Specific and high concentrations of acetyl-
cholinesterase are seen in both retina and superior
colliculus using histochemical staining technique.”
Microiontophoretic and more conventional neuro-
pharmacological experiments have established
that cholinergic receptors do exist in these
areas.?*741_ Furthermore, some of these experi-
ments indicate that certain of the cholinergic
receptors are nicotinic and are not blocked by
atropine.2**_ The duration of the apparent blind-
ness extends to 1.0-2.0 hours after mevinphos
injection. This is the approximate duration of
the behavioral and electrophysiological changes
seen after mevinphos but is rather less than the
duration of atropine effects, judged by pupillary
reactivity and diameter. This suggests that the

blindness is related to the combined actions of
atropine and mevinphos, and could result from
the presence of high levels of acetylcholine at
unblocked nicotinic receptors at a time when the

atropine-sensitive muscarinic receptors are
blocked.

Vv. Summary.

Three squirrel monkeys did not respond to
visual stimuli for at least one hour following
combined administration of mevinphos (Phos-
drin) and atropine. Therefore, aerial applicator
personnel being tested for mevinphos (Phosdrin)
poisoning with atropine may. show potentially
hazardous dysfunctions of visual perception.
Some mechanisms for this effect were discussed.

REFERENCES

1, Abood, L. G., Ostfeld, A., and Biel, J. H.: Structure-
Activity Relationships of 3-Piperidyl Benzilates with
Psychotogenic Properties, ARCH. INT. PHARMA-
CODYN, 120:186-197, 1959.

. Bradley, P. B. and Wolstencroft, J. N.: Actions of
Drugs on Single Neurones in the Brain Stem, BRIT.
MED, BULL, 21:15-18, 1965.

3. Curtis, D. R. and Crawford, J. M.: Central Synaptic
Transmission-Microelectrophoretic Studies, ANN.
REV. PHARMACOL., 9:209-240, 1969.

4. Durham, W. F.: Effects of Pesticides on Man, in
C.O. Chichester, ed. Research in Pesticides, Academic
Press, New York, 1965,

5. Hayes, W. J.: Pesticides and Human Toxicity, ANN.
N.Y. ACAD. SCL, 160 :40-54, 1969.

6, Health, D. F.
New York, 1961.

~p

irganophosphorus Poisons, Pergamon,

7, Krnjevic, K.: Central Cholinergic Pathways, FED.
PROC., 28(1) :113-120, 1969.

8, Manocha, 8. L. and Shantha, T. R.: Macaca Mullatta-

Enayme Histochemistry of the Nervous System, Aca-

demic Press, New York, 1970.

Metcalf, D. R, and Holmes, J. H.: EEG, Psycho-

logical and Neurological Alterations in Humans with

Organophosphorus Exposure, ANN. N. Y. ACAD.

SCL, 160 :357-365, 1969.

10, Natoff, I. L. Organophosphorus Pesticides: Phar-
macology, PROG. MED. CHEM., 8:1-87, 1971.

11, Phyllis, J. W.: The Pharmacology of Thalamic and
Geniculate Neurones, INT. REV, NEUROBIOL,
14:1-48, 1971.

12. Russell, R. W.: Behavioral Aspects of Cholinergic
‘Transmission, FED. PROC., 28(1) :121-181, 1969,

18. Weiss, B. and Laties, V. G.: Behavioral Pharma-
cology and Toxicology, ANN. REV. PHARMACOL.,
9:297-826, 1969.

2

20313



REFERENCES

1. Adey, W. R.: Recent Studies of the Rhinencephalon
in Relation to Temporal Love Epilepsy and Be-
havioral Disorders, INT. REV. NEUROBIOL,
1:1-48, 1959.

2, Anderson, P. and Lomo, T.: Mode of Control of

Hippocampal Pyramidal Discharges. In: The Neural

Control of Behavior, edited by R. Whalen and RB.

Thompson, New York, Academic Press, 1970.

Auerbach, A. A.: Transmitter Release at Chemical

Synapses. In: Structure and Function of Synapses,

G. D. Pappas and D. P. Purpura, editors, Raven,

New York, 1972.

. Biscoe, T. J., and Straughn, D. W.: Micro-Blectro-
phoretic Studies of Neurones in the Cat Hippo-
campus, J. PHYSIOL, 183:341-359, 1966.

5. Blackstad, T. W.: On the Termination of Some
Afferents to the Hippocampus and Fascia Dentata,
ACTA ANAT,, 16:202-214, 1958.

. Blakemore, C., Iversen, S. D., and Zangwill, O. L.:
Brain Functions, ANN. REV. PSYCH., 23:413-456,
1972.

7. Fink, Max: EEG and Human Psychopharmacology,

ANN, REV. PHARMACOL, 9:241-258, 1969.

Friede, R. L.: Topographic Brain Chemistry, Aca-

demic Press, New York, Chapter X :237-281, 1966.

9. Green, J. D.: The Hippocampus, PHYSIOL. REV.,
44 :561-608, 1964.

10. Hayes, Wayland J.: Pesticides and Human ‘Toxicity,
ANN. N. Y. ACAD. SCI., 160:40-54, 1969.

11. Heath, D. F.:Organophosphorus Poisons, Pergamon
Press, New York, 1961.

12. Izquierdo, I. and Izquierdo, J. A.: Effects of Drugs
on Deep Brain Centers, ANN, REV. PHARMACOL,
11 :189-208, 1971.

13, Koelle, George B.: Significance of Acetylcholinest-
erase in Central Synaptic Transmission, FED.
PROC., 28(1) :95-100, 1969.

tad

~

2

@

14, Lewis, Mark F., Mertens, Henry W., and Steen, Jo
Ann: Behavioral Changes from Chronic Exposure
to Pesticides Used in Aerial Application: Effects of
Phosdrin on the Performance of Monkeys and
Pigeons on Variable Interval Reinforcement Sched-
ules. FAA Office of Aviation Medicine Report No.
AM-72-29, 1972.

15. Lewis, P. R. and Shute, C. C. D.: The Cholinergic
Limbie Syste Projections to Hippocampal Forma-
tion, Medial Cortex, Nuclei of the Ascending Cholin-
ergic Reticular System, and the Sub-fornical Organ
and Supra-optic Crest, BRAIN, 90:521-540, 1967.

16. McLardy, T.: Hippocampal Formation as Detector

Coder of Temporal Patterns, PERSPECTIVES
BIOL. MED. 443-452, 1959.
17. Manocha, Sohan L., and Shantha, Totada R.:

Macaca Mulatta, Enzyme Histochemistry of the
Nervous System, Academic Press, New York, 1970.

18. Metcalf, D. R., and Holmes, J. H.: EEG, Psycho-
logical and Neurological Alterations in Humans with
Organophosphorus Exposure, ANN. N. ¥. ACAD.
SCI, 160 :357-365, 1969.

19. Namba, T., Greenfield, M., and Grob, D.: Malathion
Poisoning, ARCH. ENVIRON. HEALTH, 21 :533-541,
1970.

20. Natoff, I, L.: Organophosphorus Pesticides: Pharma-
cology, PROGR. MED. CHEM., 8:1-37, 1971.

21. Pradhan, S. N., and Dutta, S$. N.: Central Cholin-
ergic Mechanisms and Behavior, INT. REV. NEURO-
BIOL., 14 :173-231, 1971.

22. Segal, M., and Olds, J.: Behavior of Units in Hippo-
campal Circuit of the Rat during Learning, J.
NEUROPHYSIOL, 35 :680-690, 1972.

28. Stumpf, (.: Drug Action on the Electrical Activit:
of the Hippocampus, INT. REV. NEUROBIOL.,
8 :77-138, 1965.

24, Werman, R.: CNS Cellular Level: Membranes, ANN.
REV. PHYSIOL., 34 :837-374, 1972.

2804


usual squealing and aggressive behavior directed
toward the hand or hands holding them. If
touched, they would jump away from the touch
and, sometimes, bare their teeth and/or squeal.
Responses to sound were clearly normal. A
sudden noise, such as tapping the cage side or
key jingling, caused a startle response followed
immediately by orientation toward the sound.
The animals also followed movements of
“strange” noises, such as key jingling, in the
space around them. All of these responses to
auditory stimuli were quite normal for a squirrel
monkey.

However, to our complete surprise, the ani-
mals which exhibited such normal responses to
other stimuli appeared to be totally blind. There
was no response of any kind to moving spots of
light or sudden flashes which would normally
elicit startle or orientation movements. There
was also no response at all to “threatening”
movements toward the animal which normally
elicited startle, orientation, retreat and teeth-
baring responses. Further, if a flashlight beam
was directed into the animals’ eyes, which were
partly dilated from the atropine, there was no
movement or any indication that the animal was
being stimulated in any way. Normally, the
responses to this stimulus include instant eyelid
closure, head turning and escape movements.
Varying ambient light from 50 ft.candles to
0.1 ft.-candles (bright to dim room light) had
no effect on this lack of response. However, at
times the animals gave the observers the im-
pression that they realized that something was
happening when lights were flashing, etc., but
they did not know specifically what it was. This
period of blindness lasted for 1.5-£0.5 hours.
Some vague signs of visual sensitivity were seen
after this time followed within 5-10 minutes by
complete visual normality—normality within the
limits of these admittedly relatively crude ob-
servations. The animals remained slightly weak
and “looked ill” for a further 2-8 hours, and all
were completely normal the next morning—20
hours after injection.

IV. Discussion.

These results indicate a very serious potential
hazard to aerial applicator personnel. In cases
of exposure to both atropine and mevinphos
some degree of centrally mediated impairment
of visual function is probably to be expected.

Blindness, seen here, is very dramatic and cer-
tainly has not been reported from the field.‘ * ¢ 9 *«
However, it seems likely from these preliminary
experiments that combinations of mevinphos and
its nominal antagonist atropine could cause some
degree of potentially dangerous visual dysfunc.
tion in aerial applicator personnel.

These effects are unique. There are no reports
in the literature of blindness following OP o1
atropine poisoning in experimental animals o1
man. High doses of atropine alone, in excess 0:
10 mg/kg, will cause a complex variety of be
havioral disorders and bizarre behavior pattern:
in cats, monkeys and man, ”*** but the animal:
under study appeared reasonably normal, excep
for their blindness. OP poisoning can, of course
lead to visual dysfunction of peripheral origin,‘ *
but centrally-mediated visual deficit has not beer
reported in any studies available to us. Th
animals did go into seizures after mevinphos
and the blindness could possibly be a post-icta
phenomenon. However, the rapid recovery o
normal tactile and auditory responses tends t:
argue against this.

Perhaps the most surprising symptom seen wa
the complete lack of response to a bright flash
light beam shone directly into the animal’s eye
in a darkened room. This stimulus was painfu
to the human observers and normally elicite:
rapid escape behavior in the monkeys. Agair
other sensory responses seemed normal. Indeec
the animals would respond to the “click” mad
by the switch on the flashlight some four fee
away. The lack of any response to the brigh
light into the eyes argues that the blindness i
real (not due, say, to inattention) and that th
locus of action for this effect must be in th
retina or the superior colliculus. In either cas
oculomotor reflexes would tend to be inhibitec
which would not be true for a block in the laters
geniculate nucleus or visual cortex. Howeve:
the monkeys at times seemed to know that some
thing was happening during periods of visut
response testing and this is inconsistent with tk
notion of a complete retinal blockade. Thus, tk
primary localization of the blindness-producin
OP-+atropine effect seems most likely to be i
superior colliculus. The blindness seen is, hov
ever, more severe than that produced by massiy
ecollicular lesions so the collicular effects cann
be the only factors.




TECHNICAL REPORT STANDARD TITLE PAGE

T Report No. %. Government Accession No.

FAA~AM- 73-4

3. Recipient's Catalog No.

. Title and Subtitle

TRANSIENT BLINDNESS DUE TO THE COMBINED EFFECTS
OF MEVINPHOS AND ATROPINE

5. Report Date
February 1973

&. Performing Organization Code

Author(s)

Revzin, Alvin M., Ph.D.

8. Performing Organization Report No.

> Performing Organization Name and Address

FAA Civil Aeromedical Institute
P, 0. Box 25082

Oklahoma City, Oklahoma 73125

(0. Work Unit No.

11. Contract or Grant No.

1 Sponsoring Agency Name and Addres=
dffice of Aviation Medicine
Federal Aviation Administration
800 Independence Avenue, S.W.
qashington, D.C, 20591

- Type of Report and Period Covered

QAM Report

14. Sponsoring Agency Code

+ Supplementary Notes

Chis work was performed under Task No, AM-B-73-TOX~-15,.

> Abstract

three squirrel monkeys did not respond to visual stimuli for at least one hour
following combined administration of mevinphos (Phosdrin) and atropine,
therefore, aerial applicator personnel being treated for mevinphos (Phosdrin)
soisoning with atropine may show potentially hazardous dysfunctions of visual
verception, Some mechanisms for this effect were discussed,

Key Words 18, Distribution Stotement

esticides Availability is unlimited. Document may
xganophosphates be released to the National Technical
tropine Information Service, Springfield,
lindness Virginia 22151, for sale to the public.
onkeys

Security Classif. (of this report) 2D. Security Classif, (of this page) DI. No. of Pages | 22. Price
Unclassified Unclassified 3 $3.00

‘m DOT F 1700.7 (8-69)



of a causal relationship between the changes in
hippocampal potentials seen here and their be-
havioral inhibition. As in the present study, no
peripheral symptomatology was seen at doses of
less than 0.250 mg/kg.

Perhaps the most noteworthy finding was that
mevinphos could induce hippocampal biopoten-
tial and behavior changes—including seizure
activity—without any of the usual peripheral
manifestations of OP poisoning. This is a bit
surprising, and disquieting. Although mevin-
phos is said to penetrate the blood-brain barrier
more readily than most other OP pesticides, it
does not penetrate freely." 2° Thus, one would
expect that peripheral effects would tend to de-
velop before the CNS effects of the OP. That
this order is reversed suggests that the effects of
mevinphos on AChE in the CNS differ from
those in the periphery and/or that mevinphos
has actions in the CNS not directly related to its
effects on AChE.

More importantly, the data suggest that aerial
applicator personnel exposed to mevinphos—and,
perhaps, the other OPs—can suffer significant
CNS dysfunctions, even local hippocampal seiz-
ures, in the absence of the usual “peripheral”
pathognomonic signs. Since hippocampus “plays
a crucial role in the programming of acquired
sensory-response patterns,”® the hazards to the
aerial applicator may be substantial in absolute

terms, the more so since patients seem generally
unaware of hippocampal dysfunctions, even
though substantial deficits in performance, con-
sciousness or memory may be present.t® As a
practical matter these data reinforce previous
emphasis on the need for extreme caution in
handling the organophosphate pesticides.

Vv. Summary.

Mevinphos (Phosdrin) was found to inhibit
the amplitude of hippocampal evoked potentials
in unanesthetized squirrel monkeys with chron-
ically indwelling electrodes. The threshold dose
was 0.050 mg/kg and the maximal dose studied
was 0,200 mg/kg. Doses above 0.200 mg/kg
induced hippocampal seizures. Within the dose
range of 0.050 mg/kg to 0.200 mg/kg the ampli-
tude and duration of the inhibition were directly
proportional to dose. No peripheral signs of
poisoning, such as tremor or salivation, were seen
at doses of 0.200 mg/kg or under. The discussion
emphasizes that mevinphos produces changes in
brain function in the absence of the peripheral
symptomatology usually taken as indicators of
poisoning by aerial applicator personnel. There-
fore, it is concluded that exposure to mevinphos
may be unexpectedly hazardous since the aerial
applicators may be unaware that they have been
poisoned.





TRANSIENT BLINDNESS DUE TO THE COMBINED EFFECTS
OF MEVINPHOS AND ATROPINE

I, Introduction.

Organophosphate pesticide (OP) toxicity is of
continuing concern to aerial applicator personnel.
The toxic effects of OPs which may be seen in
the field are difficult to evaluate since most lab-
oratory tests are done with a single OP in isola-
tion while, in the “real world”, aerial applicator
personnel are exposed to a complex mix of agri-
cultural chemicals including several different
OPs and carbamates. Further, some aerial ap-
plicators may try to control effects of toxic doses
of OPs by use of atropine, pralidoxime (Proto-
pam, 2-PAM) and/or other drugs so that they
can continue working. Evaluation of the effects
of such drug mixtures is complex at best. At
the doses required to produce overt signs and
symptoms of poisoning, any given OP has a
wide spectrum of actions, chiefly, but perhaps
not entirely, related to its effects on cholinergic
functions. The same is generally true of the OP
antidotes such as atropine. Thus, combinations
of agonists and antagonists could result in un-
expected toxic effects, Experiments to investi-
gate these possibilities were initiated under Task
AM-B-73-TOX-15. Preliminary results were
unexpected and disquieting; sufficiently so that
early publication of this preliminary note was
deemed essential.

II. Methods.

Three squirrel monkeys were used. The ani-
mals had been implanted with chronically placed
intracerebral electrodes some months prior to
these experiments. Data derived from these
electrodes will be presented in another report.
At this time it is only necessary to note that
there were no signs of visual deficits in these
animals, although two electrode tracks passed
through the lateral geniculate nucleus, bilaterally.
In these experiments, the animals were placed
in a conventional 2-plate restraint. chair. Mevin-
phos (Phosdrin), the specific OP under test, was

injected intramuscularly in a dose of 0.4 mg/kg.
This dose was an estimated LD,.—which implies
a statistical probability that ten per cent of a
large group of animals tested at this dose would
die. This dose was deliberately chosen to in-
crease the likelihood of producing readily de-
tectable toxic signs. After development of
initial signs of OP poisoning, atropine was in-
jected intramuscularly in doses of 2 mg/kg,
repeated every three minutes, until the para-
sympathomimetic signs of OP poisoning van-
ished. The behavior of the animals was followed
for at least three hours after injection by three
to five observers in the laboratory. We checked
responses to touch and handling, to sound (tap-
ping the side of the cage, key jingling, etc.) and
to light (flashlight beams, sudden hand move-
ments, threatening gestures, etc.). All observers
participated in the testing and no result was re-
corded unless all observers agreed that a response
was present or absent.

III. Results.

All animals developed typical parasympa-
thomimetic signs within 2.5 min. of mevinphos
injection. These signs included salivation, pupil-
lary constriction, tremor and muscular weakness.
Within 3-4 minutes of injection all animals de-
veloped seizures. One animal had prolonged,
hard, tonic-clonic seizures which lasted for eight
minutes. This animal required artificial respira-
tion for about a minute during the peak of seiz-
ure activity. The parasympathomimetic signs
were also difficult to control with atropine and
this animal received a total dose of 30 mg/kg.
The other animals were less severely affected by
the insecticide and received less atropine; 15
mg/kg and 6 mg/kg respectively. In all animals
the initial period of severe symptoms lasted 15-30
minutes. For the next 2.5-3.0 hours the animals
in the observation cage appeared normal, though
weak. They responded to handling with their