Estradiol does not affect spasms in the betamethasone‐NMDA rat model of infantile spasms

Abstract

SUMMARYObjective: This study attempted to validate the effects of neonatal estradiol in ameliorating the spasms in the prenatally betamethasone-primed N-methyl-D-aspartate (NMDA) model of infantile spasms in rats as shown previously in a mouse Arx gene knock-in expansion model of infantile spasms. Methods: Neonatal rats prenatally exposed to betamethasone (on day 15 of pregnancy) were treated with subcutaneous 40 ng/g estradiol benzoate (EB) between postnatal days (P)3-P10 or P0-P5. A synthetic estrogen analogue, diethylstilbestrol, was used between P0 and P5 (2 lg per rat, s.c.). On P12, P13, and P15, the rats were subjected to NMDA-triggered spasms, and latency to onset and number of spasms were evaluated. Rats with EB on P3-P10 were tested after spasms in the open field, novel object recognition, and elevated plus maze to determine effects of treatment on behavior. Additional rats with P3-P10 or P0-P5 EB were investigated for c-aminobutyric acid (GABA)ergic neurons (glutamate decarboxylase [GAD]67 expression) in the neocortex. As a positive control, a group of rats received either subcutaneous adrenocorticotropic hormone (ACTH) (2 3 0.3 mg/kg on P12 and 3 3 0.3 mg/kg on P13 and P14) or vehicle after the first episode of spasms on P12. Results: Neither EB treatment nor diethylstilbestrol consistently affected expression of spasms in this model, although we found a significant increase in GAD67-immunopositive cells in the neocortex after P3-P10 and P0-P5 EB treatment, consistent with a study in mice. Behavioral tests showed increase in lateralization in male rats treated with P3-P10 EB, a behavioral trait usually associated with female sex. Diethylstilbestrol treatment in male rats resulted in arrested pubertal descent of testes. ACTH had robust effects in suppressing spasms. Significance: Treatment of infantile spasms (IS) using neonatal EB may be justified in those cases of IS that present with detectable deficits in GABAergic neurons. In other types of IS, the efficacy of neonatal EB and its analogues is not supported.

ACTH and PMX53 recover synaptic transcriptome alterations in a rat model of infantile spasms

“…Our previous studies indicated that ACTH suppresses the occurrence of NMDA-triggered spasms in both sexes 20 , 24 . Here we show that the complement C5ar1 receptor antagonist, PMX53, also reduced spasms, suggesting contribution of the innate inflammatory system, represented by C5a, to IS.…”

“…1B ). Pups were treated with either ACTH (twice on P12 and three times a day on P13 and P14, each dose of 0.3 mg/kg sc; the effective treatment paradigm in our IS model) 20 , 24 , PMX53 (one daily dose of 0.6 mg/kg sc on P12, P13, P14 and P15; effective previously against seizure in epilepsy models) 10 or saline as control, on P12, P13, P14 and P15. Spasms were followed for 60 min after the trigger and latency to onset of spasms from the trigger and number of spasms was calculated during the observation period.…”

“…We have developed a two-hit animal model of infantile spasms in rats, consisting of prenatal priming with corticosteroids and postnatal trigger of spasms with NMDA 18 , 19 . Prenatal priming with synthetic corticosteroids (or stress) increases susceptibility to postnatal NMDA trigger of flexion spasms and renders spasms responsive to ACTH treatment 20 . Spasms can be triggered by NMDA only during the period of brain development 21 , 22 relevant for human IS 23 .…”

Infantile Spasms: An Update on Pre-Clinical Models and EEG Mechanisms

“…Using this model, the efficacy of several compounds has been tested. In contrast to the Arx expansion model, neonatal 17β-estradiol failed to provide protection from NMDA-induced spasms [72]. The successful treatment of NMDA-induced spasms with ACTH and vigabatrin [73] suggests that both steroid hormones and GABAergic inhibition play a critical role in IS generation.…”

Preclinical Screening for Treatments for Infantile Spasms in the Multiple Hit Rat Model of Infantile Spasms: An Update

“…A recent report in the prenatal betamethasone/postnatal NMDA acute model of spasms also did not report any effects of 17β-estradiol early treatment (PN3-10) on NMDA spasms induced on PN12, PN13, and PN15 male and female rats [54]. We did not observe any differences in the developmental milestones or weights between 17β-estradiol or oil-treated male rats till PN13, although it was previously reported that weight gain is increased in estradiol-treated mixed male and female PN15 rats in the prenatal betamethasone/postnatal NMDA model [54]. In addition, the differences in species (mouse vs rats) and neurodevelopmental effects of the altered genetic background in ARX (GCG)10+7 mouse model may contribute to the differences in efficacy.…”