Experiment Eight: Pharmacological Neuromodulation

Pharmacological neuromodulation

• Test effect of neuroactive compounds on neurons

• Only certain drugs affect neurons without danger– Nicotine– Glutamate– Ethanol

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Nicotine

• Acetylcholine receptor agonist

• Amplifies effect of Ach binding to receptors in synapses

• Causes a neuron to fire more

Monosodium glutamate

• Neurotransmitter• Dissolved in water,

glutamate ions released• Over 80% of synapses in

brain use glutamate as excitatory neurotransmitter

Ethanol• GABA receptor agonist• Unlike Ach receptor,

inhibits action potentials

• Causes a neuron to fire more slowly

Exercise 1: preparing neuroactive solutions

• Saline: combine 1.5 g table salt and 1.25 g baking soda in 250 mL distilled water

• Nicotine: dissolve tobacco from cigarette in saline

• Glutamate: dissolve MSG in saline

• Ethyl alcohol: mix 196 mL saline with 4 mL ethanol (2% EtOh)– Mix 12.5 mL 2% EtOh with

87.5 mL saline (0.25% EtOh)

Exercise 2: Cricket Cercal Ganglion Preparation

• Place crickets in freezer for 5 minutes to anesthetize

• Decapitate cricket at junction between head and thorax

• Insert electrode through abdomen into cercal ganglion

Exercise 3: Control Cercal Response

• Stimulate cerci by blowing from right or left side of cricket

• Record on Audacity or mobile device

• Record time and duration of stimulus (blowing) and side the stimulus was delivered (right or left)

Exercise 4: Testing Neuroactive Compounds

• Record with Audacity• Inject a few drops of

compound in abdomen• Stimulate cerci as in Ex. 3• Amplify and sketch traces

of stimulations on chart• Wash recording electrode

with saline• Repeat for nicotine,

glutamate, and both ethanol solutions

Trace Time

(Duration) Pattern and Brief Description of Movement

Left Side 1

Left Side 2

Right Side 1

Right Side 2