Skip to main content
PMC home page
Neuroscience Bulletin logoLink to Neuroscience Bulletin
. 2012 Nov 12;28(6):729–736. doi: 10.1007/s12264-012-1279-6

Expression of connexin 30 and connexin 32 in hippocampus of rat during epileptogenesis in a kindling model of epilepsy

Bijan Akbarpour 1,2, Mohammad Sayyah 1,✉, Vahab Babapour 3, Reza Mahdian 4, Siamak Beheshti 5, Ahmad Reza Kamyab 4
PMCID: PMC5561816  PMID: 23149765

Abstract

Objective

Understanding the molecular and cellular mechanisms underlying epileptogenesis yields new insights into potential therapies that may ultimately prevent epilepsy. Gap junctions (GJs) create direct intercellular conduits between adjacent cells and are formed by hexameric protein subunits called connexins (Cxs). Changes in the expression of Cxs affect GJ communication and thereby could modulate the dissemination of electrical discharges. The hippocampus is one of the main regions involved in epileptogenesis and has a wide network of GJs between different cell types where Cx30 is expressed in astrocytes and Cx32 exists in neurons and oligodendrocytes. In the present study, we evaluated the changes of Cx30 and Cx32 expression in rat hippocampus during kindling epileptogenesis.

Methods

Rats were stereotaxically implanted with stimulating and recording electrodes in the basolateral amygdala, which was electrically stimulated once daily at afterdischarge threshold. Expression of Cx30 and Cx32, at both the mRNA and protein levels, was measured in the hippocampus at the beginning, in the middle (after acquisition of focal seizures), and at the end (after establishment of generalized seizures) of the kindling process, by real-time PCR and Western blot.

Results

Cx30 mRNA expression was upregulated at the beginning of kindling and after acquisition of focal seizures. Then it was downregulated when the animals acquired generalized seizures. Overexpression of Cx30 mRNA at the start of kindling was consistent with the respective initial protein increase. Thereafter, no change was found in protein abundance during kindling. Regarding Cx32, mRNA expression decreased after acquisition of generalized seizures and no other significant change was detected in mRNA and protein abundance during kindling.

Conclusion

We speculate that Cx32 GJ communication in the hippocampus does not contribute to kindling epileptogenesis. The Cx30 astrocytic network localized to perivascular regions in the hippocampus is, however, overexpressed at the initiation of kindling to clear excitotoxic molecules from the milieu.

Keywords: connexin 30, connexin 32, hippocampus, kindling

References

  • [1].Vezzani M., French J., Bartfai T., Baram T.Z. The role of inflammation in epilepsy. Nat Rev Neurol. 2011;7:31–40. doi: 10.1038/nrneurol.2010.178. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • [2].Perez-Velazquez J.L., Carlen P.L. Gap junctions, synchrony and seizure. Trends Neurosci. 2000;23:68–74. doi: 10.1016/S0166-2236(99)01497-6. [DOI] [PubMed] [Google Scholar]
  • [3].Jin M.M., Chen Z. Role of gap junctions in epilepsy. Neurosci Bull. 2011;27:389–406. doi: 10.1007/s12264-011-1944-1. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • [4].Li J., Shen H., Naus C.C., Zhang L., Carlen P.L. Upregulation of gap junction connexin 32 with epileptiform activity in the isolated mouse hippocampus. Neuroscience. 2001;105:589–598. doi: 10.1016/S0306-4522(01)00204-4. [DOI] [PubMed] [Google Scholar]
  • [5].Rouach N., Avignone E., Meme W., Koulakoff A., Venance L., Blomstrand F., et al. Gap junctions and connexin expression in the normal and pathological central nervous system. Biol Cell. 2002;94:451–475. doi: 10.1016/S0248-4900(02)00016-3. [DOI] [PubMed] [Google Scholar]
  • [6].Beheshti S., Sayyah M., Golkar M., Sepehri H., Babaie J., Vaziri B. Changes in hippocampal connexin 36 mRNA and protein levels during epileptogenesis in the kindling model of epilepsy. Prog Neuropsychopharmacol Biol Psychiatry. 2010;34:510–515. doi: 10.1016/j.pnpbp.2010.02.006. [DOI] [PubMed] [Google Scholar]
  • [7].Elisevich K., Rempel S.A., Smith B., Allar N. Connexin 43 mRNA expression in two experimental models of epilepsy. Mol Chem Neuropathol. 1997;32:75–88. doi: 10.1007/BF02815168. [DOI] [PubMed] [Google Scholar]
  • [8].Söhl G., Maxeiner S., Willecke K. Expression and functions of neuronal gap junctions. Nat Rev Neurosci. 2005;6:191–200. doi: 10.1038/nrn1627. [DOI] [PubMed] [Google Scholar]
  • [9].McCracken C.B., Roberts D.C.S. A single evoked afterdischarge produces rapid time-dependent changes in connexin 36 protein expression in adult rat dorsal hippocampus. Neurosci Lett. 2006;405:84–88. doi: 10.1016/j.neulet.2006.06.025. [DOI] [PubMed] [Google Scholar]
  • [10].Pannasch U., Vargová L., Reingrube J., Ezan P., Holcman D., Giaume C., et al. Astroglial networks scale synaptic activity and plasticity. Proc Natl Acad Sci U S A. 2011;108:8467–8472. doi: 10.1073/pnas.1016650108. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • [11].Garbelli R., Frassoni C., Condorelli D.F., Trovato Salinaro A., Musso N., Medici V., et al. Expression of connexin 43 in the human epileptic and drug-resistant cerebral cortex. Neurology. 2011;76:895–902. doi: 10.1212/WNL.0b013e31820f2da6. [DOI] [PubMed] [Google Scholar]
  • [12].Condorelli D.F., Mudò G., Trovato-Salinaro A., Mirone M.B., Amato G., Belluardo N. Connexin-30 mRNA is up-regulated in astrocytes and expressed in apoptotic neuronal cells of rat brain following kainateinduced seizures. Mol Cell Neurosci. 2002;21:94–113. doi: 10.1006/mcne.2002.1155. [DOI] [PubMed] [Google Scholar]
  • [13].Condorelli D.F., Trovato-Salinaro A., Mudo G., Mirone M.B., Belluardo N. Cellular expression of connexins in the rat brain: neuronal localization, effects of kainate-induced seizures and expression in apoptotic neuronal cells. Eur J Neurosci. 2003;18:1807–1827. doi: 10.1046/j.1460-9568.2003.02910.x. [DOI] [PubMed] [Google Scholar]
  • [14].Szente M., Gajda Z., Said Ali K., Hermesz E. Involvement of electrical coupling in the in vivo ictal epileptiform activity induced by 4-Aminopyridine in the neocortex. Neuroscience. 2002;115:1067–1078. doi: 10.1016/S0306-4522(02)00533-X. [DOI] [PubMed] [Google Scholar]
  • [15].Collignon F., Wetjen N.M., Cohen-Gadol A.A., Cascino G.D., Parisi J., Meyer F.B., et al. Altered expression of connexin subtypes in mesial temporal lobe epilepsy in humans. J Neurosurg. 2006;105:77–87. doi: 10.3171/jns.2006.105.1.77. [DOI] [PubMed] [Google Scholar]
  • [16].Magnotti L.M., Goodenough D.A., Paul D.L. Deletion of oligodendrocyte Cx32 and astrocyte Cx43 causes white matter vacuolation, astrocyte loss and early mortality. Glia. 2011;59:1064–1074. doi: 10.1002/glia.21179. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • [17].Yao L.F., Wang Z.K., Wang Z.G., Sui D., Zhang L.M. Expression and function of Cx32 and Cx43 junctions in medically intractable temporal lobe epilepsy in human. Natl Med J Chin. 2009;89:3058–3060. [PubMed] [Google Scholar]
  • [18].Gajda Z., Gyengesi E., Hermesz E., Ali K.S., Szente M. Involvement of gap junctions in the manifestation and control of the duration of seizures in rats in vivo. Epilepsia. 2003;44:1596–1600. doi: 10.1111/j.0013-9580.2003.25803.x. [DOI] [PubMed] [Google Scholar]
  • [19].Zhang Y., Shan W., Zhang G. The relations between electrical synapse and the mechanism of epilepsy in genetically epilepsy-prone rat. Ntal Med J Chin. 1998;78:311–313. [PubMed] [Google Scholar]
  • [20].Racine R.J. Modification of seizure activity by electrical stimulation. II. Motor seizure. Electroencephalogr Clin Neurophysiol. 1972;32:281–294. doi: 10.1016/0013-4694(72)90177-0. [DOI] [PubMed] [Google Scholar]
  • [21].Ausubel F.M., Brent R., Kingston R.E., Moore D.D., Seidman J.G., Smith J.A., et al. Short Protocols in Molecular Biology. 5th ed. New York: Wiley; 2002. [Google Scholar]
  • [22].Livak K.J., Schmittgen T.D. Analysis of relative gene expression data using real-time quantitative PCR and the 2(-Delta Delta C (T)) Method. Methods. 2001;25:402–408. doi: 10.1006/meth.2001.1262. [DOI] [PubMed] [Google Scholar]
  • [23].Vaerman J.L., Saussoy P., Ingargiola I. Evaluation of real-time PCR data. J Biol Regul Homeost Agents. 2004;18:212–214. [PubMed] [Google Scholar]
  • [24].Kielian T. Glial connexins and gap junctions in CNS inflammation and disease. J Neurochem. 2008;106:1000–1016. doi: 10.1111/j.1471-4159.2008.05405.x. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • [25].Temme A., Traub O., Willecke K. Downregulation of connexin32 protein and gap-junctional intercellular communication by cytokine-mediated acute-phase response in immortalized mouse hepatocyte. Cell Tissue Res. 1998;294:345–350. doi: 10.1007/s004410051184. [DOI] [PubMed] [Google Scholar]
  • [26].Rouach N., Calvo C.F., Glowinski J., Giaume C. Brain macrophages inhibit gap junctional communication and downregulate connexin 43 expression in cultured astrocytes. Eur J Neurosci. 2002;15:403–447. doi: 10.1046/j.0953-816x.2001.01868.x. [DOI] [PubMed] [Google Scholar]
  • [27].Nagy J.I., Patel D., Ochalski P.A.Y., Stelmack G.L. Connexin 30 in rodent, cat and human brain: selective expression in gray matter astrocytes, co-localization with connexin43 at gap junctions and late developmental appearance. Neuroscience. 1999;88:447–468. doi: 10.1016/S0306-4522(98)00191-2. [DOI] [PubMed] [Google Scholar]
  • [28].Rouach N., Koulakoff A., Abudara V., Willecke K., Giuame C. Astroglial metabolic networks sustain synaptic transmission. Science. 2008;322:1551–1555. doi: 10.1126/science.1164022. [DOI] [PubMed] [Google Scholar]
  • [29].Gosejacob D., Dublin P., Bedner P. Role of astroglial connexin30 in hippocampal gap junction coupling. Glia. 2011;59:511–519. doi: 10.1002/glia.21120. [DOI] [PubMed] [Google Scholar]
  • [30].Wallraff A., Köhling R., Hinemann U., Theis M., Willecke K., Steinhauser C. The impact of astrocytic gap junctional coupling on potassium buffering in the hippocampus. J Neurosci. 2006;26:5438–5447. doi: 10.1523/JNEUROSCI.0037-06.2006. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • [31].Bennet S.A.L., Arnold J.M., Chen J., Stenger J., Paul D.L., Roberts D.C.S. Long-term changes in connexin32 gap junction protein and mRNA expression following cocaine self-administration in rats. Eur J Neurosci. 1999;11:3329–3338. doi: 10.1046/j.1460-9568.1999.00752.x. [DOI] [PubMed] [Google Scholar]
  • [32].Oguro K., Jover T., Tanaka H., Lin Y., Kojima T., Oguro N., Grooms S.Y., Bennet M.V.L., Zukin R.S. Global ischemia-induced increases in the gap junctional proteins connexin32 (Cx32) and Cx36 in hippocampus and enhanced vulnerability of Cx32 knock-out mice. J Neurosci. 2001;21:7534–7542. doi: 10.1523/JNEUROSCI.21-19-07534.2001. [DOI] [PMC free article] [PubMed] [Google Scholar]

Articles from Neuroscience Bulletin are provided here courtesy of Springer

RESOURCES