Quantitative autoradiography of [¹²⁵I] apamin binding sites in the central nervous system

The binding sites for [¹²⁵I] apamin in the central nervous system of rat, guinea-pig, chicken and frog were assessed by quantitative autoradiography on X-ray film. In rat and guinea-pig brain apamin labels preferentially the limbic-olfactory system, i.e. nucleus olfactorius, nuclei septi, habenula and hippocampus. In the rat spinal cord the peptide binds preferentially to the substantia gelatinosa. Tectum opticum and nuclei isthmi are labelled in chicken brain. In frog brain no preferentially 'apamin-stained' area was found. The role of the cerebral binding sites is still unknown, whereas the spinal sites may be involved in apamin poisoning.