Table 1.

Summary of the Chemical Messengers So Far Implicated in Human β-Cell Function

Messenger	Mode	Receptor	Action	References
ACh	Paracrine	M3	Increases Ca2+-dependent exocytosis via IP3 generation
			Increases Ca2+-sensitivity of exocytosis via PKC	64
Somatostatin	Paracrine	SSTR 2 and 3	Activation of G protein-gated inward rectifier K+ channels (GIRK)
			Hyperpolarization and decreased hormone release	65
Insulin	Autocrine	IR A and B	Engagement of PI3K reduces pre-prepropinsulin gene expression
			Suppressed hormone release	72, 73
ATP	Autocrine	P2X	Opening of the P2X channel pore allowing influx of Ca2+ and Na+
			Depolarization and exocytosis	79, 81
GABA	Autocrine	GABA(A) and GABA (B)	GABA(A) stimulate hormone release
			GABA(B) suppress hormone release	83, 84
Dopamine	Autocrine	D2R	Gi-coupled receptor leading to inhibition of adenylate cyclase
			Suppressed hormone release	85, 86, 88

D2R, dopamine 2 receptor; IP3, inositol triphosphate; IR, insulin receptor; M3, muscarinic acetylcholine receptor M3; PI3K, phosphatidyl phosphate 3 kinase; PKC, protein kinase C; SSTR, somatostatin receptor.