CCK-8 prevents the development of kindling and regulates the GABA and NPY expression in the hippocampus of pentylenetetrazole (PTZ)-treated adult rats

Neuronal loss and irreversible brain damage often cause the worsening of symptoms and the decreased efficacy of pharmacological treatment occurring in epileptic patients and animal models of kindling. Recently we reported that the neurotransmitter/neuromodulatory peptide Cholecystokinin-8 (CCK-8) is able to induce the structural and functional neuronal recovery of chemical- and surgical-induced lesions when i.p. injected in rodents. The present study therefore, was aimed at verifying the hypothesis that treatment with a CCK-8 dose having a neuroprotective action might affect brain alterations and the development of kindling in adult rats receiving the convulsant agent pentylenetetrazole (PTZ). Compared to rats receiving Saline prior to PTZ, which manifested clonic-tonic seizures (Class 5 behavioural change scale) after three weeks of treatment, rats pre-treated with CCK-8 showed an improvement of behavioural score exhibiting myoclonus and occasionally tonic seizures (Class 3/4). This decreased susceptibility to develop convulsions was associated with the recovery of PTZ-induced reduction of ChAT levels in forebrain and GABA/GAD expression in the hippocampus. Furthermore, NPY immunoreactivity distribution and NPY mRNA levels were also increased in the hippocampus of rats receiving CCK-8 injection before each PTZ treatment. These data indicate that CCK-8 possesses the ability to prevent and/or suppress the convulsant effects of PTZ by stimulating the synthesis of neurotransmitters/peptides involved in the inhibition of hippocampal hyper-excitability. Our findings suggest that CCK-8 may have anticonvulsant and neuroprotective properties that merit further investigation.