Con-G[γ7K] and Con-G[S16Y] also show positive results in morphine withdrawal. Con-T-based Con-T[K7γ] is a synthetic Con-T peptide, where the serine at position 7 is replaced with Gla residue. Like Con-G, it has higher affinity for Mg2+ than for Ca2+, but does not dimerize in the presence of Mg2+. Chemistry Biochemically, conantokins have a distinctive high γ-carboxyglutamate content and low cysteine content. Conantokins typically lack disulfide bonds, in contrast to most families of conotoxins, which have an unusually high density of disulfide cross-links. The inhibition of NMDAR-mediated spontaneous EPSCs (sEPSCs) and NMDA-gated currents in cortical neurons might be a result of actions on both diheteromeric (NR1/NR2B) and triheteromeric (NR1/NR2A/NR2B) NMDAR. Mode of action Con-G does not act directly at the glycine binding site. It can attenuate both the amplitude and the decay time constant of NMDA-mediated EPSCs and significantly and reversibly affect other different properties of NMDAR-mediated sEPSCs in cultured neurons. The effect of Con-G on the frequency of the sEPSCs most likely relates to antagonizing the NMDAR. Target Conantokins target NMDAR. Each subtype selectively targets different subunits of the receptor. Toxicity Some of these peptide effects are age-dependent, such as the induction of sleep-like state in young mice and hyperactive behavior in older mice. Intrathecal administration of doses greater than 300 pmol produced motor impairment in mice. Con-G, Con-R and Con-L cause behavioral toxicity at similar doses. Thus the difference in the C-terminal sequence might affect the anticonvulsant and behavioral toxicity profile. References External links "conotoxin+B+superfamily" Uniprot family: "conotoxin b superfamily" - List of curated Conantokins in UniProt Ion channel toxins Neurotoxins Snail toxins NMDA receptor antagonists