Somatostatin modulation of adenosine receptor coupled G-protein subunits in the caudate nucleus of the rat.
5'-(N-ethylcarboxamido)-adenosine (NECA) and N-[(R)-(phenylisopropyl)]-adenosine (PIA) were incubated in an adenylate cyclase assay of a particulate fraction of caudate-putamen tissue of the rat in order to examine the effect of somatostatin on adenosine receptors coupled adenylate cyclase subunits in vitro. Somatostatin was able to inhibit the enhancement of cyclic AMP formation induced by NECA in the presence of the hydrolysable guanine nucleotide guanosine-triphosphate. The adenosine receptor antagonist 8-cyclopentyl-1,3-dipropylxanthine as well as the somatostatin receptor antagonist cyclo (7-aminoheptanoyl-Phe-D-Trp-Lys-O-benzyl-Thr) did not influence somatostatin induced inhibition of NECA-activated adenylate cyclase. Somatostatin did not modulate the effect mediated by the A-1 adenosine receptor agonist PIA. Both pertussis toxin and cholera toxin activated striatal adenylate cyclase acting on the guanine nucleotide regulatory subunit of the enzyme. The stimulation induced by pertussis toxin was antagonized by somatostatin, while in presence of cholera toxin somatostatin enhanced cyclic AMP formation. These results suggest that somatostatin acts through a stimulatory as well as an inhibitory guanine nucleotide regulatory protein subtype to affect probably postsynaptic A-2 adenosine receptor coupled adenylate cyclase activity.
Moser
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Department of Neurology, Medical University of Lübeck, FRG.
Klose
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D000241:Adenosine / Q000031:analogs & derivatives* / Q000494:pharmacology; D019830:Adenosine-5'-(N-ethylcarboxamide); D037361:Adenylate Cyclase Toxin; D000262:Adenylyl Cyclases / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D002421:Caudate Nucleus / Q000187:drug effects* / Q000378:metabolism; D002772:Cholera Toxin / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D005260:Female; D019204:GTP-Binding Proteins / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000378:metabolism; D006165:Guanylyl Imidodiphosphate / Q000378:metabolism; D008969:Molecular Sequence Data; D037342:Pertussis Toxin; D010660:Phenylisopropyladenosine / Q000494:pharmacology*; D058914:Purinergic Antagonists; D051381:Rats; D017208:Rats, Wistar; D011983:Receptors, Purinergic / Q000187:drug effects*; D017481:Receptors, Somatostatin / Q000037:antagonists & inhibitors; D015290:Second Messenger Systems / Q000187:drug effects*; D013004:Somatostatin / Q000031:analogs & derivatives / Q000494:pharmacology*; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D037361:Adenylate Cyclase Toxin; D058914:Purinergic Antagonists; D011983:Receptors, Purinergic; D017481:Receptors, Somatostatin; D010566:Virulence Factors, Bordetella; C036876:cyclo(7-aminoheptanoyl-phenylalanyl-tryptophyl-lysyl-threonyl); D010660:Phenylisopropyladenosine; D006165:Guanylyl Imidodiphosphate; D019830:Adenosine-5'-(N-ethylcarboxamide); D013004:Somatostatin; D006160:Guanosine Triphosphate; D002772:Cholera Toxin; D037342:Pertussis Toxin; D019204:GTP-Binding Proteins; D000262:Adenylyl Cyclases; D000241:Adenosine