1. Long-term behavioural effects of
developmental exposure to
organophosphates
Ora Kofman
Department of Psychology
Zlotowski Centre for Neuroscience
Ben-Gurion University of the Negev
Beer-Sheva

2. Why is pesticide exposure in children
different from exposure in adults?
Neurotransmitters and related enzymes
have neurotrophic roles.
Cholinergic markers appear at the same
time that synaptogenesis, pruning, thalamic
and cortical stratification occur in the
developing brain. The high level of AChE
prior to the development of cholinergic
projections, suggests that it has a role in
neuronal growth.

3. Formation of synapses continues after birth and is influenced
by sensory stimulation and learning, drugs and toxins.
migration

4. Neonatal rats injected unilaterally with basal forebrain
ACh neuronal toxin on day of birth and postnatal day 2
show reduced cortical thickness.
Cerebral Cortex 1998
8:142-155

5. Control Lesioned Control Lesioned
Neonatal rats injected with ACh neuronal toxin on
P0 and P2 show reduced number of dendrites (A vs B)
dendritic spines (C vs D) and axons (E vs F).
Robertson et al. Cerebral Cortex 1998 8:142-155

6. Prenatal exposure to OP pesticide alters cortical thickness and gene expression

7. Exposure
Accidental Chronic
poisoning low dose
exposure

8. % cases recorded
Plants Rat Cleaning Medicine Pesticide Kerosene
poison agents and drugs
Mush-
rooms
Sri Lanka 8 8 51 12
Over age 30
includes
suicide attempts
Senanayake &
Karalliedde, Forensic
Sci Int 1988
Trinidad 9.4 21.8 15.9 19.5
Children <16
Pillai, Boland,
Jagdeo and Persad,
West Indian Med J.
2004
India 9 6.7 20.9 42.5
Children 1-3
Sarker, Ghosh,
Barik Indian J
Public Health
1990

9. Who is at risk?
•In urban and rural areas high levels of
pesticides have been found in blood
of pregnant women and cord blood at birth.
•Children in agricultural communities:
Drift from fields
Pesticides on clothes, shoes of parents
•Inner city children have higher exposure
than children in the suburbs.
Dilworth Bart and Moore, Child Development, 2006
Castorina et al. Env Health Perspect 2003
Whyatt et al. Toxicol Appl Pharmacol 2005
Curwin et al. Environmental Health 2007

10. Exposure during pregnancy
Young et al. Neurotoxicology 2005 :
Total metabolite levels of OP pesticides associated
with abnormal reflexes on the Brazelton assessment.
Abnormal reflexes:
Rooting
Passive Leg Resistance
Incurvation
Moro

11. Exposure during pregnancy
Eskenazi et al. Env Health Perspect 2007
Followup of children exposed in utero to OPs at
6, 12 and 24 months.
•Association between OP metabolites and lower
scores on Mental Development Index of Bayley.
•Association between OP metabolites and PDD
(Pervasive Developmental Disorder) scale
of CBCL (Child Behavioral Checklist) at 24 months.
•No effects on attention deficit scale of CBCL.

12. Exposure during pregnancy
Grandjean et al., Pediatrics 2006
Impaired visual memory (Stanford Binet
drawings) and copying
drawings (visuo-constructive, visuo-spatial).
Rauh et al. , Pediatrics 2006
Inner city children followed
from birth
36 months
Psychomotor development
index lower in group with high
prenatal chlorpyrifos (CPF)
exposure: cognitive and
psychomotor delays.
CBLC: Attention disorder
associate with prenatal CPF
exposure.

13. Exposure during childhood
Grandjean et al., Pediatrics 2006
Participants: Children in Ecuador
whose mother work in floriculture.
Simple reaction time is slower in
children with higher levels of urinary
OP metabolites.
Ruckart et al. Env Health Perspect 2004
1-2 years after exposure to methyl parathion:
Increased impulsivity and conduct disorders
Sanchez Lizardi et al. J. Pediatric Psychol 2008
High OP metabolites associated with more errors in
Wisconsin Card Sorting but BETTER concept formation.

14. Exposure during childhood
Rohlman et al., Neurotoxicology
2005
Slower motor performance (tapping)

15. Summary: Exposure to OPs during early development:
from birth to childhood
Foetus -Infant Child
Lower gestational age
Visuospatial impairment
Abnormal neonate reflexes
Impaired psychomotor Attention deficit
development
Motor deficit
Impaired mental development
Social skill deficit (PDD)

16. Motor Inhibition and Learning Impairments in School-Aged
Children Following Exposure to Organophosphate Pesticides in
Infancy
ORA KOFMAN, ANDREA BERGER, ALI MASSARWA, ALON FRIEDMAN, AND ABED
ABU JAFFAR
Pediatr Res 60: 88–92, 2006

17. Hospitalizations under age 3 with acute
poisoning at Soroka University Medical
Center. More than 90% of poisonings
reported were in children from the Bedouin
sector.

18. Statue and Knock-Tap tests from
NEPSY battery.
Inhibition and ability to ignore distraction
Stand like a statue with eyes closed with one hand up as if holding a
flag (75 seconds) while experimenter makes different noises.
Lose points for movements, eye opening, talking and other rule breaks.
Knock – Tap. Experimenter sits opposite child and performs
hand movements: strike table with palm down, or fist.
Child has to perform the alternate movement and in some
cases no movement at all.
Inhibition of pre-potent response.

19. Statue
Number of points (Mean + SEM)
Knock Tap
29 *
27
25
23
21
19
17
15
P
-K
e
P
-O
en
l
O
ro
l
os
ro
t
on
er
t
on
C
K
C
Children with OP poisoning had lower scores than age and sex
matched controls. No effect on Knock-Tap test.

20. 12 Control OP
11 OP Verbal list
Words recalled (Mean + SEM)
learning and
10
9
8
7
recall
6
5
4
Children from
3 both poisoning
groups had
List A-1 List A-2 List A-3 List A-4 List A-5 List B List A-6
12
11
Control K
poorer recall
in acquisition
Kerosene
Words recalled (Mean + SEM)
10
9
8
phase BUT
7 there was no
difference in
6
5
4 delayed recall
or recognition.
3
List A-1 List A-2 List A-3 List A-4 List A-5 List B List A-6

21. Future Directions
Exploring Gene x exposure interactions in rodents
AChE I inhibitors or stress induce alternate splicing
of the enzyme AChE to its rare readthrough form
AChE –R (Soreq and colleagues).
DFP – Kaufer et al. 1998; Meshorer et al. 2002
Soman- Perrier et al. 2005
Diazinon– Jameson et al. 2007
Restraint, but not swim stress – Perrier et al. 2005
Swim stress – Kaufer et al. 1998

22. Forced swim test- prolonged immobility is
regarded as enhanced depression (helplessness)

23. Stages of brain development dependent on induction of genes
240
at different stages. Development is influenced by substances
220
such as neurotransmitters and enzymes.
200
180
Immobility (sec) swim stress
160
140
120
100
80
60
40
20
0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1
AChER CTX RQ PCR
The greater the AChER levels in cortex, the less
immobility depression) is found.

24. Elevated plus maze: Rodent
test for anxiety
The less time in the open
arms of the maze, the more
anxious the mouse is.
r=-.21 ,p<.05
2.2
2.0
1.8
1.6
AChE-R cortex
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
-2 0 2 4 6 8 10 12 14 16 18 20
Entries open arms

25. Future Directions
Exploring Gene x Exposure Interactions in rodents
Injection of DFP in mice at age 4-10 or 14-20 days
•Increased learned anxiety on 2nd exposure to
the elevated plus maze.
•Females but not males show poor passive avoidance
despite evidence of good retention.
•Females but not males are impaired in complex
discrimination learning involving set shifting.
•Male but not females show anhedonia (reduced
preference of a sweet solution) and this effect seems
to be strain dependent.

26. THANKS
Ali Massarwa
Andrea Berger, PhD
Amneh Atamneh
Alon Friedman, MD PhD
Guy Ben Bashat
Abd Abu Jaffar, MD
Uri Livneh
Amir Dori, MD PhD Tamar Lin
Israel Science Foundation Or Duek
National Institute for Psychobiology in Israel