Apamin induces plastic changes in hippocampal neurons in senile Sprague-Dawley rats

Apamin is a neurotoxin extracted from honey bee venom and is a selective blocker of small‐conductance Ca²⁺‐activated K⁺ channels (SK). Several behavioral and electrophysiological studies indicate that SK‐blockade by apamin may enhance neuron excitability, synaptic plasticity, and long‐term potentiation in the CA1 hippocampal region, and, for that reason, apamin has been proposed as a therapeutic agent in Alzheimer's disease treatment. However, the dendritic morphological mechanisms implied in such enhancement are unknown. In the present work, Golgi–Cox stain protocol and Sholl analysis were used to study the effect of apamin on the dendritic morphology of pyramidal neurons from hippocampus and the prefrontal cortex as well as on the medium spiny neurons from the nucleus accumbens and granule cells from the dentate gyrus (DG) of the hippocampus. We found that only granule cells from the DG and pyramidal neurons from dorsal and ventral hippocampus were altered in senile rats injected with apamin. Our research suggests that apamin may increase the dendritic morphology in the hippocampus, which could be related to the neuronal excitability and synaptic plasticity enhancement induced by apamin. Synapse 2011. © 2011 Wiley‐Liss, Inc.