Snail receptor

Several hundred species of Conus snails produce a wide array of small (12-30 AA) and mostly tightly disulfide bonded peptide ligands with high affinity for a diverse set of receptor and ion channel types. 

Muschamp, J.W. and Fong, P.P. (2001) Effects of the serotonin receptor ligand methiothepin on reproductive behavior of the freshwater snail Biomphalaria glabrata reduction of egg laying and induction of penile erection. Journal of Experimental Zoology 289, 202-207. 

Cone snails, Conus spp., have been investigated because of their production of conotoxin peptides. From an evolutionary standpoint, the production of conotoxins is quite interesting due to their wide range of neurophysiological activities. The conotoxins are small peptides, 10-30 amino acids, with conformations constrained by multiple disulfide bonds that target a number of receptors in vertebrate and invertebrate nervous systems. Cone snails use these toxins to immobilize prey, which allows the relatively slow-moving cone snails to feed on fish and worms. The wide variety of conotoxins isolated and the hypervariability within peptide sequences has led some to hypothesize a combinatorial biosynthetic approach for the production of conotoxins.116117... 

D-Ala-deltorphin-II induces 6-opiate receptor mediated analgesia in frogs [55] and also in the invertebrate land snail (Cepaea nemoralis) [56]. When administered by intrathecal injection in rats, D-Ala-deltorphin-II produces a dose-related inhibition of the tail-flick response (threshold 0.6 nmol/rat). Its inhibitory effect lasts 10 60 min, depending on the dose, and is naltrindole reversible [57]. Wang et al. [25] demonstrated that D-Ala-deltorphin-II inhibited A6 and C fiber evoked responses from nociceptive neurons in the superficial and deeper dorsal horn of the rat medulla. 

One of the most extensively studied families of peptide toxins, the conotoxins, is isolated from marine cone snails.140 141 Each snail produces a suite of 100-200 peptides in its venom, which is used for the capture of prey, and given that more than 500 species of cone snails are thought to exist, conotoxins represent an enormous diversity of peptide toxins. They have been classified into families, based on their target receptor specificity, and superfamilies, according to their... 

The effect of AN was stndied on the neurones of two snail species, and it was concluded that AN affects the neuronal membrane of neurones acting on ACh receptors (Kiss et al. 2002). 

Synaptic transmission between pairs of neurons in Aplysia (a marine snail) is enhanced by serotonin, a neurotransmitter that is released by adjacent intemeurons. Serotonin binds to a 7TM receptor to trigger an adenylate cyclase cascade. The rise in cAMP level activates PKA, which facilitates the closing of potassium channels by phosphorylating them. Closure of potassium channels increases the excitability of the target cell. 

Relatively little is known about the effects of dioxins in invertebrates. Controlled laboratory studies with dioxin-contaminated sediments reported no effects on amphipod mortality. Some studies have shown reduced reproductive success in worms and snails. Some invertebrates have been shown to express Ah receptors, but these receptors do not appear to bind dioxins, thus invertebrates are less sensitive to dioxin toxicity. 

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