- Email: [email protected]
Ontogeny of spontaneous petit mal-like seizures in Wistar rats
Developmental Brain Research, 30 (1986) 85-87 Elsevier
85
BRD 60164
Short Communications Ontogeny of spontaneous petit mal-like seizures in Wistar rats MARGUERITE VERGNES l , CHRISTIAN MARESCAUX2, ANTOINE DEPAULIS 1, GABRIEL MICHELETTI2 and JEAN-MARIE WARTER2 Groupe de Recherche d'Epilepsie Exp~rimentale 1Centrede Neurochimie du CNRS, and 2Clinique Neurologique C.H. U,, Strasbourg (France) (Accepted 3 June 1986) Key words: Electroencephalogram (EEG) - - Rat - - Genetic epilepsy - - Spontaneous petit mal - - Ontogeny
Wistar rats spontaneously presenting electroclinical signs of petit mal-like epileptic seizures were inbred until all offspring were affected, and the ontogeny of this inherited phenotype was studied in the offspring from 30-60 days of age to 18 months. The first EEG spike and wave discharges appeared at 40-120 days. Their number and duration increased progressively with age. Spontaneous and recurrent paroxysmal electroencephalogram ( E E G ) discharges have been recorded in various rodents (for review see refs. 4, 17) and in Wistar rats in our breeding colony 8'9'17. The E E G pattern in these rats appears to correspond to petit mal epileptic seizures. Discharges lasting from a few to several dozens of seconds consist of bilateral, synchronous spike-waves, predominantly anterior, 7 - 1 0 c/s, 250-800 ¢tV in amplitude, superimposed on a normal background rhythm. They occur in the calm, awake state and are accompanied by immobility and clonus of the facial and cervical muscles 9A7. The electroclinical seizures are selectively suigpressed by those antiepileptics efficacious against petit real in man, whereas antiepileptics specific for focal or convulsive seizures are ineffective s'l°. Finally, these discharges are aggravated by all drugs inducing or aggravating petit mal absences in other animal models: pentylenetetrazol (PTZ) 8, y-aminobutyric acid ( G A B A ) mimetics ts, and also by penicillin, opiates and ~,-hydroxybutyrate (unpublished results). The petit mal-like seizures in the rats of our colony are determined genetically. By the third generation of crosses between affected rats, all offspring present the characteristic E E G 9. By the third generation of
crosses between unaffected rats, no offspring are affected (unpublished results). In our past experiments we have used only adult rats 4 months old or older. Here we have followed the ontogeny and spontaneous development of the E E G paroxystic discharges which characterize the petit maMike seizures in our Wistar rats. Twenty-four young Wistar rats, 12 males and 12 females, from the 6th and 7th generation of rats inbred for spike-wave E E G discharges, and 16 rats, 10 males and 6 females, from the 4th generation of outbred rats, age 3 0 - 6 0 days, were anesthetized with pentobarbital 40 mg/kg i.p., and fitted with two extradural monopolar electrodes placed over the right frontoparietal cortex (for details see ref. 17). Twenty-two of the rats lost their connector 1-11 months later. The wounds were disinfected and sutured. Electrodes were reimplanted later if the rats were in good condition. Ten epileptic and 12 non-epileptic rats were followed to the age of 18 months. During recording sessions, the freely moving animals were placed in individual Plexiglas cages. After a 15-min habituation period, the E E G was recorded for 1 h. The animals were observed and kept awake if necessary. The recordings started one day after elec-
Correspondence: M. Vergnes. Laboratoire de Neurophysiologie, Centre de Neurochimie du CNRS, 5 rue Blaise Pascal 67084 Strasbourg C6dex, France. 0165-3806/86/$03.50 © 1986 Elsevier Science Publishers B.V. (Biomedical Division)
86 trode implantation. They were r e p e a t e d every 10 days until the age of 4 months, and then every m o n t h until the age of 18 months. The recordings were analyzed visually for highamplitude paroxysmal discharges s u p e r i m p o s e d on an unsynchronized waking pattern. The frequency of the spike-wave discharges and their n u m b e r and duration were counted. In rats bred for spike-waves, the E E G discharges a p p e a r e d at 40-120 days of age, usually around 60
&
50
~ .
~
.
,
~
~
~
~
.~. ~.~ ~
,
~
.
~
seizures start in Wistar rats as early as 11/2 months of age, most often around 2 months, sometimes later. In rat models of petit mal induced by different drugs, in particular y-hydroxybutyrate and leucine e n k e p h alin 13'15, fully d e v e l o p e d seizures start from 4 weeks of age on. The maturation of rat's cortical and subcortical electrogenesis is complete by 14 days 14. Thus, whereas focal and convulsive seizures can be induced in rats 5-15 days old 2'11'16, petit mal is an epilepsy of adult rats. Ethosuximide, the main antiabsence drug, has no antiepileptic action on the young rat, but is effective in various adult rat models of epilepsy 7,
..~.,.,~,.~
B 60
17 9s~ ---
.
.-
--...~
,
l r ~ t l l l [lmlll,r ~ . . . . . . .
!0261E
90
120
Z 22. °Z_ 27'_"2
,,o
days (Fig. 1; Table I). A t first, they were rare, 1 o i 2 per h, brief, 1 - 3 s, with a low spike-wave frequency, 4 - 5 c/s. Thereafter the number and duration of discharges and the spike-wave frequency increased progressively. The mean n u m b e r of E E G seizures reached a m a x i m u m of 50 per h at about 6 months of age; the mean duration increased to 20 s by 18 months of age, and the frequency of spike-waves was highest, 8 c/s, by about 4 months, The 16 rats outbred for seizures p r e s e n t e d none up to the end of the exp e r i m e n t at 18 months of age. In the rat, experimentally induced partial or generalized convulsive seizures vary as a function of age 1'2'11'16. In our colony, spontaneous petit mal-like
,-:.:z.-., 2s.--.-I 2oopv
Fig. 1. Ontogeny of EEG seizures in 3 different rats. On the
left, age of the animals in days.
The increased duration and n u m b e r of seizures might be the consequence of neurochemical modifications with development. A decrease of d o p a m i n e r -
TABLE I Spontaneous petit real-like EEG seizures in rats as a function of age Age days 30
40
50
60
90
120
10
14
18
24
16
14
0 0
4 28
7 38
17 70
14 87
14 100
150
180
270
360
450
540
10
6
6
10
10
7
9 90
6 100
6 100
10 100
10 100
7 100
Rats tested n
Rats with seizures n
% Seizures per h mean range Seizure duration (s) mean range Spike-wave frequency (c/s) mean range
2 1-3
2.5 1-4
9 1-45
12.5 2-64
2 1-3
2.5 1-3
2.4 1-6
2.1 1-5
2.6 1-5
4.5 4-5
5 4.5-5
5 4.5-6.5
6.5 4-7.5
7.5 5-8.5
27 37 4-63 14-75
53 30-86
50 15-75
59 56 30-100 30-98
53 31-70
3.2 2-6
4 2-8
5.8 2-13
10.6 3-35
13.5 3-40
19.6 7-40
8 7-8.5
8 7-9
8.5 7-9
8 7-9
8.5 8-9
8.5 8-9
87 gic and n o r a d r e n e r g i c activity favors the a p p e a r a n c e of petit mal-like seizures in rodents 5'6. L o n g e r sei-
It is important to be aware of the spontaneous dev e l o p m e n t p a t t e r n of petit mal-like seizures in the rat
zures might also be associated with the level of activity and vigilance. S p o n t a n e o u s seizures are seen only in awake, immobile, calm animals, and are interr u p t e d as soon as the rat responds to any sensory stimulus 17. The vigilant yet inattentive and inactive state, rare in young animals, is the rule in older ones. Petit mal seizures are most easily induced during p r e p u b e r t y in the p r i m a t e 12 and in certain cat models 3, unlike the rat. In man, petit mal epilepsy is a disease of childhood which tends to d i s a p p e a r at puberty or adulthood. Since the m a t u r a t i o n of man's cortical and subcortical electrogenesis differs profoundly from those of the rat, it is not surprising that the ontogeny of petit mal epilepsy is quite unalike in the two species.
when chronic experiments are done. E E G patterns identical to those we have o b s e r v e d have been described following various brain lesions (for review see ref. 17). In long-term studies, the role of develo p m e n t may have been u n d e r e s t i m a t e d by comparison with that of the e x p e r i m e n t a l p r o c e d u r e itself. In conclusion, certain rats develop petit mal-like electroclinical seizures during early adulthood. The frequency of spike-waves and the n u m b e r of E E G discharges reach their final value at 5 - 6 months of age whereas duration of discharges increases progressively with age.
1 Chocholov~i, L. and Kolinov~i, M., Rhythmic activity of the awake phase in the rat, Activ. Nerv. Sup., 21 (1979) 36-38. 2 Gilbert, M.E. and Cain, D.P., A developmental study of kindling in the rat, Dev. Brain Res., 2 (1982) 321-328. 3 Guerrero-Figueroa, R., Barros, A., De Balbian Verster, F. and Heath, R.G., Experimental 'petit mal' in kittens, Arch. Neurol., 9 (1963) 297-306. 4 Kaplan, B.J., The epileptic nature of rodent electrocortical polyspiking is still unproven, Exp. Neurol., 88 (1985) 425-436. 5 King, G.A. and Burnham, W.M., a2-Adrenergic antagonists suppress epileptiform EEG activity in a petit real seizure model, Life Sci., 30 (1982) 293-298. 6 Kleinlogel, H., Spontaneous EEG paroxysms in the Rat: effects of psychotropic and alpha-adrenergic agonists, Neuropsychology, 13 (1985) 206-213. 7 Mares, P., Rokyta, R. and Trojan, S., Epileptic seizures during ontogenesis in the rat, J. Physiol. (Paris), 78 (1982-1983) 863-864. 8 Marescaux, C., Micheletti, G., Vergnes, M., Depaulis, A., Rumbach, L. and Warter, J.M., A model of chronic spontaneous petit mal-like seizures in the rat: comparison with pentylenetetrazol-induced seizures, Epilepsia, 25 (1984) 326-331. 9 Marescaux, C., Vergnes, M., Micheletti, G., Depaulis, A., Reis, J., Rumbach, L., Warter, J.M. and Kurtz, D., Une forme g6n6tique d'absences petit mal chez le rat Wistar, Rev. Neurol. (Paris), 140 (1984) 63-66. 10 Micheletti, G., Vergnes, M., Marescaux, C., Reis, J., Depaulis, A., Rumbach, L. and Warter, J.M., Antiepileptic drug evaluation in a new animal model: spontaneous petit
mal epilepsy in the rat, Arzneim. Forsch./Drug Res., 35 (1985) 483-485. 11 Mosh6, S.L. and Albala, B.J., Maturational changes in postictal refractoriness and seizure susceptibility in developing rats, Ann. Neurol., 13 (1983) 552-557. 12 Snead, O.C., Gamma hydroxybutyrate in the monkey. I. Electroencephalographic, behavioral and pharmacokinetic study, Neurology, 28 (1978) 636-642. 13 Snead, O.C., Ontogeny of y-hydroxybutyrate acid. II. Electroencephalographic effects, Dev. Brain Res., 15 (1984) 89-96. 14 Snead, O.C. and Stephens, H.I., Ontogeny of cortical and subcortical electroencephalographic events in unrestrained neonatal and infant rats, Exp. Neurol., 82 (1983) 249-269. 15 Snead, O.C. and Stephens, H., The ontogeny of seizures induced by leucine-enkephalin and fl-endorphin, Ann. Neurol., 15 (1984) 594-598. 16 Staudacherov~, D., Mar~s, P., Koz~kov~, H. and Camutaliov~, M., Ontogenic development of acetylcholine and atropine epileptogenic cortical loci in rats, Neuroscience, 3 (1978) 749-753. 17 Vergnes, M., Marescaux, C., Micheletti, G., Reis, J., Depaulis, A., Rumbach, L. and Wafter, J.M., Spontaneous paroxysmal electroclinical patterns in rat: a model of generalized non-convulsive epilepsy, Neurosci. Lett., 33 (1982) 97-101. 18 Vergnes, M., Marescaux, C., Micheletti, G., Depaulis, A., Rumbach, L. and Warter, J.M., Enhancement of spike and wave discharges by GABA-mimetic drugs in rats with spontaneous petit real-like epilepsy, Neurosci. Lett., 44 (1984) 91-94.
This article was translated from the F r e n c h by Sarah Dejours.
85
BRD 60164
Short Communications Ontogeny of spontaneous petit mal-like seizures in Wistar rats MARGUERITE VERGNES l , CHRISTIAN MARESCAUX2, ANTOINE DEPAULIS 1, GABRIEL MICHELETTI2 and JEAN-MARIE WARTER2 Groupe de Recherche d'Epilepsie Exp~rimentale 1Centrede Neurochimie du CNRS, and 2Clinique Neurologique C.H. U,, Strasbourg (France) (Accepted 3 June 1986) Key words: Electroencephalogram (EEG) - - Rat - - Genetic epilepsy - - Spontaneous petit mal - - Ontogeny
Wistar rats spontaneously presenting electroclinical signs of petit mal-like epileptic seizures were inbred until all offspring were affected, and the ontogeny of this inherited phenotype was studied in the offspring from 30-60 days of age to 18 months. The first EEG spike and wave discharges appeared at 40-120 days. Their number and duration increased progressively with age. Spontaneous and recurrent paroxysmal electroencephalogram ( E E G ) discharges have been recorded in various rodents (for review see refs. 4, 17) and in Wistar rats in our breeding colony 8'9'17. The E E G pattern in these rats appears to correspond to petit mal epileptic seizures. Discharges lasting from a few to several dozens of seconds consist of bilateral, synchronous spike-waves, predominantly anterior, 7 - 1 0 c/s, 250-800 ¢tV in amplitude, superimposed on a normal background rhythm. They occur in the calm, awake state and are accompanied by immobility and clonus of the facial and cervical muscles 9A7. The electroclinical seizures are selectively suigpressed by those antiepileptics efficacious against petit real in man, whereas antiepileptics specific for focal or convulsive seizures are ineffective s'l°. Finally, these discharges are aggravated by all drugs inducing or aggravating petit mal absences in other animal models: pentylenetetrazol (PTZ) 8, y-aminobutyric acid ( G A B A ) mimetics ts, and also by penicillin, opiates and ~,-hydroxybutyrate (unpublished results). The petit mal-like seizures in the rats of our colony are determined genetically. By the third generation of crosses between affected rats, all offspring present the characteristic E E G 9. By the third generation of
crosses between unaffected rats, no offspring are affected (unpublished results). In our past experiments we have used only adult rats 4 months old or older. Here we have followed the ontogeny and spontaneous development of the E E G paroxystic discharges which characterize the petit maMike seizures in our Wistar rats. Twenty-four young Wistar rats, 12 males and 12 females, from the 6th and 7th generation of rats inbred for spike-wave E E G discharges, and 16 rats, 10 males and 6 females, from the 4th generation of outbred rats, age 3 0 - 6 0 days, were anesthetized with pentobarbital 40 mg/kg i.p., and fitted with two extradural monopolar electrodes placed over the right frontoparietal cortex (for details see ref. 17). Twenty-two of the rats lost their connector 1-11 months later. The wounds were disinfected and sutured. Electrodes were reimplanted later if the rats were in good condition. Ten epileptic and 12 non-epileptic rats were followed to the age of 18 months. During recording sessions, the freely moving animals were placed in individual Plexiglas cages. After a 15-min habituation period, the E E G was recorded for 1 h. The animals were observed and kept awake if necessary. The recordings started one day after elec-
Correspondence: M. Vergnes. Laboratoire de Neurophysiologie, Centre de Neurochimie du CNRS, 5 rue Blaise Pascal 67084 Strasbourg C6dex, France. 0165-3806/86/$03.50 © 1986 Elsevier Science Publishers B.V. (Biomedical Division)
86 trode implantation. They were r e p e a t e d every 10 days until the age of 4 months, and then every m o n t h until the age of 18 months. The recordings were analyzed visually for highamplitude paroxysmal discharges s u p e r i m p o s e d on an unsynchronized waking pattern. The frequency of the spike-wave discharges and their n u m b e r and duration were counted. In rats bred for spike-waves, the E E G discharges a p p e a r e d at 40-120 days of age, usually around 60
&
50
~ .
~
.
,
~
~
~
~
.~. ~.~ ~
,
~
.
~
seizures start in Wistar rats as early as 11/2 months of age, most often around 2 months, sometimes later. In rat models of petit mal induced by different drugs, in particular y-hydroxybutyrate and leucine e n k e p h alin 13'15, fully d e v e l o p e d seizures start from 4 weeks of age on. The maturation of rat's cortical and subcortical electrogenesis is complete by 14 days 14. Thus, whereas focal and convulsive seizures can be induced in rats 5-15 days old 2'11'16, petit mal is an epilepsy of adult rats. Ethosuximide, the main antiabsence drug, has no antiepileptic action on the young rat, but is effective in various adult rat models of epilepsy 7,
..~.,.,~,.~
B 60
17 9s~ ---
.
.-
--...~
,
l r ~ t l l l [lmlll,r ~ . . . . . . .
!0261E
90
120
Z 22. °Z_ 27'_"2
,,o
days (Fig. 1; Table I). A t first, they were rare, 1 o i 2 per h, brief, 1 - 3 s, with a low spike-wave frequency, 4 - 5 c/s. Thereafter the number and duration of discharges and the spike-wave frequency increased progressively. The mean n u m b e r of E E G seizures reached a m a x i m u m of 50 per h at about 6 months of age; the mean duration increased to 20 s by 18 months of age, and the frequency of spike-waves was highest, 8 c/s, by about 4 months, The 16 rats outbred for seizures p r e s e n t e d none up to the end of the exp e r i m e n t at 18 months of age. In the rat, experimentally induced partial or generalized convulsive seizures vary as a function of age 1'2'11'16. In our colony, spontaneous petit mal-like
,-:.:z.-., 2s.--.-I 2oopv
Fig. 1. Ontogeny of EEG seizures in 3 different rats. On the
left, age of the animals in days.
The increased duration and n u m b e r of seizures might be the consequence of neurochemical modifications with development. A decrease of d o p a m i n e r -
TABLE I Spontaneous petit real-like EEG seizures in rats as a function of age Age days 30
40
50
60
90
120
10
14
18
24
16
14
0 0
4 28
7 38
17 70
14 87
14 100
150
180
270
360
450
540
10
6
6
10
10
7
9 90
6 100
6 100
10 100
10 100
7 100
Rats tested n
Rats with seizures n
% Seizures per h mean range Seizure duration (s) mean range Spike-wave frequency (c/s) mean range
2 1-3
2.5 1-4
9 1-45
12.5 2-64
2 1-3
2.5 1-3
2.4 1-6
2.1 1-5
2.6 1-5
4.5 4-5
5 4.5-5
5 4.5-6.5
6.5 4-7.5
7.5 5-8.5
27 37 4-63 14-75
53 30-86
50 15-75
59 56 30-100 30-98
53 31-70
3.2 2-6
4 2-8
5.8 2-13
10.6 3-35
13.5 3-40
19.6 7-40
8 7-8.5
8 7-9
8.5 7-9
8 7-9
8.5 8-9
8.5 8-9
87 gic and n o r a d r e n e r g i c activity favors the a p p e a r a n c e of petit mal-like seizures in rodents 5'6. L o n g e r sei-
It is important to be aware of the spontaneous dev e l o p m e n t p a t t e r n of petit mal-like seizures in the rat
zures might also be associated with the level of activity and vigilance. S p o n t a n e o u s seizures are seen only in awake, immobile, calm animals, and are interr u p t e d as soon as the rat responds to any sensory stimulus 17. The vigilant yet inattentive and inactive state, rare in young animals, is the rule in older ones. Petit mal seizures are most easily induced during p r e p u b e r t y in the p r i m a t e 12 and in certain cat models 3, unlike the rat. In man, petit mal epilepsy is a disease of childhood which tends to d i s a p p e a r at puberty or adulthood. Since the m a t u r a t i o n of man's cortical and subcortical electrogenesis differs profoundly from those of the rat, it is not surprising that the ontogeny of petit mal epilepsy is quite unalike in the two species.
when chronic experiments are done. E E G patterns identical to those we have o b s e r v e d have been described following various brain lesions (for review see ref. 17). In long-term studies, the role of develo p m e n t may have been u n d e r e s t i m a t e d by comparison with that of the e x p e r i m e n t a l p r o c e d u r e itself. In conclusion, certain rats develop petit mal-like electroclinical seizures during early adulthood. The frequency of spike-waves and the n u m b e r of E E G discharges reach their final value at 5 - 6 months of age whereas duration of discharges increases progressively with age.
1 Chocholov~i, L. and Kolinov~i, M., Rhythmic activity of the awake phase in the rat, Activ. Nerv. Sup., 21 (1979) 36-38. 2 Gilbert, M.E. and Cain, D.P., A developmental study of kindling in the rat, Dev. Brain Res., 2 (1982) 321-328. 3 Guerrero-Figueroa, R., Barros, A., De Balbian Verster, F. and Heath, R.G., Experimental 'petit mal' in kittens, Arch. Neurol., 9 (1963) 297-306. 4 Kaplan, B.J., The epileptic nature of rodent electrocortical polyspiking is still unproven, Exp. Neurol., 88 (1985) 425-436. 5 King, G.A. and Burnham, W.M., a2-Adrenergic antagonists suppress epileptiform EEG activity in a petit real seizure model, Life Sci., 30 (1982) 293-298. 6 Kleinlogel, H., Spontaneous EEG paroxysms in the Rat: effects of psychotropic and alpha-adrenergic agonists, Neuropsychology, 13 (1985) 206-213. 7 Mares, P., Rokyta, R. and Trojan, S., Epileptic seizures during ontogenesis in the rat, J. Physiol. (Paris), 78 (1982-1983) 863-864. 8 Marescaux, C., Micheletti, G., Vergnes, M., Depaulis, A., Rumbach, L. and Warter, J.M., A model of chronic spontaneous petit mal-like seizures in the rat: comparison with pentylenetetrazol-induced seizures, Epilepsia, 25 (1984) 326-331. 9 Marescaux, C., Vergnes, M., Micheletti, G., Depaulis, A., Reis, J., Rumbach, L., Warter, J.M. and Kurtz, D., Une forme g6n6tique d'absences petit mal chez le rat Wistar, Rev. Neurol. (Paris), 140 (1984) 63-66. 10 Micheletti, G., Vergnes, M., Marescaux, C., Reis, J., Depaulis, A., Rumbach, L. and Warter, J.M., Antiepileptic drug evaluation in a new animal model: spontaneous petit
mal epilepsy in the rat, Arzneim. Forsch./Drug Res., 35 (1985) 483-485. 11 Mosh6, S.L. and Albala, B.J., Maturational changes in postictal refractoriness and seizure susceptibility in developing rats, Ann. Neurol., 13 (1983) 552-557. 12 Snead, O.C., Gamma hydroxybutyrate in the monkey. I. Electroencephalographic, behavioral and pharmacokinetic study, Neurology, 28 (1978) 636-642. 13 Snead, O.C., Ontogeny of y-hydroxybutyrate acid. II. Electroencephalographic effects, Dev. Brain Res., 15 (1984) 89-96. 14 Snead, O.C. and Stephens, H.I., Ontogeny of cortical and subcortical electroencephalographic events in unrestrained neonatal and infant rats, Exp. Neurol., 82 (1983) 249-269. 15 Snead, O.C. and Stephens, H., The ontogeny of seizures induced by leucine-enkephalin and fl-endorphin, Ann. Neurol., 15 (1984) 594-598. 16 Staudacherov~, D., Mar~s, P., Koz~kov~, H. and Camutaliov~, M., Ontogenic development of acetylcholine and atropine epileptogenic cortical loci in rats, Neuroscience, 3 (1978) 749-753. 17 Vergnes, M., Marescaux, C., Micheletti, G., Reis, J., Depaulis, A., Rumbach, L. and Wafter, J.M., Spontaneous paroxysmal electroclinical patterns in rat: a model of generalized non-convulsive epilepsy, Neurosci. Lett., 33 (1982) 97-101. 18 Vergnes, M., Marescaux, C., Micheletti, G., Depaulis, A., Rumbach, L. and Warter, J.M., Enhancement of spike and wave discharges by GABA-mimetic drugs in rats with spontaneous petit real-like epilepsy, Neurosci. Lett., 44 (1984) 91-94.
This article was translated from the F r e n c h by Sarah Dejours.