- binds to nicotinic & muscarinic ACh receptors

- nicotinic = on ganglion cells, cause excitation by opening chemically-gated channels

- muscarinic = all paraympathetic neuromuscular junctions w/ smooth muscle & neurogladular junctions 

- SLUD

- salivation, lacrimation (crying), urination, defication 

- NE & E bind to alpha & beta adrenergic receptors

NE: alpha > beta

E: alpha = beta

GPCR: receptor activates 2nd messengers; 2nd messengers determine excitation or inhibition 

Sympathetic Effects of E & NE Receptors

(alpha & beta)

Alpha 1 = vascular constriction, closure of sphincters of digestive & urinary tracts

Alpha 2 = parasympathetic receptor that gets inhibited during SYM activation

Beta 1 = increases metabolic activity of muscles, increases heart rate & force of contraction 

Beta 2 = relaxes respiratory smooth muscle, facilitates breathing 

1 - ACh

2 - Serotonin (5HT)

3 - Histamine

4 - Catecholamines: dopamine, epinephrine & norepinephrine

5 - Excitatory Amino Acids: glutamate, GABA, aspartate & NMDA

- receptors: nicotinic & muscarinic 

- degraded in synapse by acetylcholinesterase

- sites of action:

PNS: neuromusclar junction, sympathetic ganglia; CNS: neurons projecting from brainstem to many areas including PFC, basal forebrain, limbic system; associated w/ arousal  & cognition

- 13 receptors (major = 5HT1 - 5HT7); all are GPCRs (except 5HT3); 

- removed from synapse by reuptake (SERT)

- biosynthesized from tryptophan

- sites of action: 

CNS: neurons projecting from brainstem to ascending pathway (limbic system, PFC, striatum); regulation of mood, anxiety, sleep

- 5 receptors (D1 - D5; all are GPCRs)

- dopamine is cleared from the synapse by 2 mechanisms: reuptake (DAT1 & NET) & degradation (MAO & COMT)

- sites of action:

PNS: sympathetic terminals on smooth muscle; CNS: neurons projecting from brainstem to ventral tegmentum & substantia nigra, projecting to limbic system & PFC;

- associated w/ pleasure/reward, psychosis & movement

- receptors = GPCRs; 2 major classes: alpha (brain & periphery) & beta (mostly periphery)

- NE is cleared from the synapse by 2 mechanisms: reuptake (NET) & degradation (MAO & COMT)

- sites of action: 

PNS: sympatheic control of cardiac, smooth muscle, glands; CNS: neurons projecting from brainstem (locus coeruleus), projection to limbic system & PFC;

- associated w/ mood, arousal, cognition