Neurotransmitters in Epilepsy. Epilepsy Research Supplements, Volume 8

388 Pages·1992·10.948 MB·English

by  Giuliano Avanzini, J. Engel, R. Fariello and U. Heinemann (Eds.)

Neurotransmitters
in Epilepsy
EDITED BY
GIULIANO AVANZINI
National Neurological Institute C. Besta, Milan, Italy
JEROME ENGEL Jr.
Reed Neurological Research Center, UCLA School of Medicine, Los Angeles,
CA, USA
RUGGERO FARIELLO
Erbamont Research and Development Neurobiology Program, Nerviano, Milan, Italy
UWE HEINEMANN
Institute of Neurophysiology, University of Cologne, Cologne, Germany
EPILEPSY RESEARCH
SUPPLEMENT NO. 8
1992
ELSEVIER
AMSTERDAM - LONDON - NEW YORK - TOKYO
Epilepsy Res., 1992, Suppl. 8
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V
Dedication
This book is dedicated to Herbert H. Jasper, portrayed here receiving the Carlo
Besta Prize from Eugenio Maccari, Councillor of the Regione Piemonte.
The first Carlo Besta prize was awarded to Herbert H. Jasper in recognition of his
outstanding contribution to the founding and development of modern epileptology.
The prize was established to honor Carlo Besta (1876-1940), an Italian pioneer in the
study of neurobiology of epilepsy and founder of the National Neurological Institute
of Milano.
Dr. Franco Arosio, Managing Director
Carlo Besta National Neurological Institute
vii
Foreword
This book represents the latest in a series of monographs emanating from Work-
shops on Neurotransmitters in Epilepsy, held under the aegis of the International
League Against Epilepsy (ILAE). It summarizes the neurophysiological, neurochem-
ical, and neuropharmacological state of the art in epilepsy research in the area of
neurotransmitter function. It is right and proper that Herbert Jasper wrote the intro-
duction, since he was present at the dawning of the GABA era and has watched this
inhibitory neurotransmitter assume its place in the overall scheme of things.
It is this overall scheme of things that makes up the core of the book, which con-
tains sections on neurotransmitter physiology, experimental models, and GABA
mechanisms as well as a section on excitatory amino acids, which hold center stage
at this time in epilepsy-related neurotransmitter pharmacology. A section on other
neurotransmitters rounds out this topic.
A section on chronic models and human epilepsy emphasizes the application of
basic research epilepsy to the human condition.
Preparation of this volume coincides with the development of the Commission on
Neurobiology of Epilepsy of the ILAE. The Commission will bear testimony to a
major goal of the League's activity, which is the integration of basic science research
into all the areas of ILAE activities as proposed by the Commission on Long-Range
Planning. This allows the basic researchers in neurophysiology, neuropharmacology,
neurochemistry, and neurogenetics to find a focus of integration in the epilepsy
movement with the clinically relevant sciences that constitute epileptology.
F.E. Dreifuss,
President, International League Against Epilepsy
ix
Preface
This volume presents recent information on the role of neurotransmitters in epilep-
togenesis. Herbert H. Jasper, to whom this book is dedicated, has written the intro-
ductory chapter tracing the development of neurochemical studies in epileptology.
The remainder of the volume is organized into five sections. The first section addres-
ses the various experimental models of epilepsy used for studying neurotransmitter
mechanisms and points out the importance of understanding the potential relation-
ships between these models and human epileptic phenomena. The second section is
concerned with the inhibitory neurotransmitter, gamma-aminobutyric acid (GABA).
Some forms of epileptic excitablility may reflect disinhibition due to depression in
GABA efficacy, while GABA-dependent hyperexcitability may result from inhibi-
tion of inhibitory neurons. GABA may also play an active role in the development
of hypersynchronous activity that underlies the appearance of epileptiform spike-
and-wave discharges. Several chapters deal with pharmacological and electrophysio-
logical investigations of anticonvulsant and convulsant actions of GABA at the
channel and receptor levels. The third section discusses studies that have led to new
insights into the role of excitatory amino acids in mediating epileptic phenomena.
Most of the papers deal with iV-methyl-D-aspartate (NMDA) versus non-NMDA
receptor involvement in epileptogenesis and with the resulting implications for the
development of new antiepileptic drugs. Reports of new methodological approaches
for assessing the functional activation of NMDA receptors deserve particular atten-
tion. The fourth section considers the possible anticonvulsant action of adenosine, as
well as the role of acetylcholine and noradrenaline in neuronal graft-dependent sup-
pression and induction of epileptic activity. The final section contains a series of re-
ports of investigations into the roles of various neurotransmitters in chronic animal
models of epilepsy, including genetic ones, as well as in human epilepsy.
Although many of the questions that arose during the workshop have been
answered by the authors in the context of their chapters, the book also includes an
abridged version of the spirited discussions on topics not specifically addressed in
individual papers. This discussion particularly emphasizes the multidisciplinary char-
acter of the book, which combines contributions from different fields of neuroscience
in an integrated approach to the neurobiology of the epilepsies.
Giuliano Avanzini
Jerome Engel, Jr.
Ruggero Fariello
Uwe Heinemann
X
Acknowledgements
The chapters of this book arise from the proceedings of the Fourth Workshop on
Neurotransmitters in Epilepsy (WONIEP IV), held in Stresa, Italy, during October
9-12, 1988, under the aegis of the International League Against Epilepsy (ILAE).
Many have been recently updated to reflect the most current information in the
field. The WONIEP conferences were conceived as a forum for neuroscientists from
many disciplines to exchange information on this important aspect of epileptic
mechanisms. Paolo Morselli deserves special credit for his key role in the develop-
ment of these workshops and their contribution to the field of epileptology.
WONIEP IV has been made possible by the generous support of the Assesserato
alia Sanita of the Regione Piemonte, which is gratefully acknowledged, with special
thanks to assessore Eugenio Maccari and to his collaborator, Dr. Luciano Frego.
Additional support was provided by Ciba-Geigy, Defitin, Knoll, Lepetit, Mad-
daus, Sigma-Tau, Suxil, Tiopoun, Valeas, Wellcome, and Dr. Willnar Schwabe.
These contributors are thanked for their sensitivity to this scientific initiative.
The publication of the present volume has been subsidized by Fondazione Pier-
franco e Luisa Mariani, Milano, Italy, which is gratefully acknowledged.
© 1992 Elsevier Science Publishers B. V. All rights reserved.
Neurotransmitters in Epilepsy (Epilepsy Res. Suppl. 8)
G. Avanzini, J. Engel Jr, R. Fariello, U. Heinemann (Eds) 1
Historical Introduction:
CHAPTER 1
Early efforts to find neurochemical mechanisms
in epilepsy
Herbert H. Jasper
Montreal, Canada
The belief that there must be a humoral basis for Oft too some wretch, before our startled sight,
epileptiform seizures has a very long and checkered Struck as by lightning, by some keen disease
Drops sudden,—by the dread attack o'erpowered
history, beginning with Hippocrates in his classic
He foams, he groans, he trembles and he faints,
treatise "On The Sacred Disease," written about 460
Now rigid, now convulsed, his laboring lungs
B.C. Penfield, in his comments on the history of
Heave quick, and quiver each exhausted limb,
epilepsy (Penfield and Erickson, 1941) quotes from
Spread through the frame, so deep the dire disease
Hippocrates as follows:
Perturbs his spirit: as the briny main
Foams through each wave beneath the tempest's ire
But when at length the sordid cause declines,
"Observe the goat," said Hippocrates, "for that animal
And the fermenting humors from the heart
is most prone to this disease. . . . Open the head and
Flow back—with staggering foot the man first treads,
you will find the brain wet bathed in a hydroptic fluid
Led gradual on to intellect and strength.
of evil odor; there you will find evidence that it is not
the divinity, but the disease that thus alters the body.
. . . And so it is with man. For when the disease has This ancient view that epileptic seizures were due
prevailed for a length of time, it is no longer curable, as to evil humors affecting the brain persisted for nearly
the brain is corroded by the phlegm, and melted, and 2,000 years before scientific evidence was provided
what is melted down becomes water, and surrounds the
in its support. The discovery of neurochemical trans-
brain externally, and overflows it. . .
mitter substances in the central nervous system, and
especially in the brain, is, of course, of very recent
Penfield adds that "our admiration for Hippocrates origin. It was only a little over 50 years ago when
is not dimmed by the fact that it was probably the Sir Henry Dale, Wilhelm Feldberg, and Marthe Vogt
goat that he smelled and not the brain, and that the were providing convincing evidence that acetylcho-
fluid may have been cerebrospinal fluid." line (Ach) was the neurotransmitter at the neuromus-
The prevailing view that there was a humoral cause cular junction and peripheral sympathetic ganglion.
of epileptiform seizures was apparent even in the I was able to share in the excitement of these
writings of the poet Lucretius (95-55 B.C.), also important developments by my tenure as a postdoc-
quoted by Penfield as follows: toral fellow in Paris during the early 1930s. We
2
visited Dale's laboratories and attended the meetings tical brain tissue, presumably due to its liberation
of the British Physiological Society, where there was during the convulsive discharge.
always a lively debate between Dale and Eccles, who It was soon shown that Ach in sufficiently high
was then defending the electrical and opposed to the concentrations is capable of producing epileptiform
chemical view of synaptic transmission. Neurophy- discharge when applied to the cerebral cortex, espe-
siologists were divided into two camps at this time, cially if the cortex is pretreated by an anticholines-
those defending "soup" and those following the terase such as eserine, or by longer acting drugs such
traditional "sparks" view of synaptic transmission. as DFP (Burgen and Macintosh, 1955; Stone, 1957).
It was only in the 1950s that Ach was shown to be a Such Ach-induced seizures were prevented by atro-
neurotransmitter in the spinal cord, and several years pine.
later the excitatory action of Ach in the brain was Tower and Elliott (1952, 1953) were able to show
demonstrated, and its possible involvement in epilep- an apparent defect in the ability of human focal
tiform seizures was shown. epileptogenic cortical tissue to bind Ach, which would
It was shown by Pope et al. in our laboratories in suggest an abnormality in Ach metabolism as one
Montreal immediately following the war (1947) that mechanism involved in human epileptogenic lesions,
there was a marked increase in acetylcholinesterase but these findings were not confirmed in later studies
in human focal epileptogenic cortical tissue excised by Pappius and Elliott (1958).
by Dr. Penfield during operations for focal epilepsy. We then developed a plastic cup that c2ould be
It was also found by the same authors that experi- screwed into the skull over about a 1-cm cortical
mental chronic epileptic foci produced by aluminum surface to make possible continuous superfusion and
cream in monkeys was associated with a marked collection of samples of extracellular fluid in animals
increase in acetylcholinesterase in a mirror focus in under various physiological conditions. If the cortex
the homologous area of the opposite hemisphere. The was treated by an anticholinesterase, such as eserine
Ach esterase returned to normal in the mirror focus or physostigmine, the rate of liberation of Ach from
after removal of the primary alumina cream focal the cortex could be measured (Fig. 1-1). This rate
area. was found to vary systematically with the level of
It would seem that the liberation of free Ach must arousal and sleep or light barbiturate anesthesia. Lo-
be involved in the epileptic process, with a reactive cal treatment of the cortical surface with eserine in
increase in Ach esterase, but it could have been either the resting animal caused a desynchronized activation
a cause or a result of the convulsive discharge. of the EEG locally, which was transformed into a
Richter and Crossland (1949) then found that seizures focal epileptic discharge by increased liberation of
induced in experimental animals by electrical stimu- Ach caused by electrical stimulation of the brainstem
lation or metrazol were associated with a marked reticular system, as shown in Fig. 1-2, from Celesia
reduction of the amount of Ach extracted from cor- and Jasper (1966). This shows that a defect in Ach
S R
Fig. 1-1. Diagram of superfusion cup sealed into
the skull over the pial surface of the cerebral
cortex for the collection of samples of extracel-
lular fluid for analysis of the liberation of trans-
mitters substances under different physiological
states. (Reproduced with permission from Ce-
lesia and Jasper, 1966.)
3
PO. SSTUP.R ASYLV
PO. SST. IG(C"U P)
t
o
u
o 31-
[20 5v»
1 cte
Fig. 1-2. In the "encephale isole" cat preparation, without general anesthesia, the superfusion cup is installed over the eserinized posterior
sigmoid gyrus for the collection of cortical superfusate bioassayed for concentration of ACh. Electrocorticograms were taken from within
the cup over the sigmoid gyrus as well as from the noneserinized suprasylvian gyrus. In a is shown the desynchronized activation of the
EG from eserinized cortex, which develops into focal epileptic discharge in b. The cortex is then treated with atropine, which arrests the
local epileptiform discharge in spite of increase in concentration of Ach, as shown in column graph on left. (Reproduced with permission
from Celesia and Jasper, 1966.)
inactivating mechanisms in cerebral cortex, which exposed cerebral cortex in the cat. Bursts of spikes
allows the accumulation of Ach to abnormal levels, and shifts in DC polarization of the cortex were
can result in a focal epileptic discharge that may be recorded with an extracellular microelectrode, with
prevented by atropine. It is important to note that the depolarizing inactivation occurring during prolonged
Ach in this model was liberated in the cortex by seizures, as shown in Fig. 1-3.
stimulation of the brainstem reticular system. Blocking of ACh-induced epileptic discharge with
In later microelectrode studies with John Ferguson atropine did not prevent activation of the same area
(Ferguson and Jasper, 1971), we were able to dem- of cortex by electrical stimulation or by metrazol.
onstrate the epileptiform activation of single cortical Curiously, atropine served to increase by severalfold
cells, together with sustained DC polarization of the the concentration of ACh obtained in the cortical
cortex by a combination of eserine and Ach on the perfusates, in spite of blocking its effect upon cortical
mi
11
5mV.
5sec.
Fig. 1-3. Sustained rhythmic seizure discharge with surface negative DC shifts from isolated undercut cerebral cortex in the cat, after
treatment with a solution of 100 ptg/ml neostigmine and 0.1-0.5% Ach. (Reproduced with permission from Ferguson and Jasper, 1971.)
4
electrical activity. This may be due to the prevention Their convulsions could also be arrested and pre-
of ACh uptake by atropine-blocked receptors, either vented by the administration of pyridoxine.
pre- or postsynaptic. It had been shown by Roberts and Frankel (1950)
that pyridoxine was a cofactor in the production of
Amino acids y-aminobutyric acid (GABA) from glutamic acid by
the enzyme glutamic acid decarboxylase (GAD). This
Following the war, when our research efforts were suggested to us that the Factor I of Florey might well
redirected to peace-time priorities, we began again be GABA. We were frustrated in our search, how-
our search for chemical mechanisms in epilepsy. In ever, by finding that the GABA provided by the
his study of human epileptogenic cortex removed at Merck Company was inactive when tested on the
operation by Dr. Penfield, Dr. Elliott had failed to crustacean stretch receptor bioassay preparation.
show a significant abnormality in oxidative metabo- With the use of a large vat loaned by the Merck
lism when suitable controls were carried out. Since Company, it was possible to process hundreds of
he and his colleague, Dr. Pappius, failed to confirm pounds of beef brain to provide sufficient extract for
the initial results with Tower that there may be a analytical purification. Alan Bazemore was able to
significant abnormality in Ach metabolism in human produce a crystalline extract that contained a high
focal epileptogenic brain tissue, we turned our atten- concentration of the active ingredient of Factor I.
tion to the possibility that there may be a defect in These crystals were then shown by infrared spectro-
inhibitory mechanisms rather than an increase in an scopy and chromatography to be GABA. We never
excitatory chemical transmitter substance. At this did discover what was contained in the sample of
time there was no known inhibitory transmitter sub- presumed GABA that had been supplied by the Merck
stance in cerebral cortex. Company.
We had heard of the work of an Austrian Zoologist The proposal that GABA might be an important
by the name of Ernst Florey, who had extracted from inhibitory neurotransmitter in the brain was then given
mammalian brain a substance that had an inhibitory support by our electrophysiological studies of the
action upon the stretch receptor in the claw of the effects of the local application of GABA to the
crayfish, decreasing or arresting its discharge in re- cortical surface (Iwama and Jasper, 1957; Jasper et
sponse to a constant stretch. He had called it "Factor al., 1958; Jasper, \960a,b) and by Killam (1957,
I" for inhibition. He was then working with Wiersma 1958), and Killam and Bain (1957), who proposed
in California. We invited him to come to Montreal, that seizures caused by convulsant hydrazides (thio-
with his wife and assistant, Elizabeth. semicarbazide) were due to a depletion of GABA by
Elliott was able to purify Florey's extract procedure blocking of the action of pyridoxine, suggesting that
until we were convinced that it would be worthwhile GABA may well be an important inhibitory trans-
to identify the chemical substance that had this re- mitter in the brain. Kuffler and Edwards (1958) then
markable inhibitory action on the crustacean stretch showed that GABA was an inhibitory transmitter that
receptor bioassay preparation. duplicated the action of inhibito1ry nerves in the crus-
To aid in this task, we were able to get the help tacean neuromuscular system.
of an analytical chemist from the Merck Company Making use of the cortical superfusion technique
by the name of Alan Bazemore. We were directed in we had developed for the study of Ach, we were
our search by the report by Hunt et al. (1954) of a then able to show that the liberation of GABA and
patient who had convulsive seizures that were readily glutamate from the cortex was in fact related to states
arrested by the administration of pyridoxine. Malony of sleep and waking in relation to sections of the
and Parmalee (1954) had reported convulsions in brainstem (Fig. 1-4) and in relation to stimulation of
infants due to a pyridoxine-deficient diet, and Coursin
(1954) reported seizures in a number of infants who 'The story of GABA was reviewed by Elliott and Jasper in
were fed a pyridoxine-deficient "baby food" diet. 1959 and summarized in a tribute to Elliott by Jasper in 1984.