Effects of aldrin-transdiol on neuromuscular facilitation and depression.
The effects of aldrin-transdiol, one of the active metabolites of the insecticide dieldrin, on evoked transmitter release, neuromuscular facilitation and neuromuscular depression have been studied in frog sartorius nerve-muscle preparations. Conventional techniques of intracellular recordings were used. Aldrin-transdiol caused a marked increase in end-plate potential amplitude under conditions of low quantal content, i.e., in Mg2+-blocked junctions. The increase in end-plate potential amplitude was less pronounced in curarized junctions, in which the transmitter release was not impaired. Concomitant with the increase in end-plate potential size there was a marked enhancement of facilitation during short trains of stimuli applied to the motor nerve. The decay of facilitation was, however, not seriously affected by aldrin-transdiol. These effects may be explained in terms of the known 'calcium hypothesis' by assuring that aldrin-transdiol increases the amount of calcium which enters the nerve terminal during the nerve impulse. The increase in end-plate potential amplitude and in facilitation by aldrin-transdiol was transient. At later stages of poisoning, end-plate potential and facilitation decreased below control level and neuromuscular depression was significantly enhanced. This latter effect may be the result of a direct inhibitory effect of aldrin-transdiol on transmitter mobilization. As far as the fall in end-plate potential amplitude is concerned the known suppressive action of aldrin-transdiol on the chemical sensitivity of the postsynaptic membrane and on the nerve action potential probably plays a part as well. Finally, neuromuscular transmission was completely blocked by aldrin-transdiol.
D000452:Aldrin / Q000031:analogs & derivatives* / Q000494:pharmacology; D000818:Animals; D003864:Depression, Chemical; D004558:Electric Stimulation; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects; D009045:Motor Endplate / Q000187:drug effects; D009469:Neuromuscular Junction / Q000187:drug effects* / Q000502:physiology; D018377:Neurotransmitter Agents / Q000378:metabolism; D011893:Rana esculenta; D011896:Rana temporaria; D013268:Stimulation, Chemical; D009435:Synaptic Transmission / Q000187:drug effects; D014403:Tubocurarine / Q000494:pharmacology
D018377:Neurotransmitter Agents; C006448:aldrin-transdiol; D000452:Aldrin; D014403:Tubocurarine