Effects of neurotransmitter receptor antagonists on sea urchin righting behavior and tube foot motility

Abstract

Sea urchins, as echinoderms, occupy an interesting position in animal phylogeny in that they are genetically closer to vertebrates than the vast majority of all other invertebrates but have a nervous system that lacks a brain or brain-like structure. Despite this, very little is known about neurobiology of the adult sea urchin, and how the nervous system, is utilized to produced behavior. Here we investigate effects on the righting response of antagonists of ionotropic receptors for the neurotransmitters acetylcholine, GABA, and glycine, and antagonists of metabotropic receptors for the amines dopamine and norepinephrine. Antagonists slowed the righting response in a dose-dependent manner, with a rank order of potency of strychnine>haloperidol>propranolol>bicuculline>hexamethonium, with RT50s (concentrations that slowed righting time by 50%) ranging from 4.3 µM for strychnine to 7.8 mM for hexamethonium. It is also shown that both glycine and adrenergic receptors are needed for actual tube foot movement, and this may explain the slowed righting seen when these receptors are inhibited. Conversely, inhibition of dopamine receptors slowed the righting response but had no effect on tube foot motility, indicating that these receptors play roles more in the neural processing involved in the righting behavior, rather than the actual physical righting. Our results identity the first effects of inhibiting the glycinergic, dopaminergic, and adrenergic neurotransmitter systems in adult sea urchins and distinguish between the ability of sea urchins to right themselves, and the ability of sea urchins to move their tube feet.

Study on the Potential Mechanism of Semen Strychni against Myasthenia Gravis Based on Network Pharmacology and Molecular Docking with Experimental Verification

“…Strychnine, the most abundant alkaloid of SS, is highly toxic to humans and most domestic animals. Strychnine is a well-known potent antagonist of glycine receptors in the central nervous system of vertebrates and a potent blocker of various types of muscle and neuronal nicotinic acetylcholine receptors [ 23 ]. Strychnine has negligible antitumor, analgesic, and anti-inflammatory properties [ 24 ].…”

Thyroid hormone membrane receptor binding and transcriptional regulation in the sea urchin Strongylocentrotus purpuratus

“…We found that T4 (and to a lesser degree T3) upregulated beta-1 adrenergic receptor and the noradrenaline transporter SLC6A2 orthologs in our transcriptome analysis. While little work has been done on sea urchin adrenergic receptors, adrenergic signaling has been shown to be necessary for tube foot motility in adult sea urchins (124).…”

The dopamine receptor antagonist haloperidol disrupts behavioral responses of sea urchins and sea stars

“…To administer the drugs, animals were immersed in tanks containing ASW, 0.1% methanol or 0.1% methanol plus haloperidol where appropriate, for 1 h and the behavioral tests were conducted in the stated solutions. A 1 h preincubation has previously been found to be sufficient to allow drug absorption and observe behavioral effects of the drug on sea urchins (McDonald et al, 2022).…”

“…Righting assays were performed as in McDonald et al (2022). Briefly, animals were preincubated in test solutions for 1 h, and then were inverted and placed on their aboral side on the base of a tank containing ASW with or without the specified drugs.…”

“…Dopamine itself has been shown to modulate the stiffness of spine ligaments in the sea urchin Eucidaris tribuloides (Morales et al, 1993), and in sea stars dopamine has been detected in the regenerating arms of Asterina gibbosa (Huet and Franquinet, 1981), and can inhibit the luminescence of photocytes in the brittle star Amphipholis squamata (De Bremaeker et al, 2000). Additionally, it has recently been shown that the dopamine receptor antagonist haloperidol inhibits the righting response in the sea urchin S. purpuratus with an RT50 (drug concentration at which righting time was slowed by 50% of the maximum righting time) of 10.7 µmol l −1 (McDonald et al, 2022). In that study, haloperidol was found to not affect the motility of the tube feet, suggesting a role for dopamine receptors in the neural processing of the behavior rather than actual movement, which is achieved via the water vascular and tube feet systems.…”