Presynaptic Forms of Synaptic Plasticity

Vocabulary-style flashcards covering short-term and long-term presynaptic plasticity, including mechanisms of facilitation, depression, and hippocampal Mossy Fibre LTP.

Short-term (working) memory

A form of memory where synaptic strength is constantly adapting and current activity represents a history of previous activity, meaning not all information is retained for long periods.

Paired pulse depression

A type of frequency-dependent plasticity where synapses with a high initial release probability exhibit a decreased response to repetitive activation.

Paired pulse facilitation (PPF)

A form of plasticity occurring in synapses with lower release probability where a second stimulation (typically at a $50\,ms$ interval) produces a larger response than the first.

Residual Calcium

The build-up of calcium ions in the terminal that occurs when action potentials happen in quick succession because removal by ATP-dependent pumps, mitochondria, or the endoplasmic reticulum takes tens to hundreds of milliseconds.

Synaptotagmin

The calcium sensor for exocytosis that interacts with the plasma membrane proteins Syntaxin and SNAP-25, as well as the synaptic vesicle protein Synaptobrevin (VAMP).

2-Calcium Sensor Model

A model based on the deletion of Synaptotagmin-1, where a fast sensor controls synchronous release and a slow sensor controls asynchronous release at lower presynaptic calcium concentrations.

Vesicle depletion

A mechanism of synaptic depression where the readily releasable pool, consisting of approximately $5\%$ of total vesicles, is exhausted.

Inactivation of release sites

A mechanism of synaptic depression where release sites that have just undergone exocytosis become temporarily non-functional.

Tonic A1 Receptor Activation

An adenosine-mediated process at Mossy fibre-CA3 synapses that is negatively coupled to adenylate cyclase (AC) and produces a tonic reduction in release.

DCGIV

An mGluR agonist for mGluR2 and mGluR3 that blocks synaptic transmission and significantly reduces presynaptic calcium transients.

Trisynaptic Pathway

The hippocampal circuit consisting of: 1. Entorhinal Cortex (EC) to Dentate Gyrus, 2. Granule Cell (Mossy fibre) to CA3, and 3. CA3 to CA1 via SC/AC fibres.

Mossy Fibre (MF) LTP

A form of long-term potentiation induced by repeated high-frequency stimulation that is NMDAR-independent and dependent on a presynaptic increase in calcium.

$R$-type calcium channels

Calcium channels containing the $\alpha1E$ subunit; their interference affects the induction of Mossy Fibre LTP.

RIM1$\alpha$

A PKA substrate and synaptic vesicle protein binder (RAB3A) that is required for Mossy Fibre LTP; it facilitates GTP-dependent interaction between Rab3A and the active zone.

Kainate Receptor

A receptor whose activation leads to a potentiation of release, associated with an increase in presynaptic calcium and potentially CaMKII and cAMP mechanisms.

Short-term (working) memory

A form of memory characterized by constantly adapting synaptic strength where current activity reflects a history of previous activity, leading to retention of information for only a short duration.

Paired pulse depression

A frequency-dependent plasticity where synapses with high initial release probability show a decreased response to successive activations, indicating a temporary reduction in synaptic efficacy.

Paired pulse facilitation (PPF)

A plasticity mechanism in synapses with lower release probability that results in a larger response to a second stimulation (typically at a $50 \, ms$ interval) compared to the first.

Residual Calcium

The accumulation of calcium ions in the terminal due to successive action potentials, occurring because their removal by ATP-dependent pumps, mitochondria, or the endoplasmic reticulum takes tens to hundreds of milliseconds.

Synaptotagmin

The calcium sensor essential for exocytosis, which interacts with plasma membrane proteins Syntaxin and SNAP-25, as well as the synaptic vesicle protein Synaptobrevin (VAMP).

2-Calcium Sensor Model

A model proposing that a fast sensor controls synchronous release while a slow sensor manages asynchronous release at lower presynaptic calcium concentrations, informed by the deletion of Synaptotagmin-1.

Vesicle depletion

A synaptic depression mechanism where the readily releasable pool, which makes up about $5\%$ of total vesicles, gets exhausted with frequent stimulation.

Inactivation of release sites

A synaptic depression mechanism in which release sites that have experienced exocytosis become temporarily inactive.

Tonic A1 Receptor Activation

An adenosine-mediated process at Mossy fibre-CA3 synapses negatively linked to adenylate cyclase (AC), causing a tonic reduction in neurotransmitter release.

DCGIV

An agonist for mGluR2 and mGluR3 that inhibits synaptic transmission and significantly decreases presynaptic calcium transients.

Trisynaptic Pathway

The hippocampal circuit formed by: 1. Entorhinal Cortex (EC) to Dentate Gyrus, 2. Granule Cell (Mossy fibre) to CA3, and 3. CA3 to CA1 via SC/AC fibers.

Mossy Fibre (MF) LTP

A long-term potentiation form caused by repeated high-frequency stimulation, which is independent of NMDAR and requires a presynaptic calcium increase.

$R$-type calcium channels

Calcium channels characterized by the $\alpha1E$ subunit, whose interference affects the induction of Mossy Fibre LTP.

RIM1$\alpha$

A synaptic vesicle protein binder (RAB3A) essential for Mossy Fibre LTP, facilitating GTP-dependent interaction between Rab3A and the active zone.

Kainate Receptor

A receptor whose activation enhances neurotransmitter release, linked to increased presynaptic calcium and possibly involving CaMKII and cAMP mechanisms.