Neural Modulation – Discover How Neurotransmitters Shape Sensory Responses

Understanding neurotransmitter modulation is crucial for grasping how substances influence brain and sensory function. Using a cricket's sensitive sensory system, this experiment demonstrates how substances like nicotine and MSG can dramatically alter neural responses, providing insight into the complexity of neurotransmitter action across different species.

Devices and Accessories2

About the Experiment

What Will You Learn?

How sensory neurons respond to air vibrations.
How inhibitory and excitatory substances modulate neural activity.
The contrasting effects of MSG and nicotine, which act on neurotransmitter receptors, on the cricket’s wind-sensing circuit.

Background

Crickets detect wind vibrations using cerci—specialized sensory organs sensitive to air movements. These cerci trigger neural activity that can be influenced by chemicals that act on neurotransmitter receptors. Interestingly, MSG typically inhibits neuronal activity in crickets, while nicotine usually enhances it, illustrating how neurotransmitters can have diverse effects in different organisms.

Procedure

Preparation:
1. Briefly anesthetize a cricket in ice water and secure it onto a stable platform without covering the cerci.
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 activity using your Neuron SpikerBox.
2. Stimulate cerci gently with air puffs to establish a baseline neural response.
Neurotransmitter Testing:
1. MSG Application:
2. Dissolve MSG in water. Using a small syringe, inject a tiny drop into the cricket’s abdomen near the recording electrode.
3. Record neural activity and compare with baseline.
4. Nicotine Application:
5. Prepare a nicotine solution from soaked tobacco leaves.
6. Inject a tiny drop into the abdomen near the recording electrode and compare with baseline.

Results & Analysis

MSG typically decreases neural activity, while nicotine usually increases activity.

Discuss potential reasons for the observed inhibitory effects of MSG and the excitatory effects of nicotine.

Draw the pathway from a wind-sensing hair on a cercus, along its sensory neuron, to the synapse in the cricket’s nerve cord where the message is passed on. Mark where your recording electrode sat and where you think MSG and nicotine act.

NGSS alignment

Performance expectations

Chemical synaptic signaling; drugs alter information processing.

MS-LS1-8 Gather and synthesize information that sensory receptors respond to stimuli by sending messages to the brain for immediate behavior or storage as memories.
HS-LS1-2 Develop and use a model to illustrate the hierarchical organization of interacting systems that provide specific functions within multicellular organisms.

Science and engineering practices

2 Developing and Using Models

Draw the pathway from a cercal hair through its sensory neuron to the synapse in the nerve cord, and mark where you recorded and where you think the chemicals act.
3 Planning and Carrying Out Investigations

Record the cerci's response to air puffs, then inject MSG and nicotine.
4 Analyzing and Interpreting Data

Compare activity after each chemical with the baseline.
6 Constructing Explanations and Designing Solutions

Explain why MSG lowers and nicotine raises the cerci's response.

Crosscutting concepts

Cause and Effect

Chemicals alter firing.
Structure and Function

The receptor a chemical binds decides the direction of its effect.

Disciplinary core ideas

LS1.D Information Processing

Chemical transmission.
LS1.A Structure and Function

Membrane receptors and channels.

Performance expectations, crosscutting concepts and core ideas from Hands-On Neuroscience Curriculum Overview, Unit 1, module 1.4, whose core lab this is. The practices are the ones this page asks students to do.