Excitatory Neurotransmission – Boosting Neural Activity in Insects

Understanding excitatory neurotransmission provides critical insights into how the nervous system modulates sensory responses. In this experiment, you'll explore how nicotine—an agonist of excitatory nicotinic acetylcholine receptors—can significantly increase neural firing rates, highlighting key mechanisms underlying sensory processing.

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About the Experiment

What Will You Learn?

How excitatory neurotransmitters influence neural activity in insect sensory systems.
Techniques for recording and analyzing neural responses to chemical stimulation.
The specific effects of nicotine on the cricket cercal sensory system.

Background

Neurotransmitters modulate sensory inputs by increasing or decreasing neuron firing rates. In crickets, nicotine mimics the excitatory neurotransmitter acetylcholine, significantly amplifying neural responses in the sensory cercal system, which detects air movements. This experiment lets you observe how nicotine enhances neural signaling, illustrating fundamental excitatory mechanisms.

Procedure

Preparation:
1. Briefly anesthetize a cricket by placing it in ice water.
2. Secure the cricket onto a stable surface, leaving the cerci unobstructed.
Electrode Placement:
1. Insert the recording pin into the abdomen along the cricket’s midline, just in front of the cerci.
2. Insert the ground pin along the midline farther forward (no gel is needed).
Baseline Recording:
1. Record baseline neural responses by stimulating cerci with gentle air puffs.
2. Capture multiple trials to establish a consistent baseline response.
Neurotransmitter Testing:
1. Nicotine Application:
2. Prepare a nicotine solution from tobacco leaves soaked in water.
3. Using a small syringe, inject a tiny drop into the cricket’s abdomen near the recording electrode.
4. Record neural responses after nicotine application.