Neurotransmitters

Question 0

GABA

Answer 0

Neutral amino acid
Synthesized from glutamate by glutamic acid decarboxylase (GAD), mostly by interneurons
Major inhibitory NT in CNS
Ubiquitous location
Receptors: GABAa (inotropic), GABAb (metabotropic, baclofen is selective agonist for anti-plasticity in ALS, MS), GABAc (lo-subunit inotropic, high expression in retina, spinal cord, pituitary, not modulated by benzos, barbituarates)

Question 1

Glutamate

Answer 1

Major excitatory NT in CNS
Secreted by pyramidal cells
Binds to inotropic (AMPA, NMDA, Kainate) and metabotropic receptors
Plays a major role in synaptic plasticity and learning/memory
Xs glutamate can lead to excitotoxicity (AD, ALS, neuropathic pain)
Deficiency might lead to schizophrenia

Question 2

Acetylcholine

Answer 2

NT in NMJ, parasympathetic autonomic nervous system, CNS
Receptors: nicotinic (inotropic), muscarinic (metabotropic, M1-M5; M1,3,4,5-CNS, M2-heart, M3-smooth muscle)
Synthesized by choline acetyltransferace and broken down by acetylcholinesterase in synaptic cleft
Acetylcholinesterase Inhibitors indicated for AD, Dementia: donepezil, tacrine, galantamine, rivastigmine

Question 3

Dopamine (DA)

Answer 3

Catecholamine made by L-tyrosine
Degraded by MAO and COMT, reuptake by DAT (Dopamine Transporter)
Produced by substantia niagra, ventral tegmental area
Involved in behavior, cognition, motor activity, motivation, reward, addiction
D1 family (D1, D5) produces excitatory response
D2 family (D2, D3, D4) produces inhibitory response

Question 4

Norepinephrine

Answer 4

Made from L-Tyrosine via dopamine
Degraded by MAO and COMT
Reuptake by NET (Norepinephrine Transporter)
Metabotropic adrenergic receptors
Various actions according to cell type/receptor
Produced by locus coeruleus, caudal raphe nucleus
Involved in arousal, attention, focus.
Disorders: depression, ADHD, phobias, pain

Question 5

Serotonin

Answer 5

Made from L-Tryptophan
Degraded by MAO
Reuptake by SERT (Serotonin Transporter)
Activates 5-HT receptors
Produced by raphe nucleus
Involved in anger, aggression, mood, sleep, sexuality, appetite, pain

Question 6

Cannabinoid

Answer 6

Receptors: CB1 and CB2 (metabotropic)
CB1: inhibits GABA and Glutamate release, effect varies depending on brain region
Anandamine: endogenous CB1 agonist (attenuates pain), agonists-THC, CBD
CB2: immune system

Question 7

Opioid

Answer 7

Acts on metabotropic mu receptors
Analgesic effect
Drugs: morphine, codeine, heroin, buprenorphine
Endogenous opioids: endorphin, enkephalin, dynorphine, these peptides may be involved in opioid dependence/drug abuse, antidepressant activity, and chronic pain