1953_Bradley_39_1.pdf

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SOOIETY,
A. F. ZAYAT.
Department
16-17
JANUARY
1953
l3P
Sodium chloride and cardiac muscle.
of Physiology,
By
R. J.
S. McDoWALL and
King's Oollege, London
The rat
ventricle
preparation in Krebs's
solution
is convenient for the
study
of mammaliam
cardiac
muscle (McDowall
&
Zayat, 1952), but
shows some
unusual features.
If stimulated rhythmically, it is found that the
strength
of its
contractions
is a function of the frequency of stimulation. Thus if stimulated
at
40 per min,
contraction height is only half that of stimulation at 4 per min, which produces
a maximum response. A short rest from more rapid rates causes a temporary
recovery of the response. The diminution
of the response with increased
frequencies occurs whether a square wave
stimulus
or a simple break shock is
used.
If, however, the sodium chloride in the bath is reduced from 0·69 to 0·38
%,
osmotic pressure being maintained by
sucrose,
the reduced contraction height
with increased frequencies is very much less,
and
may be
absent altogether
unless high frequencies are used.
As
the condition
of
the
muscle becomes
poorer, the influence
of
increased frequency
becomes
more
apparent. The
change with low
sodium
does not
appear to
be
due
to any
change
in the
con-
ductivity
of
the
solution
affecting the
strength of the stimulus,
for the
prepara-
tion exhibits
the all-or-none
phenomenon
and
is not affected by changes in the
strength of stimulus above
the minimum
necessary
to produce
contraction.
The results appear to
suggest that when
the
muscle
is active
it
takes up
sodium
chloride
like nerve but gets rid
of
it relatively
slowly
and therefore
cannot
contract
maximally unless the
sodium
extrusion is made easier by
reduction of the sodium
chloride
in the
bath.
REFERENCE
McDowall, R. J. S.
&
Zayat, A. F. (1952).
J.
Physiol.
117,
75P.
The effect of amphetamine
and n-Iysergic acid diethylamide
(LSD 25) on the electrical activity of the brain of the conscious
cat.
By
P.
B. BRADLEY and
J.
ELKES.
Department of Experimental
Psyohiatry,
Medioal School, Birmingham
15
The
effect
of DL-amphetamine, its D-
and
L-isomers,
and
of D-lysergic acid
diethylamide
(Stoll, 1947) on the
electrical
activity of the brain has been
studied
in the
conscious
unrestrained
animal, and
in acute experiment.
Large
doses of DL-amphetamine (3-5 mglkg
by
mouth)
produced
rhythms not unlike
those
seen
in the normal alert animal, i.e. low
amplitude,
diffuse, fast (15-30
cis)
activity in
all
regions. There was also
a corresponding
change in behaviour,
the animal becoming more attentive,
and,
in
some
instances,
excited.
The
cortical response to rhythmic photic
stimulation,
recorded over
the visual
--------------.-----------
14P
PROOEEDINGS
OF
THE
PHYSIOLOGIOAL
area, was
increased in amplitude
at all
frequencies
between
2
and 25
per
sec.
The effects
of
D-lysergic acid diethylamide
(15~25
fLg/kg by mouth) on
electrical
activity
and behaviour
were similar
to those of DL-amphetamine,
but no change in the response
to
photic
stimulation could
be observed
with this drug. The effects of barbiturate anaesthesia (pentobarbitone
30 mg/kg) on the electrical
activity
of the brain remained unaffected by
amphetamine when recorded
at
the
cortical
level. There was, however, some
increase in the response to photic
stimulation
at the level of the lateral
geniculate body. Large doses of D-lysergicacid diethylamide (50~100fLg/kg)
completely abolished the electrical
activity
characteristic of moderate barbi-
turate
anaesthesia,though
leaving the depth of anaesthesia
apparently
unaffected.
The
characteristic
waxing and waning activity seen in the
corticogram
of
the brain
sectioned
in
situ
at the level of the Ist cervicalvertebra (Bremer, 1938)
was
abolished by intravenous amphetamine in doses of 1·5~3 mg/kg. This
activity was restored by
section at
midbrain level in the
same
preparation,
and remained unaffected by further injections of
amphetamine. D-Lysergic
acid diethylamide in doses of up
to
100fLg/kghad no
effect
on the
electrical
activity
of
either
of these acute preparations.
The
effects
of amphetamine
and
D-lysergic acid diethylamide on
the
corticogram thus differ from
atropine,
L-hyoscyamine and
physostigmine
in
their dependence upon mesencephalic or
spinal connexions. Again, there
is
better
correlation
between electrical activity and behaviour in the
case
of
amphetamine and
D-lysergic
acid
diethylamide than there is
with atropine,
L-hyoscyamine and physostigmine. Amphetamine may
act
on
receptors:
The differences between the
effects
of D-lysergic
acid
diethylamide and
amphetamine, outweigh any
common
features shared by these two drugs, and
point to probable differencesin their
mode
of action.
REFERENCES
Bremer, F. (1938).
L'activitt
electriquede
l'ecorce cerebrale.
Paris:
Hermanri
Magoun,
H. W. (1952).
Res. P~lbl.
Ass.
Nerv. Ment.Dis.
30, 480.
Stoll,
W. A. (1947).
Schweiz. Arch.
Neurol.
Psychiat.
60, 279.
The
effect of atropine, hyoscyamine, physostigmine
and
neostigmine on the electrical activity of the brain of the
conscious cat.
By P. B.
BRADLEY
and
J. ELKES.
Department of
Experimental Psychiatry, Medical
School,
Birminqhan;
15
Electrical
activity
from the lateral,
sigmoid,
ectosylvian
and suprasylvian
gyri and the
caudate, medial
and
lateral
thalamic
and posterior hypothalamic
nuclei has been recorded in the
consciousunrestrained cat,
using
an
implanted

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