-tubulin- positive distal nerve ring are reported here. GABAA receptors were also found on ectodermal effector and epithelial cells in the apex of the hypostome, in battery cell components in tentacles and at tentacle insertions suggesting involvement of GABAA receptors in both tentacle and contraction pulse control. RF-amide was identified in nerve fibers and nerve cell bodies of the proximal nerve ring and ubiquitously in bi-polar and tripolar nerve cells and fibers throughout the hypostome as well as in ganglion cells, sensory cells and neurites of the tentacle. This study provides evidence of the localized distribution of GABAARs in the nerves and effector cells of the hypostome of hydra and the wide distribution of RF-amide receptors in their neurites and cell bodies. It also provides the first evidence of an intimate association between RF-amide containing nerves and GABAA receptor effector and neuronal cells, suggesting their mutual interaction in the neuro-effector systems controlling hydra’s behavior.^

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Recommended Citation

Jessica Eason, "Immunohistochemical localization of RF-amide and GABA A receptors in the hypostome and tentacles of Hydra vulgaris" (2016). Dissertations and Master's Theses (Campus Access). Paper AAI10191229.