NERVE CONDUCTION PATTERNS DETERMINED ELECTRONICALLY
FOR ANALYSING PERIPHERAL NERVES BEHAVIOR IN VIVO
EROS ABRANTES ERHART*; JOSÉ F U R L A N I * * * ; ANTONIO CARLOS BERARDI**; FAUSTO B É R Z I N * * * * ;
WALTER BIAZOTTO****
It has been stated that the nerve impulse is a wave of depolarization
developed in the cell membrane, moving from the CNS to the effectors on
motor nerve fibers, and from the receptors to the CNS on the sensory
fibers. Moreover, it has been experimentally demonstrated that when isolated
nerve cells or fibers are properly stimulated, the depolarization in the
membrane occurs in all directions. Nevertheless, it is accepted that in
normal biological conditions, the peripheral motor and sensory fibers conduct
nerve impulses in one direction only. Or may we consider the antidromic
conduction a normal fact in biology?
The main scope of this paper is not to discuss this problem, but we
have to consider it, since we are trying to establish which are the patterns
of nerve conduction in vivo, based upon electronic data, with the purpose of
subsequent analysis of peripheral nerves behavior in degeneration and
rege-neration processes. We have been working on this matter and on its practical
application in men during the last years (Erhart et at.
3»
4>
5-
6>
7>
s>
9-
1 0) . At
the present, our experiments are being supported by a grant which permitted
us to build the necessary system, which is basically composed of a stimulator,
an electromyograph and a cathode-ray oscilloscope.
MATERIAL, A N D METHODS
D o g s a n e s t h e t i z e d w i t h N e m b u t a l ( A b b o t t ) w e r e operated in order to e x p o s e properly a l l or s o m e of t h e n e r v e s c h o s e n for t h e e x p e r i m e n t in e a c h d o g : n. u l n a r i s
( m i x e d ) , n. h y p o g l o s s u s (chiefly m o t o r ) a n d n. c u t a n e u s brachii m e d i a l i s (chiefly s e n s o r y ) . I n t h e s e e x p e r i m e n t s , 42 n e r v e s of 14 dogs w e r e u s e d .
T h e s u r g i c a l p r o c e d u r e for t h e n e r v e e x p o s i t i o n and t h e care t a k e n to m a i n t a i n e a c h nerve, a s m u c h a s possible, undisturbed in its n a t u r a l c o n n e c t i v e t i s s u e bed, to a v o i d n u t r i t i o n a l d e f i c i e n c i e s w h i c h i n t e r f e r e w i t h the n o r m a l n e r v e b i o l o g y a n d r e g e n e r a t i v e processes, a r e described a n d discussed in s o m e of our f o r m e r papers i n t h e s u b j e c t ( E r h a r t & R e z z e5
, \ 8
) . A f t e r t h e e x p e r i m e n t s , t h e d o g s w e r e killed.
B i p o l a r n i c k e l - c h r o m i u m e l e c t r o d e s w i t h 0 . 5 m m d i a m e t e r , m o u n t e d in p l a s t i c s u p p o r t s a n d circa 1 m m a p a r t one f r o m t h e o t h e r w e r e u s e d . T h e y w e r e c o m m a n d e d by a c h a r r i o t s y s t e m in order t o p e r m i t d e l i c a t e and s m a l l d i s p l a c e m e n t s a n d g o o d c o n t a c t s a l o n g t h e n e r v e t r u n k s . T h e c o n n e c t i o n s b e t w e e n e l e c t r o d e s a n d s t i m u l a t o r or recording s y s t e m w e r e a c h i e v e d by m e a n s of a s e l e c t i v e s w i t c h - b o x s i m i l a r to t h e o n e r e c o m m e n d e d by F o x & K e n m o r e " . A l l the e x p e r i m e n t s w e r e performed in a F a r a d a y c a g e .
I n p r e l i m i n a r y t e s t s for control a n d in order to c a l i b r a t e our e l e c t r o n i c s y s t e m properly, w e h a v e w o r k e d w i t h n e u r o p h y s i o l o g i c a l p r e p a r a t i o n s of i s o l a t e d n e r v e s : frog s c i a t i c and d o g u l n a r and h y p o g l o s s a l n e r v e s . We could observe, a s it w a s e x p e c t e d in s u c h s t a n d a r d n e u r o p h y s i o l o g i c a l p r e p a r a t i o n s , t h a t n e r v e i m p u l s e s f l o w from A to B or f r o m B t o A, Indifferently, d e p e n d i n g o n l y on t h e s t i m u l a t i o n and recording p o i n t s ( F i g . 1 ) . In t h e s e p r e p a r a t i o n s , t h e w h o l e c o m p o u n d t r a c i n g of f a s t and s l o w fibers w a s o b v i o u s l y o b s e r v e d . L o c a l a n e s t h e s i a , x y l o c a i n e 2 % , blocked t h e n e r v e i m p u l s e .
W i t h t h e s e p a t t e r n s e s t a b l i s h e d , t h e proposed e x p e r i m e n t a l s e r i e s w e r e i n i t i a t e d . E a c h n e r v e t r u n k w a s s u r g i c a l l y e x p o s e d ( 4 - 5 c m ) b u t m a i n t a i n e d undisturbed, as m u c h a s possible, on its n a t u r a l c o n n e c t i v e t i s s u e bed. I n all t h e e x p e r i m e n t s e q u i v a l e n t s e g m e n t s of t h e n e r v e t r u n k s w e r e u s e d . W e h a v e c h o s e n s h o r t s e g m e n t s f r o m w h i c h n o b r a n c h e s spread off. E l e c t r o d e s A and B, a p a r t from e a c h other circa 2 c m w e r e c a r e f u l l y positioned a s in F i g . 1 . Then, t h e n e r v e t r u n k w a s s t i m u l a t e d w i t h b o t h p o s i t i v e a n d n e g a t i v e p u l s e s w i t h 50 /tsec of d u r a t i o n , 0 . 8 pyclesi/sec of frequency, w i t h a n a m p l i t u d e from zero to t h r e s h o l d i n t e n s i t y and t h e n up t o s u p r a t h r e s h o l d l e v e l , 6 to 8 Volts, in order t o o b t a i n d e p o l a r i z a t i o n of all t h e fibers w h i c h , in t h e n e r v e s e g m e n t u n d e r study, w e r e c o n d u c t i n g from A t o B and f r o m B t o A . S t i m u l a t i o n w a s i n d i f f e r e n t l y applied e i t h e r in t h e p r o x i m a l ( A ) or d i s t a l ( B ) electrode, and t h e n i n v e r t e d by m e a n s of t h e s e l e c t i v e s w i t c h - b o x of t h e s t i m u l a t o r .
R E S U L T S
T h e n e r v e s studied under t h e in vivo e x p e r i m e n t a l c o n d i t i o n s previously d e s -cribed s h o w e d t h e f o l l o w i n g :
b — T h e 16 h y p o g l o s s a l n e r v e s p r e s e n t e d t y p i c a l a c t i o n p o t e n t i a l in t h e pro-x i m a l - d i s t a l c o n d u c t i o n ( F i g . 2 I I I ) . In t h e s e m o t o r n e r v e s , m a i n t a i n e d undisturbed in their c o n n e c t i v e t i s s u e bed, t h e recorded a c t i o n p o t e n t i a l of t h e d i s t a l - p r o x i m a l c o n d u c t i o n w a s a l w a y s s m a l l e r in a m p l i t u d e ( F i g . 2 I V ) , e v e n w h e n s l i g h t s u p r a -threshold a n d h i g h e r f r e q u e n c i e s s t i m u l a t i o n s w e r e used, or w h e n t h e position of t h e e l e c t r o d e s w e r e c h a n g e d a l o n g t h e n e r v e t r u n k . W e m a y suppose t h a t t h e proprioceptive fibers of t h e h y p o g l o s s a l n e r v e a r e responsible for t h i s d i s t a l p r o -x i m a l c o n d u c t i o n .
c — In t h e 7 m e d i a l brachial c u t a n e o u s n e r v e s , chiefly sensory, it w a s o b s e r v e d t h a t its a c t i o n p o t e n t i a l w a s t y p i c a l in t h e d i s t a l - p r o x i m a l c o n d u c t i o n ( F i g . 2 VI) and had s m a l l e r a m p l i t u d e in t h e p r o x i m a l - d i s t a l c o n d u c t i o n ( F i g . 2 V ) . I n t h e s e l a t t e r n e r v e s w e m a y suppose t h a t t h e p o s t - g a n g l i o n i c s y m p a t h e t i c n e r v e fibers a r e responsible for t h e p r o x i m a l - d i s t a l c o n d u c t i o n .
d — All t h e n e r v e s — ulnar, h y p o g l o s s a l and m e d i a l brachial c u t a n e o u s — w h i c h a f t e r b e i n g w o r k e d on in vivo, w e r e i s o l a t e d f r o m t h e i r n a t u r a l c o n n e c t i v e beds, t r a n s s e c t e d and suspended on t h e e l e c t r o d e s , a s is n o r m a l l y done in n e u r o -p h y s i o l o g i c a l -pre-parations, -presented, in a c c o r d a n c e w i t h t h e l i t e r a t u r e , ty-pical a c t i o n p o t e n t i a l s in b o t h d i r e c t i o n s : p r o x i m a l - d i s t a l a n d d i s t a l - p r o x i m a l ( F i g . 2 VII and V I I I ) .
T h e a n o m a l o u s records w h i c h w e r e o b t a i n e d from six n e r v e s ( o n e ulnar, t h r e e h y p o g l o s s a l and t w o m e d i a l brachial c u t a n e o u s ) s e v e r e l y injured by s u r g i c a l m a n i -p u l a t i o n , distension, e x c e s s b l e e d i n g or i s c h e m i a , w e r e o b v i o u s l y not considered in t h e s e d a t a .
D I S C U S S I O N
In general our results, regarding the compound waves, latency, amplitude,
etc., are in accord with the literature; but, as they presented the above
mentioned particularities, they must be further discussed.
When a nerve maintained in its natural connective tissue bed is
sti-mulated, the neighbouring tissues, including muscle fibers, integrate with
the compound waves which appear on the scope screen. For that reason,
our system included an oscilloscope to record fast events, that is, the action
potentials of nerve fibers, and an electromyograph, for slow events recording,
such as action potentials in muscle fibers groups.
As the behavior of nerves in vivo involves biochemical and metabolic
processes, the surgical procedure and the electrodes positioning were such
as to maintain the nerve fibers undisturbed, as much as possible, in their
natural connective tissue bed. Being so, in our preparations we had a
shunt-ing effect which was partially diminished by groundshunt-ing (Fig. 1 ) . We
con-sidered it as a constant when stimulating and recording from A to B and
from B to A because: i — if the shunting effect had really interfered in
our results, we could not obtain, as we did, constancy in the recorded action
potentials of the 13 ulnar, 16 hypoglossal and 7 medial brachial cutaneous
nerve trunks studied, ii — the nerve trunk segment used was always a
short one, circa 2 cm long, distance between electrodes A and B. iii —
from these nerve trunk segments no branches spread off.
compared to those obtained by the experimental methods generally used in
the stimulation of nerves, which constitute always an attack to nerve cell
and nerve fiber integrity (
1.
12>
1 3»
1 5>
1 6) . The anesthesia of the animal, by
itself, will certainly interfere too on different structures, including the
sy-naptic mechanisms. The abnormal, continuous stimulation, in high frequencies,
will probably interfere also with what is considered normal nerve cell or
fiber behavior. For that reason we used in our experiments in vivo, threshold
stimulation, short duration pulses and low frequencies, to allow metabolic
reestablishment of the nerve fibers being studied, as well as reposition of
possible electric disturbances in the nerve trunk environment.
The results we have obtained on dog ulnar, hypoglossal and medial
brachial cutaneous nerves, indicating a specific unidirectional conduction on
peripheral motor and sensory fibers, although being quite different from
what has ever been published on the subject up to now, seem to be supported
by neurophysiological, neuroembriological and neuropathological data. Llinás
and colaborators
1 3, as far as we know were the first to speak about
"unidi-rectional preference". They stated: "dendritic action potentials in alligator
Purkinje cells tend to have an unidirectional preference" and "probably many
other nerve cells may have to be considered as highly complex units able
to attain a vast number of dynamic states which would lead to the
gene-ration of a large variety of functional patterns". They talk about dendrites
but, if it is accepted that the nerve impulses enter through he dendrites
and leave the cell body through the axon, in these latter there must be too
an unidirectional preference. Our tracings in peripheral nerves, in vivo
con-ditions, showed this fact. Weiss & E d d s
1 8concluded that sensory nerves
form no functional synapses with muscles; and Robbins
1 7wrote: "if the
functional potential of a sensory nerve is not the key to the origin of sensory
specificity, other specifying mechanisms must be invoked to explain nerve
growth to a specific location". We do agree with these authors. There
must be something specific in the nerve cell body whose nature we do not
know, that makes motor and sensory nerve fibers in vivo behave differently
one from another. If Mother Nature has build these two systems (motor
and sensory) embriologically, morphologically and functionally different one
from another, Men will state that in vivo motor and sensory peripheral nerve
fibers have no specific conduction! Polio lesions are chiefly related to motor
neurons and those of tabes dorsalis, to sensory neurons. Moreover, nerve
lesions are distinguishable one from another by the condition of motor,
sen-sory and sympathetic functions, as revealed by clinical examination. These
facts permit us to conclude that there must be something biochemical,
metabolic or something else, concerning nerve-fiber structure in relation to
nerve-fiber function to be investigated.
S U M M A R Y
be in accordance with those described in the literature. However, our
tra-cings showed a new additional fact, i . e . , t h a t motor and sensory peripheral
nerve fibers have a specific unidirectional conduction (centrifugally for motor
and centripetally for sensory), as long as these nerves were maintained
undis-turbed in their natural connective tissue bed. Although these facts
corres-pond to what is considered normal biological behavior of nerve fibers, when
in their natural environment, as far as we know, this has not been
demons-t r a demons-t e d before in neurophysiological experimendemons-ts.
R E S U M O
Padrões de condução de impulsos nervosos, determinados eletronicamente,
para análise de comportamento de nervos "in vivo"
Padrões de condução de impulsos nervosos foram determinados
eletrô-nicamente, in vivo, nos nervos ulnar (13), hipoglosso (16) e cutâneo medial
do braço (7) de cães anestesiados. Os traçados obtidos confirmaram, em
linhas gerais, os descritos na literatura. Todavia, demonstraram um fato
novo, adicional, isto é, que fibras motoras e sensitivas, integrantes de nervos
periféricos, apresentam uma condução específica, unidirecional (centrífuga
nas fibras motoras e centrípeta nas sensitivas), desde que mantidas
pratica-m e n t e intactas epratica-m seus respectivos leitos conectivos naturais. Epratica-mbora este
tipo de condução específica corresponda ao que se admite e aceita como
com-portamento normal, biológico, dessas fibras nervosas, e constitua ainda, base
do exame neurológico, esta evidência nunca foi demonstrada anteriormente
e m experiências e preparações neurofisiológicas.
R E F E R E N C E S
1 . B O W M A N , J . & COMBS, C . M . — D i s c h a r g e p a t t e r n s of l i n g u a l s p i n d l e a f f e r e n t f i b e r s in t h e h y p o g l o s s a l n e r v e of t h e R h e s u s m o n k e y . E x p t l . N e u r o l . 2 1 : 1 0 5 , 1 9 6 8 .
2 . B U R G E S S , P . R . & P E R L , E . R . — M y e l i n a t e d a f f e r e n t f i b e r s r e s p o n d i n g s p e c i f i c a l l y t o n o x i o u s s t i m u l a t i o n of t h e s k i n . J . P h y s i o l . ( L o n d o n ) 1 9 0 : 5 4 1 , 1 9 6 7 .
3 . E R H A R T , E . A . — N o r m a l n e r v e f i b r e s in t h e d i s t a l s e g m e n t of n e r v e s c o m -p l e t e l y s e -p a r a t e d f r o m t h e -p r o x i m a l s t u m -p f o r m o r e t h a n six m o n t h s . A r q . N e u r o - P s i q u i a t . ( S ã o P a u l o ) 2 0 : 2 8 9 , 1 9 6 2 .
4 . E R H A R T , E . A . & E R H A R T , M . B . — N o r m a l a x i s - c y l i n d e r s in t h e d i s t a l s e g m e n t of n e r v e s c o m p l e t e l y s e p a r a t e d f r o m t h e p r o x i m a l s t u m p f o r u p t o 24 y e a r s . A n a t . R e c . 136:189, 1 9 6 0 .
5 . E R H A R T , E . A . & R E Z Z E , C . J . — N e r v e f i b r e s in i s o l a t e d s e g m e n t s of d o g u l n a r n e r v e a f t e r c o m p l e t e b r a c h i a l p l e x o t o m y a n d p e r i a x i l a r a r t e r y s y m p a -t h e c -t o m y . A r q . N e u r o - P s i q u i a -t . ( S ã o P a u l o ) 2 3 : 8 2 , 1 9 6 5 .
7 . E R H A R T , E . A . & R E Z Z E , C . J . — E x p e r i m e n t a l d a t a a n d p r a c t i c a l r e s u l t s w h i c h m o d i f y t h e p r e s e n t c o n c e p t s of p e r i p h e r a l n e r v e f i b r e s d e g e n e r a t i o n a n d r e g e n e r a t i o n . P r o c . V I n t e r n a t . C o n g r e s s of N e u r o p a t h o l . ( Z u r i c h ) p . 864-867, 1 9 6 5 . P u b l i s h e d by E x c e r p t a M e d i c a .
8 . E R H A R T , E . A . & R E Z Z E , C . J . — E f f e c t of e x p e r i m e n t a l d e v a s c u l a r i z a t i o n o n p e r i p h e r a l n e r v e s . A r q . N e u r o - P s i q u i a t . ( S ã o P a u l o ) 2 4 : 7 , 1 9 6 6 .
9 . E R H A R T , E . A . & R E Z Z E , C . J . — F u r t h e r d i s c u s s i o n o n t h e n e w g r o i n g n e r v e f i b r e s w h i c h r e p o p u l a t e t h e d i s t a l s e g m e n t of n e r v e s c o m p l e t e l y s e p a r a t e d f r o m t h e p r o x i m a l s t u m p f o r m o r e t h a n s i x m o n t h s . A r q . N e u r o - P s i q u i a t .
( S ã o P a u l o ) 2 4 : 9 1 , 1 9 6 6 .
1 0 . E R H A R T , E . A . ; R E Z Z E , C . J . & B I A Z O T T O , W . — T h e e c t o p i c n e w l y - f o r m e d n e r v e f i b r e s w h i c h r e p o p u l a t e t h e l o n g - t i m e d e n e r v a t e d a n d a t r o p h i c c h i c k s k e l e t a l m u s c l e . A r q . N e u r o - P s i q u i a t . ( S ã o P a u l o ) 2 6 : 1 8 7 , 1 9 6 8 .
1 1 . F O X , L . J . & K E N M O R E , P . — T h e e f f e c t of i s c h e m i a o n n e r v e c o n d u c t i o n . E x p t l . N e u r o l . 1 7 : 4 0 3 , 1 9 6 7 .
1 2 . L A N D A U , M . L . ; C L A R E , M . H . & B I S H O P , G . H . — R e c o n s t r u c t i o n of m y e l i n a t e d n e r v e t r a c t a c t i o n p o t e n t i a l s : a n a r i t h m e t i c m e t h o d . E x p t l . N e u r o l . 22:480, 1 9 6 8 .
1 3 . L L I N Á S , R . ; N I C H O L S O N , C . & P R E C H T , W . — P r e f e r r e d c e n t r i p e t a l c o n -d u c t i o n of -d e n -d r i t i c s p i k e s in a l l i g a t o r P u r k i n j e c e l l s . S c i e n c e , 163:184, 1 9 6 9 .
1 4 . MC L E O D , J . G . & W R A Y , S . H . — C o n d u c t i o n v e l o c i t y a n d f i b r e d i a m e t e r of t h e m e d i a n a n d u l n a r n e r v e s of t h e b a b o o n . J . N e u r o l . N e u r o s u r g . P s y c h i a t . 30:240, 1 9 6 7 .
1 5 . M O R I M O T O , T . ; T A K A T A , M . & K A W A M U R A , Y . — E f f e c t of l i n g u a l n e r v e s t i m u l a t i o n o n h y p o g l o s s u s m o t o n e u r o n s . E x p t l . N e u r o l . 2 2 : 1 7 4 , 1 9 6 8 .
1 6 . P A I N T A L , A . S . — A c o m p a r i s o n of t h e n e r v e i m p u l s e of m a m m a l i a n n o n ¬ m e d u l l a t e d n e r v e f i b e r s w i t h t h o s e of t h e s m a l l e s t d i a m e t e r m e d u l l a t e d f i b e r s . J . P h y s i o l . ( L o n d o n ) 1 9 3 : 5 2 3 , 1 9 6 7 .
1 7 . R O B B I N S , N . — P e r i p h e r a l m o d i f i c a t i o n of s e n s o r y n e r v e r e s p o n s e s a f t e r c r o s s -r e g e n e -r a t i o n . J . P h y s i o l . ( L o n d o n ) 1 9 2 : 4 9 3 , 1 9 6 7 .
1 8 . W E I S S , P . & E D D S , M . V . J r . — S e n s o r y - m o t o r n e r v e c r o s s e s in t h e r a t . J. N e u r o p h y s i o l . 8 : 1 7 3 , 1 9 4 5 .
