Pituitary adenylate cyclase-activating polypeptide may function as a neuromodulator in guinea-pig adrenal medulla.
The role of pituitary adenylate cyclase-activating polypeptide (PACAP) in catecholamine secretion from dissociated adrenal chromaffin cells of the guinea-pig was investigated using amperometry, the patch clamp technique and immunochemistry. Pretreatment of adrenal chromaffin cells with 0.3-10 nM PACAP for 2 min resulted in enhancement of nicotine- and muscarine-induced secretions in either the presence of external Ca2+ ions or nominally Ca2+-free solution, with no change in basal secretion or the holding current at -60 mV in most of the cells tested. Pretreatment with PACAP augmented the muscarine-induced non-selective cation current, but did not affect the muscarine-induced outward current or nicotine-induced current. PACAP-induced enhancement of nicotine- and muscarine-induced secretions was suppressed by the simultaneous application of PACAP and the protein kinase inhibitors 100 microM HA1004 or 2 microM H89. Application of forskolin enhanced both muscarine- and nicotine-induced secretions, whereas application of a phorbol ester augmented the nicotine-induced secretion, but suppressed the muscarine-induced secretion in a reversible manner. Immunohistochemical analysis of adrenal medullae revealed that PACAP-like immunoreactivity was present in nerve fibres surrounding putative chromaffin cells. PAC1R-like immunoreactivity was distributed diffusely in the plasma membrane, whereas nicotinic ACh receptor-like immunoreactivity was concentrated at the plasma membrane near the nucleus, where the synapses were mainly localized. These observations suggest that PACAP in the guinea-pig adrenal medulla functions as a neuromodulator to facilitate ACh-induced secretion through a cAMP-protein kinase A-dependent pathway.
Inoue
M
M
Departments of Physiology and Anatomy, Fukuoka University School of Medicine, Fukuoka 814-0180, Japan. minoue@fukuoka-u.ac.jp
Fujishiro
N
N
Ogawa
K
K
Muroi
M
M
Sakamoto
Y
Y
Imanaga
I
I
Shioda
S
S
D000313:Adrenal Medulla / Q000187:drug effects / Q000502:physiology*; D000818:Animals; D002395:Catecholamines / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D004553:Electric Conductivity; D004789:Enzyme Activation / Q000502:physiology; D005260:Female; D006168:Guinea Pigs; D007120:Immunochemistry; D009479:Neuropeptides / Q000494:pharmacology / Q000502:physiology*; D018377:Neurotransmitter Agents / Q000494:pharmacology / Q000502:physiology*; D009994:Osmolar Concentration; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; D011493:Protein Kinase C / Q000378:metabolism; D011950:Receptors, Cholinergic / Q000502:physiology
D002395:Catecholamines; D009479:Neuropeptides; D018377:Neurotransmitter Agents; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; D011950:Receptors, Cholinergic; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C