1. Alan Yanahan
CPSC 270, 2009
Imidacloprid
A Neonicotinoid

2. History
Late 1970s: chemists at Shell Chemical Company laid the groundwork for the future synthesis of imidacloprid through their investigations of potential insecticides
1984: chemists as Nikon Bayer Agrochem create imidacloprid
First neonicotinoid insecticide registered for use

3. Imidacloprid Compared to nicotine Systemic insecticide
Less human toxicity and greater effectiveness against insects
Systemic insecticide
Used on a wide variety
of fruit and vegetable
crops
Used in termite control and
in flea control on pets

4. How Does Imidacloprid Work?
Have to understand the nervous system first

5. The Nervous System
Nerve cells transmit messages from one another by means of electrical impulses (action potentials)
The axon carries the message away from one nerve cell to the dendrites of another nerve cell

6. The Nervous System
Between the axon and dendrite is a gap referred to as the synapse
In order for the electrical message to cross the synapse, it must be converted into a chemical message

7. The Nervous System
When an electrical impulse reaches the end of an axon, it leads to the release of chemicals called neurotransmitters
These neurotransmitters bind with receptors on the dendrites of neighboring nerve cells to cause the generation of another electrical impulse
Enzymes break down neurotransmitters to prevent nerve cells from repeatedly firing

8. What Does This Look Like?

9. Vesicle releases acetylcholine (neurotransmitter) into nerve synapse
Acetylcholine binds with the enzyme acetylcholinesterase
Axon of pre-synaptic cell receives action potential and voltage gated Ca2+ channel opens
Voltage gated Ca2+ channel closes
Acetylcholine
Vesicle
Na+
Na+
Choline is released
Ca2+
Acetylcholine is released from nicotinic acetylcholine receptor
Calcium ions (Ca2+) enter axon
Nicotinic acetylcholine receptor opens
Na+
Ca2+
Ca2+
Acetate is released
Nicotinic acetylcholine receptor closes
Sodium ions (Na+) enter the dendrite and cause an action potential in post-synaptic cell
Acetylcholine binds with receptor (nicotinic acetylcholine receptor)

10. When Imidacloprid is Present in the Synapse
Imidacloprid mimics the molecular shape of the neurotransmitter acetylcholine
Acts on various nicotinic acetylcholine receptors to cause nerves to fire
Is not recognized by the enzyme acetylcholinesterase
Leads to tremors, convulsion, and death in insects

11. What Does This Look Like?

12. Acetylcholine binds with the enzyme acetylcholinesterase
Ca2+
Ca2+
Ca2+
Choline is released
Na+
Acetylcholine is released from nicotinic acetylcholine receptor
Na+
Acetylcholine
Nicotinic acetylcholine receptor opens
Na+
Acetate is released
Imidacloprid binds with the nicotinic acetylcholine receptor
Sodium ions (Na+) enter the dendrite to produce another action potential
Nicotinic acetylcholine receptor closes
Na+
Na+
Na+

13. Sources
Kreiger, Robert I. Handbook of Pesticide Toxicology 2nd Edition: Agents. Sheets, Larry P. Chapter 54—Imidacloprid: A Neonicotinoid Insecticide. San Diego: Academic Press, 2001
Silverthorn, Dee Unglaub. Human Physiology An Integrated Approach 4th Edition. San Francisco: Pearson Education Inc., 2007.