The release of octopamine and proctolin from an insect visceral muscle: effects of high-potassium saline and neural stimulation.
The release of octopamine and proctolin from the oviduct visceral muscles of the locust, Locusta migratoria, has been investigated. Salines containing elevated potassium concentrations (100 mM) were capable of releasing both octopamine and proctolin, although the proportion of the total store of octopamine released (19%) was much greater than that of proctolin (0.4%). The high potassium-induced release of octopamine was calcium-dependent. Electrical stimulation of the oviducal nerves also resulted in the release of octopamine and proctolin. The release of both substances was frequency-dependent with maximum release of octopamine occurring at about 5 Hz, and maximum release of proctolin at 30 Hz. Neural stimulation was a more effective means of inducing proctolin release than was high-potassium saline, with 6.3% of the total store of proctolin released with 5 min stimulation at 30 Hz. The neurally stimulated release of proctolin was calcium-dependent. In addition, intrasomatic stimulation of the octopaminergic neurons which project to the oviducts resulted in the release of octopamine. The results clearly indicate that both octopamine and proctolin, which have previously been shown to be associated with locust oviducts, are released in a calcium-dependent manner by physiological stimuli. This strengthens the case for octopamine and proctolin as natural regulators of this insect visceral muscle.
D000818:Animals; D002118:Calcium / Q000494:pharmacology; D004558:Electric Stimulation; D005260:Female; D006110:Grasshoppers / Q000378:metabolism* / Q000502:physiology; D009046:Motor Neurons / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D009132:Muscles / Q000187:drug effects / Q000294:innervation* / Q000378:metabolism; D009479:Neuropeptides; D009655:Octopamine / Q000378:metabolism*; D009842:Oligopeptides / Q000378:metabolism*; D010057:Oviducts / Q000294:innervation / Q000378:metabolism; D011188:Potassium / Q000494:pharmacology
D009479:Neuropeptides; D009842:Oligopeptides; D009655:Octopamine; C011536:proctolin; D011188:Potassium; D002118:Calcium