Selective activity of a proctolin analogue reveals the existence of two receptor subtypes.
1. The neuropeptide proctolin (Arg-Tyr-Leu-Pro-Thr) both potentiates neurally evoked contractions and causes contractures of insect skeletal muscle. In the hindleg extensor tibiae muscle of the locust, Schistocerca gregaria, the proctolin analogue [Afb (p-NO2)2]-proctolin is also able to potentiate neurally evoked contractions but is approximately 1,000-fold less effective in evoking contractures. 2. Proctolin and [Afb (p-NO2)2]-proctolin are equipotent in their ability to elevate the second-messenger inositol trisphosphate in isolated extensor tibiae muscle fiber membranes. 3. [Afb (p-NO2)2]-proctolin is approximately 1,000-fold less effective than proctolin in reducing the resting potassium conductance (GK) in extensor tibiae fibers. 4. We conclude that the action of proctolin on the extensor tibiae muscle is mediated by at least two receptor subtypes and that [Afb (p-NO2)2]-proctolin acts selectively on the receptor that potentiates neurally evoked contractions.
Baines
R A
RA
Sussex Centre for Neuroscience, University of Sussex, Brighton, United Kingdom.
Walther
C
C
Hinton
J M
JM
Osborne
R H
RH
Konopińska
D
D
D000818:Animals; D005121:Extremities / Q000294:innervation / Q000502:physiology; D005260:Female; D017952:Ganglia, Invertebrate / Q000166:cytology / Q000187:drug effects / Q000502:physiology; D006110:Grasshoppers / Q000502:physiology*; D066298:In Vitro Techniques; D007293:Inosine Triphosphate / Q000378:metabolism; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology; D009132:Muscles / Q000294:innervation / Q000378:metabolism / Q000502:physiology; D009479:Neuropeptides; D018377:Neurotransmitter Agents / Q000494:pharmacology*; D009842:Oligopeptides / Q000494:pharmacology*; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000187:drug effects / Q000378:metabolism; D018013:Receptors, Neuropeptide / Q000187:drug effects* / Q000378:metabolism
C102730:(3-(arginyl)amino-4-(4-nitrophenyl)butyryl)-leucyl-prolyl-threonine; D009479:Neuropeptides; D018377:Neurotransmitter Agents; D009842:Oligopeptides; D015221:Potassium Channels; D018013:Receptors, Neuropeptide; D007293:Inosine Triphosphate; C011536:proctolin