Abstract
A sensitive method of estimation of generalized seizure thresholds (GSTs) was used to estimate the relative anticonvulsant potencies of four competitive NMDA antagonists against fully amygdala-kindled seizures. All of the antagonists tested showed potent, dose-dependent anticonvulsant activity following focal administration at doses causing no, or only minimal, overt behavioural abnormalities. These doses were similar to those which have previously been shown to inhibit the development of the kindling process i.e. which show antiepileptogenic activity. Two novel, competitive NMDA antagonists, CGP 37849 and CGP 39551, both unsaturated analogues of the NMDA antagonist AP5, showed by far the greatest anticonvulsant potencies (211-fold and 33-fold greater activity than the parent molecule, respectively). Recent reports of oral anticonvulsant activity of these two compounds in both rodent and primate models of epilepsy (12, 13) make them leading candidates for clinical testing as novel antiepileptic agents in man. Previous reports of weak or non-existent anticonvulsant activity of competitive NMDA antagonists in the kindling model of epilepsy most likely result from the use of experimental protocols which are inherently insensitive in detecting drug-induced changes in seizure thresholds.
Similar content being viewed by others
References
Albright, P. S., and Burnham, W. M. 1980. Development of a new pharmacological seizure model: effects of anticonvulsants on cortical- and amygdala-kindled seizures in the rat. Epilepsia 21:681–689.
McNamara, J. O. 1984. Kindling: an animal model of complex partial epilepsy. Ann. Neurol. 16(suppl.):572–576.
Goddard, G. V. McIntyre, D. C., and Leech, C. K. 1969. A permanent change in brain function resulting from daily electrical stimulation. Exp. Neurol. 25:295–330.
Croucher, M. J., Bradford, H. F., Sunter, D. C., and Watkins, J. C. 1988. Inhibition of the development of electrical kindling of the prepyriform cortex by daily focal injections of excitatory amino acid antagonists. Eur. J. Pharmacol. 152:29–38.
Cain, D. P., Desborough, K. A., and McKitrick, D. J. 1988. Retardation of amygdala kindling by antagonism of NMD-aspartate and muscarinic cholinergic receptors: Evidence for the summation of excitatory mechanisms in kindling. Exp. Neurol. 100:179–187.
Slater, N. T., Stelzer, A., and Galvan M. 1985. Kindling-like stimulus patterns induce epileptiform discharges in the guinea-pigin vitro hippocampus. Neurosci. Lett. 60:25–31.
Stelzer, A., Slater, N. T. and ten Bruggencate, G. 1987. Activation of NMDA receptors blocks GABAergic inhibition in anin vitro model of epilepsy. Nature 326:698–701.
Stasheff, S. F., Anderson, W. W., Clark S., and Wilson, W. A. 1989. NMDA antagonists differentiate epileptogenesis from seizure expression in anin vitro model. Science 245:648–651.
Peterson, D. W., Collins, J. F., and Bradford, H. F. 1983. The kindled amygdala model of epilepsy: anticonvulsant action of amino acid antagonists. Brain Res. 275:169–172.
Peterson, D. W., Collins, J. F., and Bradford, H. F. 1984. Anticonvulsant action of amino acid antagonists against kindled hippocampal seizures. Brain Res. 311:176–180.
Pozza, M. F., Olpe, H.-R., Brugger, F. and Fagg, G. E. 1990. Electrophysiological characterization of a novel potent and orally active NMDA receptor antagonist: CGP 37849 and its ethylester CGP 39551. Eur. J. Pharmacol. 182:91–100.
Fagg, G. E., Olpe, H.-R., Pozza, M. F., Band, J., Steinmann, M., Schmutz, M., Hortet C., Baumann, P., Thedinga, K., Bittiger, H., Allgeier, H., Heckendorn, R., Angst, C. Brundish, D., and Dingwall, J. G. 1990. CGP 37849 and CGP 39551: novel and potent competitive N-methyl-D-aspartate receptor antagonists with oral activity. Br. J. Pharmacol. 99:791–797.
Schmutz, M., Portet C., Jeker, A., Klebs, K., Vassout, A., Allgeier, H., Heckendorn, R., Fagg, G. E., Olpe, H.-R., and van Riejen, H. 1990. The competitive NMDA receptor antagonists CGP 37849 and CGP 39551 are potent, orally-active anticonvulsants in rodents. Naunyn-Schmied. Arch. Pharmacol. 342:61–66.
Cotterell, K. L., Croucher, M. J., and Bradford, H. F. 1991. CGP 37849 and CGP 39551 raise generalized seizure thresholds in the amygdala kindling model of epilepsy. Fund. Clin. Pharmacol. 5(5):444.
Croucher, M. J., and Bradford, H. F. 1989. Kindling of full limbic seizures by repeated microinjections of excitatory amino acids into the rat amygdala. Brain. Res. 501:58–65.
Croucher, M. J., and Bradford, H. F. 1991. The influence of strychnine-insensitive glycine receptor agonists and antagonists on generalized seizure thresholds. Brain. Res. 543:91–96.
Freeman, F. G., and Jarvis, M. F. 1981. The effect of interstimulation interval on the assessment and stability of kindled seizure thresholds. Brain. Res Bull. 7:629–633.
Racine, R. J. 1972. Modification of seizure activity by electrical stimulation: II. Motor seizure. Electroenceph. Clin. Neurophysiol. 32:281–294.
Mucha, R. F., and Pinel, J. P. J. 1977. Postseizure inhibition of kindled seizures. Exp. Neurol. 54:266–282.
Croucher, M. J., and Bradford, H. F. 1990. NMDA receptor blockade inhibits glutamate-induced kindling of the rat amygdala. Brain Res. 506:349–352.
Freeman, F. G., Jarvis, M. F., and Duncan, P. M. 1982. Phencyclidine raises kindled seizure thresholds. Pharmacol. Biochem. Behav. 16:1009–1011.
Croucher, M. J., and Bradford, H. F. 1990b. 7-Chlorokynurenic acid, a strychnine-insensitive glycine receptor antagonist, inhibits limbic seizure kindling. Neurosci. Lett. 118:29–32.
Croucher, M. J., Collins, J. F., and Meldrum, B. S. 1982. Anticonvulsant action of excitatory amino acid antagonists. Science 216:899–901.
Meldrum, B. S., Croucher M. J., Czuczwar, S. I., Collins, J. F., Curry, K., Joseph, M., and Stone, T. W. 1984. A comparison of the anticonvulsant potency of 2-amino-5-phosphonopentanoic acid and 2-amino-7-phosphonoheptanoic acid. Neuroscience 9:925–930.
Tricklebank, M. D., Singh, L., Oles, R. J., Preston, C., and Iversen, S. D. 1989. The behavioural effects of MK-801: a comparison with antagonists acting non-competitively and competitively at the NMDA receptor. Eur. J. Pharmacol. 167:127–135.
Vezzani, A., Wu, H.-Q., Moneta, E., and Samanin, R. 1988. Role of the N-methyl-D-aspartate-type receptors in the development and maintenance of hippocampal kindling in rats Neurosci. Lett. 87:63–68.
Chapman, A. G., Collins, J. F., Meldrum, B. S., and Westerberg, E. 1983. Uptake of a novel anticonvulsant compound 2-amino-7-phosphono-[4,5-3H]-heptanoic acid, into mouse brain. Neurosci. Lett. 37:75–80.
Author information
Authors and Affiliations
Additional information
Special issue dedicated to Dr. Morris H. Aprison.
Rights and permissions
About this article
Cite this article
Croucher, M.J., Cotterell, K.L. & Bradford, H.F. Competitive NMDA receptor antagonists raise electrically kindled generalized seizure thresholds. Neurochem Res 17, 409–413 (1992). https://doi.org/10.1007/BF00969885
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF00969885