long term potentiation

1. LONG TERM
POTENTIATION
A S H M I N A D H I K A R I

2. DEFINITION
• Long term potentiation (LTP) is a system for memory formation in molecular
basis.
• LTP is persistent strengthening of synapse that leads to a long lasting increase
in signal transmission between neurons.
• It occur when a neuron shows an increased excitability overtime due to a
repeated pattern, behaviour or response.

3. CRITERIA FOR LTP
1) NMDA receptors must be activated
2) the post synaptic neuron must be partially depolarized.

5. PHASES
 LTP occurs in two phases
I. Early phase : Ca++ ion initiate signal pathway which activates various
protein kinesis which enhance synaptic connection between two neurons. It
involves in increase sensitivity of synapse with out any new gene
transcription or mRNA translation
II. Late phase: it involve requiring new gene transcription and mRNA
translation. Thus, results in an increase in the number of AMPA receptors
accompanied by an increase in the size of synaptic connection.

6. PROPERTIES OF LTP
1) Specificity : if some of the synapse onto a cell have been highly active and
others have not only the active one become strengthened. However
establishing LTP at one synapse does briefly facilitate the formation of LTP at
near by synapses on the same dendrites.
2) Co-operativity : Nearly simultaneous stimulation by two or more axon
produces LTP much more strongly than does repeated stimulation by just one
axon.
3) Associativity : pairing a weak input with a strong input enhance later response
to weak input.

7. RELATION TO BEHAVIOURAL
MEMORY
• Long term potentiation of synapses in cell culture seems to provide an elegant
substrate for learning and memory. The contribution of LTP to behavioural
learning is learnt at the level of whole organism. It also play a crucial role in
fear processing.
• E.g.: if a mouse is placed in pool of murky water, it will swim about it finds a
hidden platform to climb out on. On repetition, the mouse soon learns to locate
the platform more quickly.

8. LONG TERM DEPRESSION
• A long term decrease in the
excitability of a neuron to a
particular synaptic input caused by
stimulation of terminal bottom
while the post synaptic membrane
is hyperpolarized or depolarized.
• Higher level of CA++ in Cerebellar
cortex leads to LTD.
• LTD is associated with shrinkage of
dendrites and decreased number of
synaptic receptors