This work attempted to "biochemically" map the brain structures that are recruited at the different stages of pentylenetetrazole (PTZ) kindling (in a model of temporal lobe epilepsy induced by a repeated, systemic administration of PTZ, at a subconvulsive dose of 35 mg/kg). We observed substantial changes in the levels of noradrenaline (NA), 5-hydroxytryptamine (5-HT), dopamine (DA), and their metabolites in the brain structures known to be recruited in the course of kindling, i.e., the piriform, entorhinal and prefrontal cortices, and the hippocampus (in vitro). Kindling of seizures induced time-, seizure-, and structure-dependent increases in the local levels of NA, 5-HT, 5-hydroxyindolacetic acid, DA, homovanillic acid, and 3,4-dihydroxyphenylacetic acid. Surprisingly, limited changes in monoamines (NA and 5-HT) were found in the amygdala. The most potent and widespread effects concerned the serotonergic system, indicating a possible protective role of its enhanced activity in the control of the kindling of seizures. These new data indicate a pattern of changes in the basal activity of local monoaminergic innervation of brain limbic structures, accompanying the induction and propagation of seizures.