Amygdala kindling decreases insulin-like growth factor-I receptor binding sites in the rat hippocampus

The neural excitability characteristic of kindling has been linked to structural alterations such as mossy fiber sprouting and synaptic reorganization within the hippocampus. Recent evidence suggests that growth factors may play a key role in kindling-related synaptic plasticity. Insulin-like growth factors-I and -II (IGF-I/-II) and insulin are structurally-related pleiotropic growth factors known to be involved in neural growth and differentiation. In the present study, we investigated the effect of kindling on [125I]IGF-I, [125I]IGF-II and [125I]insulin receptor binding in the hippocampus of adult rats. Our results indicate a progressive decrease in [125I]IGF-I (but not [125I]IGF-II or [125I]insulin) binding sites in the CA1, hilus and the granule cell layer of the kindled rats compared to sham-stimulated rats. These results, in keeping with the established neurotrophic effects of IGF-I, suggest a potential role for this growth factor in mediating the structural alterations associated with kindling.