Abstract
Proctolin (Arg-Tyr-Leu-Pro-Thr) and proctolin analogs modified at position 1, 2, or 5 caused dose dependent contractions of Blaberus fore- and hindgut. The varying contractile effects between both tissues revealed the possible presence of receptor subtypes as identified by [GABA1]-proctolin. A single population of binding sites (Kd approximately 100 nM) was deduced from Scatchard analysis. In addition, nanomolar concentrations of proctolin induced a dose-dependent hydrolysis of phosphoinositides (PIns) augmented by GTPgammaS (1 microM) on foregut membranes but no accumulation of cAMP. Proctolin induced contractions are likely mediated via a phospholipase C linked to a heptahelical receptor bound to heterotrimeric G-proteins.
MeSH terms
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Adenylyl Cyclases / metabolism
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Animals
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Cell Membrane / chemistry
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Cell Membrane / drug effects
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Cell Membrane / enzymology
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Cockroaches
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Cyclic AMP / metabolism
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Dose-Response Relationship, Drug
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Hydrolysis / drug effects
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Neuropeptides*
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Neurotransmitter Agents / pharmacology*
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Oligopeptides / pharmacology*
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Phosphatidylinositols / metabolism
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Protein Binding / drug effects
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Receptors, Neuropeptide / classification
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Receptors, Neuropeptide / metabolism*
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Receptors, Neuropeptide / physiology
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Second Messenger Systems / drug effects
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Stomach / chemistry*
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Stomach / cytology
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Stomach / drug effects
Substances
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Neuropeptides
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Neurotransmitter Agents
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Oligopeptides
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Phosphatidylinositols
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Receptors, Neuropeptide
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proctolin
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Cyclic AMP
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Adenylyl Cyclases