Epilepsy and hormonal regulation: the patterns of GnRH and galanin immunoreactivity in the hypothalamus of epileptic female rats

Endocrine and reproductive alterations are frequently reported to occur in women with temporal lobe epilepsy as well as in female rats in different experimental models of limbic seizures. We have recently observed that rats with structural damage of limbic structures induced by sustained convulsions triggered by systemic administration of pilocarpine develop spontaneous seizures after a mean latency of 15 days. In order to investigate the possible substrate of endocrine alterations in epilepsy, changes of the gonadotropin-releasing hormone (GnRH) and the neuropeptide galanin (GAL) were studied in the hypothalamus of epileptic female rats after pilocarpine treatment. Female rats injected with pilocarpine (320-350 mg/kg, i.p.) and control cases injected with saline were killed 10-20 h, 10-15 or 60-90 days following treatment. In some of these animals colchicine was injected in the lateral cerebral ventricle 24 h before death. GnRH immunopositivity was observed in the hypothalamus in neuronal cell bodies, fi bers and punctate elements of both epileptic and control cases. A striking reduction of the density of GnRH-immunoreactive fibers and puncta was observed in the hypothalamus of the epileptic female rats killed 10-15 or 60-90 days following pilocarpine administration. No significant differences were observed in the number and size of GAL-immunoreactive perikarya of epileptic and control cases. The present findings suggest that a substantial rearrangement of GnRH-containing efferents, and in particular a loss of their terminal branches, occurs in the epileptic rat brain. Comparable regressive changes could account for alterations in endocrine and reproductive functions observed in temporal lobe epilepsy.