Exam 3 Neu 534

Locations of synapses

axosomatic

axodendritic

axo-axonic

Two types of axodendritic synapses

spine synapse

shaft synapse

Basic scheme of synaptic transmission

Acetylcholinesterase (AChE)

breaks down acetylcholine in synapse

Choline acetyltransferace (ChaT)

Converts choline and acetyl COA into acetylcholine

Nicotinic receptor

Ach

ionotropic

always excitatory

Muscarinic receptor

Ach

metabotropic

can be excitatory or inhibitory

Acetylcholine neurons in the brain

Basal forebrain cholinergic system

Brain stem cholinergic system

Vesicular glutamate transporter

Presence identifies neurons that use glutamate as a neurotransmitter

This is important bc glutamate is an amino acid that is found in all cells

Where are glutamatergic and GABAergic neurons found in the brain?

Everywhere, they are ubiquitous

Glutamatergic receptors as a whole

Can be ionotropic or metabotropic

Mostly excitatory, but some metabotropic are inhibitory

AMPA receptor

Ionotropic glutamate receptor

Permeable to sodium and potassium ions but not calcium ions

Fast but transient activation

NMDA receptor

Ionotropic glutamate receptor

Permeable to sodium, potassium AND calcium ions

Activate more slowly and persistently than AMPA receptors

Require BOTH glutamate and depolarization to fire - blocked by Mg ion before depolarization

Kainate receptor

Ionotropic glutamate receptor

Permeable to sodium and potassium ions but not calcium ions

Metabotropic glutamate receptors

Group 1 - excitatory, Gq protein

Groups 2 and 3 - inhibitory, Gi/Go protein

Glycine

Amino acid

Ionotropic, permeable to chloride ion

One of the major inhibitory neurotransmitters in ADULT vertebrate

Synapses are abundant in the spine and brain stem, but also found in cortex, thalamus, and hippocampus

Glycine transporters

GlyT1 - highly expressed in areas correlated with glutamatergic terminals (like neocortex, hippocampus)

GlyT2 - higher expression in spinal cord, brain stem, cerebellum

GABA

inhibitory, but you already know that

“gamma-aminobutyric acid”

derived from glutamate

GABA-gated chloride channel

If allowed to travel freely, chloride (Cl-) will enter the cell until the membrane potential is -80 mV

GABA-gated chloride channel allows this to occur when GABA binds, hyperpolarizing the cell

GABAergic neurons

Catecholamines

Neurotransmitter class, all share catechol structure

dopamine, norepinephrine, and epinephrine

How are catecholamines inactivated

They are reuptaken into the presynaptic neuron by transporters, NOT degraded

Tyrosine hydroxlase

performs first step in creation of all catecholamines: conversion of tyrosine to dopa

Synthesis of catecholamines

Dopamine neurons location in the brain

Substantia nigra and ventral tegmental area

Locus Coeruleus

Nucleus in the pons where noradrenergic neurons are located

Relatively few neurons, but they project WIDELY across the CNS

Epinephrine neurons location in the brain

Used as a neurotransmitter by a cluster of neurons in the medulla

Project to hypothalamus, thalamus, and spinal cord

Tryptophan

Used to make 5-HTP, which is then used to make 5-HT (serotonin)

Raphe nuclei

Location of serotonin neurons

Distributed along midline of the brain stem

Project diffusely across CNS

Tuberomammillary nucleus of the hypothalamus

Cluster of histamine neurons

What category of receptor are histamine receptors

They are GPCRs/metabotropic receptors

Structure of metabotropic receptors

Seven transmembrane domains

Single subunit

Intracellular segment and 3-4 loop binds to GTP binding protein

Extracellular loops 2-3 and 6-7 bind to neurotransmitter

Integration of neurotransmitter signal