Exam 3

Lesioned different parts of the brain: -learning/remembering maze was not impaired by local cortical legion anywhere BUT: larger the lesion, greater the impairment (engram is everywhere)

made first intracellular recordings of APs from hippocampal neurons (in cats) ended up working with aplysia later on with Tauc

• abdominal ganglion has only about 300 neurons • neuron cell bodies are big • identical organization of nervous system in all aplysia

intracellular recordings from neurons found ones that got EPSP when they stimulated nerve 1, but not when stimulated nerve 2 conclusions: a cell w/ an axon in nerve 1 makes excitatory synapse on test nuron; no neurons w/ an axon in nerve 2 directly synapse onto test neuron

stimulate nerve 2 repetitively for a few seconds test to see if amplitude of response to stimulating nerve 1 was larger or smaller (was larger)

repetitive stimulation of anueron leads to either transient increase (facilitation) or decrease (depression) in response amplitude

repetitive stimulation of one neuron changes the response to stimulation of another neuron

gill and siphon: respiratory organis gentle tap to siphon causes gill to withdraw repetitive taps causes less and less response (habituation)

behavioral event analogous to heterosynaptic facilitation gentle tap to siphon causes gill to withdraw give electrical shock to tail responses to sphon tap is larger, more rapid, longer lasting gill withdrawal

sensory neurons respond to siphon tap motor neurons cause gill to withdraw tail sensory neurons contact interneuron 5-HT

habituation occurs at sensory motor synapses

habituation: decrease in release probability of NT release sensitization: increase in release probability

single shock produces short term sensitization only multiple shocks gives changes that are larger and persist for days

L29 facilitator interneuron releases serotonin

serotonin (5-HT), cAMP, PKA

PKA phosphorylates voltage independent “leak” K channel (gKs) and shuts it off, slowing spike repolarization calcium channels stay open longer so more calcium enters more transmitter is release, thus sensitization

motor neuron and one or more sensory neurons in a cell culture directly apply serotonin with a pipette

new protein synthesis protein synthesis inhibitor Anisomycin prevents long term sensitization to serotonin

single sensory neuron innervates 2 motor neurons apply 5 pulses of 5-HT only near MN2 only SN-MN2 synapses facilitated (something beyond transcription/translation required for sensitization)

synpases that see 5x serotonin are marked: 1) RNA/protein synthesis are near nucleus, but the new protein is only incorportated into synapses that were marked by 5HT 2) RNA synthesis is in the nucleus, but protein synthesis occurs in marked-presynaptic terminals, not in cell body (CORRECT)

put photoswitchable tag on newly translated proteins initally glows green, turns red w/ UV light (all pre-existing protein glows red) look for where the new green proteins are RESULT: only branches that saw 5-HT make new protein, even though mRNA is in all branches

forward genetics • feed EMS to male flies (random mutations) • cross to WT females • outcross offspring separately (offspring each carry different mutations) • make inbred lines of new mutations • test for any phenotype of interest

• before odorant-shock pairing, flies have no preference for odor A or B • associate odor A with electric shock • WT flies choose odor A

-performance index = (flies avoiding odor A - flies avoiding odor B)/total flies index = 1: learning; index = 0: no learning