Apamin is an 18 amino acid globular peptide neurotoxin found in apitoxin (bee venom).

[4] The first symptoms of apitoxin (bee venom), that are now thought to be caused by apamin, were described back in 1936 by Hahn and Leditschke.

Bee venom contains many other compounds, like histamine, phospholipase A2, hyaluronidase, MCD peptide, and the main active component melittin.

The three-dimensional structure of apamin has been studied with several spectroscopical techniques: HNMR, Circular Dichroism, Raman spectroscopy, FT-IR.

Glutamine7 was altered by formation of an amide bond with glycine ethyl ester, this resulted in a decrease in toxicity of a factor 2.0.

These channels are responsible for the afterhyperpolarizations that follow action potentials, and therefore regulate the repetitive firing frequency.

[8] Transport of potassium ions out of the cell along their concentration gradient causes the membrane potential to become more negative.

[9] It is likely that the inhibition of SK channels is caused by blocking of the pore region, which hinders the transport of potassium ions.

The kinetics of labeled derivatives of apamin were studied in vitro and in vivo in mice by Cheng-Raude et al.

The peptide apamin is small enough to pass the glomerular barrier, facilitating renal excretion.

The central nervous system, contrarily, was found to contain only very small amounts of apamin.

[10] However, these results disagree with a study of Vincent et al. After injection of a supralethal dose of radioactive acetylated apamin in mice, enrichment was found in the spinal cord, which is part of the target organ.

Some other organs, including kidney and brain, contained only small amounts of the apamin derivative.

[13] In rats, apamin was found to cause tremor and ataxia, as well as dramatic haemorrhagic effects in the lungs.

The peripheral nervous system contains the nerves and ganglia outside of the brain and spinal cord.

Dopamine, which is depleted in this disease, will be released from midbrain dopaminergic neurons when these SK channels are inhibited.