Abstracts

There currently is no available animal model that reproduces the spectrum of neurological and endocrinological abnormalities in women with epilepsy. We tested the hypothesis that treatment with the convulsant pilocarpine could produce a range of mild and severe seizures in female rats that would parallel many of the neurological and endocrinological problems reported by women with epilepsy.
Adult (60-120 days old) female Sprague-Dawley rats were injected on the morning of proestrus, estrus, metestrus, or after ovariectomy, with atropine methylbromide (1 mg/kg, s.c.), and 30 min later with pilocarpine (350 mg/kg, i.p.). Diazepam was administered 1 hr after the onset of status. Controls received all drugs, but an equivalent volume of saline was substituted for pilocarpine. Cycle stage was assessed daily by vaginal cytology. Two months after pilocarpine injection, animals were weighed, and then anesthetized. Blood was removed for subsequent radioimmunoassay to determine estradiol, progesterone, and testosterone levels. Animals were perfused, and ovaries were removed. Immunocytochemistry used free-floating 50 [mu]m vibratome sections to examine the perfused brain with antibodies to NeuN (a neuronal marker), neuropeptide Y, the calcium binding protein calbindin, and glial fibrillary acidic protein (GFAP). Nissl or hematoxylin and eosin stain was used to examine 30-50 [mu]m-thick sections of ovaries.
Proestrus (n=3/4) and ovariectomized rats (n=7/8) were more likely to enter status epilepticus than animals at estrus (n=1/6) or metestrus (n=2/7; [chi]² test, p [lt] 0.05). Animals that had status developed recurrent seizures and demonstrated structural changes in hippocampus similar to male rats with chronic seizures after pilocarpine-induced status, such as neuronal loss, mossy fiber sprouting, and ectopic hilar granule cells. Hypothalamic regions were also affected, although gliosis and cell loss were not striking. Females often became acyclic after pilocarpine injection, even if the initial response to pilocarpine was only 1-2 stage 5 seizures. Acylicity usually developed in conjunction with abnormal weight gain and ovarian cysts. Animals that became acyclic had high testosterone levels at the time of death relative to pilocarpine-treated animals that continued to cycle and were euthanized on metestrus (106 [plusmn] 16.3 pg/ml, n=9 vs. 51.0 [plusmn] 6.1, n=10; Student[apos]s t-test, p[lt] 0.05), but both were much lower than males ([gt]1000, n=3) .
The results suggest that pilocarpine-treatment of female rats can be used to examine neurological and reproductive disorders reported in women with epilepsy. They also show that even a history of seizures, without chronic epilepsy, may lead to reproductive changes. Many changes in female rats were similar to Polycystic Ovarian Syndrome in women with epilepsy. We conclude that laboratory rats can be used to examine issues relevant to women with epilepsy.
[Supported by: NIH grant 37562 and 38285.]