Page 100 - Color_Atlas_of_Physiology_5th_Ed._-_A._Despopoulos_2003

B. Adrenoceptors
Norepinephrine Natural agonists Epinephrine

Agonists: Salbu-
Phenylephrine Clonidine Iso-
proterenol tamol
II
Antagonists:
Prazosin Yohimbine Atenolol

Adrenergic
receptors: 1 2 3 4 Adrenergic Transmission
α 1 α 2 β 1 β 2
G q G q G o G i G s G s
PIP 2 cAMP cAMP
cAMP
K + PLC β +
DAG Ca 2+ K PKA PKA
IP 3
PKA
PKC Plate 3.6
Ca 2+ ?
Ca 2+

Hyper- 2+ 2+ Hyper- 2+ 2+
polarization [Ca ] i [Ca ] i polarization [Ca ] i [Ca ] i

Inhibition of
gastrointestinal
motility α 1 Inhibition of α 2 β 1 β 2
exocytosis Drives heart Dilatation of
Contraction of α 1 or secretion • Vessels
• Blood vessels • Salivary glands • Bronchioles
• Bronchioles • Insulin • Uterus
• Sphincters • Norepinephrine Renin release etc.
• Uterus • Acetylcholine
etc. etc.

!
rotransmitters in the autonomic nervous sys- nal secretion. Nitric oxide (NO) is liberated
tem. VIP and acetylcholine often occur jointly from nitrergic neurons (! p. 278)
(but in separate vesicles) in the parasympa-
thetic fibers of blood vessels, exocrine glands,
and sweat glands. Within the gastrointestinal
tract, VIP (along with nitric oxide) induces the
slackening of the circular muscle layer and
sphincter muscles and (with the co-transmit-
ters dynorphin and galanin) enhances intesti- 87

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