Amygdala-kindled seizures increase the expression of corticotropin-releasing factor (CRF) and CRF-binding protein in GABAergic interneurons of the dentate hilus

doi:10.1016/S0006-8993(96)01157-2

Brain Research

Volume 745, Issues 1–2, 16 January 1997, Pages 248-256

https://doi.org/10.1016/S0006-8993(96)01157-2 Get rights and content

Abstract

Kindling, a model of temporal lobe epilepsy, induces a number of neuropeptides including corticotropin-releasing factor (CRF). CRF itself can produce limbic seizures which resemble kindling in some aspects. However, tolerance to the convulsant effects of CRF develops rapidly. Hypothetically, this could be explained should seizures also induce the CRF-binding protein (CRF-BP), which has been postulated to restrict the actions of CRF. Therefore, in the present study, we used in situ hybridization to examine the effects of amygdala-kindled seizures on the mRNA levels of CRF and CRF-BP. Kindled seizures markedly elevated CRF and CRF-BP in the dentate gyrus of rats. CRF and CRF-BP were induced almost exclusively in GABAergic interneurons of the dentate hilus. The CRF and CRF-BP interneurons also expressed neuropeptide Y but not cholecystokinin. CRF appeared to have an excitatory role in the dentate gyrus as it decreased the afterhyperpolarization of dentate granule neurons. These results suggest that CRF may contribute to the development of amygdala kindling. However, the compensatory induction of CRF-BP may serve to limit the excitatory effects of CRF in the dentate gyrus.

Introduction

Corticotropin-releasing factor (CRF) is a neuropeptide important in the endocrine and behavioral regulation of the stress response. Additionally, CRF may act as an excitatory neurotransmitter or neuromodulator in the central nervous system (CNS). Central administration of CRF increases neuronal firing, particularly in the locus coeruleus [34]and the hippocampus where it inhibits the slow afterhyperpolarization (AHP) 1, 28. Moreover, ovine CRF, when injected intracerebroventricularly (i.c.v.) into rodents, produces tonic clonic seizures after a 3–7 hour delay [11]. Epileptiform activity begins in the amygdala and then spreads to the dorsal hippocampus and cerebral cortex [3].

The unusually long latency to produce seizures led us to investigate whether i.c.v. CRF was producing a kindling-like stimulation of the limbic system that eventually resulted in full-blown motor seizures as suggested by Ehlers. Indeed, we found that pretreatment with ovine CRF accelerated the development of subsequent electrical kindling of the amygdala [36]. However, the role of CRF in limbic kindling is complicated by several observations. First, in contrast to its facilitation of electrical kindling, daily administration of CRF quickly produced tolerance to its own convulsant effects [36]. Likewise, prior electrical kindling of the amygdala prevented seizures in response to subsequent CRF administration. And unlike ovine CRF, administration of rat CRF does not consistently produce generalized seizures, and the epileptiform activity is confined to the dorsal hippocampus 20, 21.

Some of the seemingly paradoxical effects of CRF administration might be explained by the rather complex physiology of CRF, whose actions are regulated not only by multiple receptors, but also by a non-receptor CRF-binding protein (CRF-BP) [25]. CRF-BP mRNA is widely distributed in the CNS including the amygdala and hippocampal formation [26]. The role of CRF-BP is not clear, but it may serve to limit the action of CRF. Interestingly, ovine CRF binds to the rat CRF receptor but not to the CRF-binding protein.

In a previous study, we found that amygdala-kindled seizures induced CRF in the hilus of the dentate gyrus [32]. The hilus, or polymorphic layer, of the dentate gyrus contains a heterogeneous population of interneurons, some of which express GABA and serve to inhibit granule neurons. These hilar interneurons can be further subdivided according to the various neuropeptides (neuropeptide Y, somatostatin, cholecystokinin etc.) that are co-expressed with GABA (see [24]for review). Which of the many hilar interneuron subtypes express CRF is unknown. Moreover, the functional role of CRF in the dentate gyrus has not been described. Therefore, the purpose of the present investigation was three-fold: first to determine what effect, if any, CRF might have on the electrophysiology of dentate granule neurons; second, to characterize neurochemically the hilar interneurons in which CRF is expressed; and third, to investigate the effects of kindling on the expression of CRF binding protein with the hope of shedding light on the apparent cross-tolerance between kindled and CRF-induced seizures and the differing convulsant properties of ovine and rat CRF.

Section snippets

Amygdala kindling

Male Sprague-Dawley rats (Taconic Farms, Germantown, NY) weighing approximately 300 g were sterotaxically implanted with a bipolar platinum-iridium electrode into the left amygdala (5.7 mm posterior, 4.5 mm lateral and 2 mm ventral to intra-aural zero). One week following surgery, rats received once daily stimulation with 800 μA of current at 60 Hz for 1 s, or were handled in an identical manner but did not receive current (sham controls). Rats were stimulated until they had multiple

Effects of kindled seizures on CRF and CRF-BP

Using in situ hybridization, we examined the effects of amygdala-kindled seizures on the expression of CRF and CRF-binding protein in the rat brain. As previously reported [32], kindled seizures dramatically increased CRF mRNA expression in the dentate hilus (Fig. 1). And again, kindled seizures did not alter CRF mRNA levels in the hippocampal pyramidal layers, cerebral cortex, or central nucleus of the amygdala. In the present study, we also examined the effects of kindling on the expression

CRF and CRF-BP co-expression in GABAergic interneurons of the dentate hilus

From our initial study on CRF expression during kindling, we had tentatively proposed that CRF was being induced in dentate hilar interneurons which probably were GABAergic [32]. In the present study, we found that indeed, not only CRF but also CRF-BP, were induced almost exclusively in GABAergic interneurons of the dentate gyrus by kindling. GABAergic neurons, in addition to those in the dentate gyrus, may also express CRF. We observed in sham animals that many GAD neurons in the cerebral

References (41)

Aldenhoff, J.B., Gruol, D.L., Rivier, J., Vale, W. and Siggins, G.R., Corticotropin releasing factor decreases...
Bakst, I., Avendano, C., Morrison, J.H. and Amaral, D.G., An experimental analysis of the origins of somatostatin-like...
Baram, T.Z., Hirsch, E., Snead III, O.C. and Schultz, L., Corticotropin-releasing hormone-induced seizures in infant...
Baram, T.Z. and Schultz, L., Corticotropin-releasing hormone is a rapid and potent convulsant in the infant rat, Dev....
Bishop, G.A., Neuromodulatory effects of corticotropin releasing factor on cerebellar purkinje cells: an in vivo study...
Burgard, E.C. and Sarvey, J.M., Long-lasting potentiation and epileptiform activity produced by GABAB receptor...
Ceccatelli, S., Eriksson, M. and Hokfelt, T., Distribution and coexistence of corticotropin-releasing factor-,...
Chen, R., Lewis, K.A., Perrin, M.H. and Vale, W.W., Expression cloning of a human corticotropin-releasing-factor...
Clark, M., Post, R.M., Weiss, S.R.B., Cain, C.J. and Nakajima, T., Regional expression of c-fos mRNA in rat brain...
Deller, T. and Leranth, C., Synaptic connections of neuropeptide Y (NPY) immunoreactive neurons in the hilar area of...

Ehlers, C.L., Henriksen, S.J., Wang, M., Rivier, J., Vale, W. and Bloom, F.E., Corticotropin releasing factor produces...

Higuchi, H., Yang, H.-Y.T. and Sabol, S.L., Rat neuropeptide Y precursor gene expression, J. Biol. Chem., 263 (1988)...

Imaki, T., Nahan, J.-L., Rivier, C., Sawchenko, P.E. and Vale, W., Differential regulation of corticotropin-releasing...

Kohler, C., Eriksson, L.G., Davies, S. and Chan-Palay, V., Co-localization of neuropeptide tyrosine and somatostatin...

Kosaka, T., Wu, J.-Y. and Benoit, R., GABAergic neurons containing somatostain-like immunoreactivity in the rat...

Lee, E.H., Chang, S.Y. and Chen, A.Y., CRF facilitates NE release from the hippocampus: a microdialysis study,...

Leranth, C., Malcolm, A.J. and Frotscher, M., Afferent and efferent synaptic connections of somatostatin-immunoreactive...

Lovenberg, T.W., Liaw, C.W., Grigoriadis, D.E., Clevenger, W., Chalmers, D.T., De Souza, E.B. and Oltersdorf, T.,...

Lyons, M.K., Anderson, R.E. and Meyer, F.B., Corticotropin releasing factor antagonist reduces ischemic hippocampal...

Marrosu, F., Fratta, W., Carcangiu, P., Giagheddu, M. and Gessa, G.L., Localized epileptiform activity induced by...

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Research reportAmygdala-kindled seizures increase the expression of corticotropin-releasing factor (CRF) and CRF-binding protein in GABAergic interneurons of the dentate hilus