Neurotransmitters 2

Glutamate receptors

(ionotropic and metabotropic)

ionotropic: AMPA, NMDA, Kainate
metabotropbic: mGLuRs

AMPA receptors

glutamate receptor that is permeable to Na and K

very fast, lets more NA in than K leading to rapid depolarization

fast excitatory transmission in the CNS

excitation helps activate NDMA

NDMA receptors

permeable to Na and K and Ca

voltage gated: no flow unless depolarized since magnesium is blocking it

needs a certain level of depolarization to remove magnesium block and allows passage of Na, K and Ca. causes slower long lasting excitation

AMPA activation helps remove magnesium: glycine and glutamate then bind to activate receptor: excitatory effect

Glutamatergic transmission

AMPA and NDMA receptors are both activated becuase glutamate activates AMPA which activates NDMA receptors

GABA receptors

(synthesis, 3 types)

neurons make GABA from glutamate

3 types receptors

GABA A

GABA B

GABA C

GABA A receptor

ionotropic: Cl- channels hyperpolarizing, fast inhibition

GABA B receptor

Metabotropic: changes Ca and K levels slow inhibiition opening K channels, hyperpolarizing

GABA C receptor

ionotropic Cl- channels (found in the retina) not mentioned again

functions of GABA

main inhibitory neurotransmitter reduce excitability of neurons have sedative effect

ex. molecules like benzodiaepine (affect freq passage opens), barbituates (duration remains open), ethanol

agonists work too. all block seizures, relaxation and sleep

alll bind. to different sites on the receptor  increase fire or duration of Cl- channel opening when GABA is present

leading to stronger inhibitory potentials and thus certain behaviors

ACh receptors (acetylcholine)

types

Nicotinic

Muscarinic

Nicotinic receptor

ACh receptor ionotropic and excitatory effect

Muscarinic receptor

ACh receptor is metabotropic and is slower. effects are excitatory or inhibitory

How to distinguish receptor types

By Actions of diff drugs/ testing different drugs interact with receptors:

nicotine an agonist on skeletal msucle, if used on heart will have no effect on the heart (meaning muscle of heart has a different receptor that effects it)

Muscarine (from positous mushroom): a agonist for the heart, no effect on the skeletal muscle

By the affects of selective antagonists

Curare: arrow tip poision inhibits Ach at nicotinic receptors leading to paralysis of skeletal muscles

Atropine: from belladonna inhibitis ach and has parasynpathetc effects on the heart and organs at muscarinic receptors

ACh differential effects (nicotinic ACh recptor vs Musacarnic ACh receptor)

skeletal msucle:

causes muscle contraction

Na enters the cell - depolarizes excitatory

heart muscle

muscarnic

g coupling slower opening K channels hyperpolzriing and ihbits

slowng heart msucle contractions

Monoamines

Catecholamines: DEN

Indolemaines: MS

Synthesis of Cathecolamines

(precursors and enzymes flow)

Tyrosine 

enzyme

Ldopa

enzyme 2

Dopamine

enzyme

Norepinephrine

enzyme 2

Epnephrine

Dopamine receptors

(types, which exct, or inhib) function

4 subtype receptors

D1 and D2 are exicitatry

D2 D3 and D4 and inhibtory

excstiance of D6 and 7 being researched

• movement, reward, learning, etc many

Norepinephrine NE receptors

(types, their function, general function

5 subtypes all metabotropic:

a1, a 2, b1-3

a1: excitatory (bp raising, fight or flight)

a2: (feedback system presynaptic neuron produce more NT, inhibiting release)

beta adrenergic receptors

b1-3 (similar: heart rate, smooth muscle relaxation, metabolism?)

general: mood, arousal. and sexual behaviour

release in Symp NS → fight/flight

Serotonin receptors

14 types of 5-HT receptors  

all but one type is metabotropic receptor

effects: sleep, mood, sexual behaviour, anxiety. specifc effect depends on which receptor subtype 

not focusing on the mechanism

g protein spilts and goes   somewehre

(at one time believed that low serotonin causes desperssion, by tested this by blocking trypofan and doesnt cause depression) drugs aid the functioning of NT. 

some drgus raise serotonin levels decreasing depression but reason behind in moe complicated doesnt mean lack of serotonin was the problem 

serotnin has diverse effects, many different o