Neurotoxin that induces excitatory symptoms in mice following intracranial administration. No symptoms are observed after intraperitoneal and intravenous (tail vein) injections. Expressed by the venom duct. The cysteine framework is XXIII (C-C-C-CC-C). Does not affect (up to 50 uM) the Nav1.7/SCN9A channel, Drosophila Shaker channel and rat KCa1.1/KCNMA1 channel expressed in HEK293 cell, as well as on whole cell current of neurons from neonatal rat hippocampus and prefrontal cortex. In addition, no detectable effect is observed on either action potential amplitude and duration or Na(+) and Ca(2+) current amplitude and kinetics when im23a is tested on action potentials and depolarization-activated Na(+) and Ca(2+) currents in rat DRG neurons (PubMed:22399292). Belongs to the conotoxin K superfamily.