Abstracts

Rationale: There is an undisputable link between stress and epilepsy, however mechanisms of this link are still poorly understood. The hypothalamic paraventricular nucleus (PVN), a structure regulating the stress response may be a key brain site at the intersection of stress and seizures. In this study, we used our established model of cryptogenic Infantile Spasms (cIS) as a tool to investigate the role of PVN in control of spasms and studied in vivo effects of pharmacological manipulations in PVN, as well as effects of these manipulations on spasms in the cIS model. Additionally, we studied the effects of blockade of corticotropin-releasing factor (CRF) receptor type 1 (CRFR1) in a main target of PVN, the arcuate nucleus (ARC) on spasms.Methods: The cIS model consists of the prenatal priming with betamethasone on the gestational day 15 and postnatal trigger of spasms on the postnatal day (PD) 15. We used unilateral microinfusions of GABA(A) receptor agonist muscimol or antagonist bicuculline in the PVN for pharmacological manipulations. To test the effects of antagonism of CRF action on development of spasms, we also unilaterally microinfused CRFR1 antagonist CP376395 into the ARC.Results: Unilateral microinfusion of muscimol into the PVN induced by itself spasm-like behavior in PN15 rats. At about 4-5 min after infusion of muscimol animals started curling up in a ball-like position resembling spasms observed in response to the NMDA-trigger. This finding indicates that impairment of GABAergic transmission in the PVN may lead to a spasm-like phenotype. Although muscimol infusion itself had a dramatic effect, this pretreatment did not affect development of NMDA-triggered spasms. Unilateral infusion of bicuculline into the PVN induced agitation at about 5-7min after infusion, which vanished within 5-8 min. Unlike muscimol, bicuculline pretreatment significantly decreased the number and delayed the onset of NMDA-triggered spasms compared to vehicle-infused controls. Further, pretreatment with the intra-ARC infusion of CRFR1 antagonist significantly decreased number and delayed the onset of NMDA-triggered spasms compared to vehicle-infused controls in a dose-dependent manner.Conclusions: Our findings identify the PVN as a connecting structure between stress axis and cIS. These data demonstrate that GABAergic hyperfunction in the PVN of immature rats leads to a spasm-like behavior, while GABAergic hypofunction in the PVN leads to successful control of spasms. Additionally, a blockade of the PVN-ARC network by CRFR1 antagonist effectively controlled the spasms highlighting importance of the role of the PVN network in cIS. Supported by Citizens United for Research in Epilepsy (CURE) Infantile Spasms Research Initiative and the NIH grant, NS072966.