Neuromuscular transmission in a primitive insect: modulation by octopamine, and catch-like tension.
The third pair of legs of the primitive New Zealand orthopteran insect, the " weta ", has and innervation and muscle cell distribution exactly similar to that of locusts, but wetas do not jump. Neuromuscular transmission to the slow excitatory axon ( SETi ) is potentiated more than 10-fold by the natural modulator octopamine (OCT). A brief burst of SETi impulses following infusion of as little as 10(-8) M OCT is followed by a very long-lasting plateau of catch-like tension (CT). The plateau is abruptly relaxed by a single inhibitory impulse, or even by a single SETi impulse if this arrives no sooner than about 30 sec following excitation. CT is used by wetas in a defense posture. Locusts and grasshoppers have a different type of modulation by OCT.
D000818:Animals; D008564:Membrane Potentials; D009119:Muscle Contraction / Q000187:drug effects; D009469:Neuromuscular Junction / Q000502:physiology*; D009655:Octopamine / Q000494:pharmacology*; D009987:Orthoptera / Q000502:physiology*; D009435:Synaptic Transmission / Q000187:drug effects*
D009655:Octopamine