an aBungarotoxin neuronal nicotinic receptor antagonist with selective nanomolar affinity for a subtype of neuronal nAChR in the brain that probably incorporates the Alpha7 subunit, compared with micromolar affinity at muscle nAChR and at aBungarotoxin insensitive neuronal nAChR.

C₁₉-norditerpenoid alkaloid C₃₇H₅₀N₂O₁₀.HClO₄ derivative of Methyllycaconitine from plants of the Delphinium genus, Ranunculaceae.

• Molecular Weight : 782 Da.
  
  
• Melting Point : 185-187 °C.
  
  
• Solubility in : slightly in methanol; not well in water, ethanol.
  
  
• Purity min. : 95 % (TLC, NMR).
  
  
• Biological Activity : medium-lasting myorelaxing activity; as a tertiary amine, Methyllycaconitine (MLA) crosses histohematic barriers and is active orally: blockage of Nicotinic cholinoreceptors of striated muscles at 2.5-3.5 mg/kg intravenously and 30-40 mg/kg orally; MLA relates to the non-depolarizing competitive myorelaxing agents, and its antagonists are Galanthamine and Neostigmine. 0.5-2 mg/kg intravenously, has an hypotensive activity due to the inhibition of nervous influx transmission in sympathetic and parasympathetic ganglia. MLA acts directly on the brain and spinal cord; enhances the amplitude of monosynaptic potentials in inhibiting the Nicotinic receptors of Renshaw cells; removes totally the inhibiting effect of Nicotine on spinal cord monosynaptic responses; intravenously in cats, MLA has been shown to interact with brain Nicotinic receptors, eliminating variations of EEG caused by subecholine; recent studies (see attached sheet) show that MLA and some related diterpenoid alkaloids act as neuronal Alpha-Bungarotoxin sensitive brain nicotinic receptors antagonist.
  
  
• Toxicity (LD₅₀) : mice (i.v.): 3.9 mg/kg. mice (i.p.): 19.5 mg/kg. mice (orally): 40.0 mg/kg.
  
  
• Storage recommendations : Storage and reconstitution recommendations: Store at +4°C, in dark place. Dissolves in water :
  - at room temperature : up to 0,15%
  - at 40°C : up to 0,3%
  
  
• CAS Reg. No. : 40819-78-1
  
  
• Bibliography :
  
  1. Pereira et al., "Identification and functional characterization of a new agonist site on nicotinic acetylcholine receptors of cultured hippocampal neurons." Journ. Pharm. Exp. Ther. 1993 265(3):1474-1491
  2. Alkondon et al., "Blockade of nicotinic currents in hippocampal neurons defines methyllycaconitine as a potent and specific receptor antagonist." Mol. Pharmacol. 1992 41(4):802-808
  3. Machkovski et al., "New neuromuscular blocking agents: basic and applied aspects." Berlin 1986 391-397