Regional modulation of the response to glutathione in Hydra vulgaris (Pallas, 1766).

Abstract

In the presence of prey, or upon exposure to reduced glutathione (GSH), Hydra polyps open a mouth to ingest the captured prey and close it after feeding; at rest the mouth is not evident. In previous papers we have shown that GABA, glycine and NMDA modulate the mechanisms of mouth closure through ligand-gated-ion-channel receptors that are similar to their mammalian analogues in terms of biochemical and pharmacological properties. In order to study the regional distribution of these receptors, we have applied the GSH assay to polyps amputated at different levels of the body column. The response to 1-10 µmol l −1 GSH of polyps lacking either peduncle and foot or the entire body columns (heads) was not different from control, whole animals. In the presence of GABA or muscimol, duration of the response was significantly decreased in heads; the decrease was suppressed by the GABA antagonists gabazine and bicuculline. By contrast, in animals lacking peduncle and foot, duration of the response did not vary upon GABA administration. Conversely, in the presence of glycine, duration of the response in heads preparations was similar to control, whereas in footless polyps, it was significantly reduced. The decrease was mimicked by the glycine agonists taurine and β-alanine, and counteracted by strychnine. These results suggest a regional distribution of receptors to GABA and glycine in the neuromuscular circuitry modulating the feeding behaviour.

Multiple neuronal networks coordinate Hydra mechanosensory behavior

“…Patch-clamp electrophysiology of individual neurons in Hydra has thus far been unsuccessful despite attempts by many research groups, and minimally invasive, cell-type specific neuromodulation techniques such as optogenetics have yet to be developed for Hydra . However, the animal’s regenerative abilities allow us to resect large portions of tissue without killing the animal, thus we can borrow from the tradition of lesioning brain regions to study their functions ( Rushforth et al, 1963 ; Vaidya et al, 2019 ; Krug et al, 2015 ; Passano and McCullough, 1964 ; Pierobon, 2015 ).…”

Multiple neuronal networks coordinate Hydra mechanosensory behavior

“…However, the animal's regenerative abilities allow us to resect large portions of tissue without killing the animal, and thus we can borrow from the tradition of lesioning brain regions to study their functions 52,[58][59][60][61] .…”

“…This recovery time helps to reduce the confounding contributions from initial tissue regeneration and allows animals to recover enough to tolerate microfluidic immobilization. This period is long enough to allow the wounds to close, the molecular response to injury to be completed 62,63 and the initial molecular events of regeneration to start, but it is not long enough for the animal to regenerate the lost neurons, which takes approximately 30 -72 hours 37,61,64,65 (Supp. Fig.…”

“…This recovery time helps to reduce the confounding contributions from initial tissue regeneration and allows animals to recover enough to tolerate microfluidic immobilization. This period is long enough to allow the wounds to close, the molecular response to injury to be completed 62,63 , and the initial molecular events of regeneration to start; but it is not long enough for the animal to regenerate lost neurons, which takes approximately 30-72 hours (Figure 3 -Figure Supplement 1) 37,61,64,65 . We confirmed that 6-12 hours after resection the animals indeed showed loss of specific neuronal cell types by measuring the expression levels of subtype-specific neuronal markers via qPCR (Figure 3 We began resection studies by removing the peduncle and basal disk to create a "footless" Hydra.…”

Loss of Neurogenesis in Aging Hydra

“…The feeding behavior in Hydra is characterized by the capture of preys on the tentacles, the subsequent opening of the mouth and the coordinated movement of the tentacles to favor the ingestion of the preys through the mouth. This complex behavior is triggered by reduced glutathione release from the captured prey (Loomis, ; Grosvenor et al , ; Pierobon, ). Here animals were individually exposed to preys, that is, swimming Artemias , for 15 s and the number of preys fixed on the tentacles was counted.…”