title: On the action of ruthenium red and neuraminidase at the frog neuromuscular junction.
abstract: 1. The actions of the polyvalent cationic dye Ruthenium Red and the enzyme neuraminidase were studied at the frog neuromuscular junction. 2. Both Ruthenium Red (0.5-40 microM) and neuraminidase (1, 2 and 4 u.) reduced the miniature end-plate potential (m.e.p.p.) amplitude irreversibly with little change in frequency. This effect could be attributed to the depressant action of these agents on the amplitude of extracellularly recorded miniature end-plate currents (m.e.p.c.s) coupled with their shortening effect on the duration of these m.e.p.c.s. For example, 10 microM-Ruthenium Red reduced the time constant of decay (tau D) of extracellular m.e.p.c.s to 35% of the control value. 3. Ruthenium Red (5, 10 and 15 microM) produced a pronounced reduction in the post-synaptic end-plate sensitivity to microiontophoretically applied acetylcholine. In some cases this effect was fully reversible on wash-out of the dye. 4. Amplitude histograms of m.e.p.c.s recorded under voltage clamp showed a similar shift of the modal value to lower levels in the presence of Ruthenium Red. Over the voltage range -70 to -110 mV the action of Ruthenium Red on the tau D was not voltage dependent. 5. The actions of Ruthenium Red on tau D were not affected by anaesthetic agents, such as the short-chain alcohols which increased tau D, or ketamine which decreased tau D. 6. Some possible modes of action of Ruthenium Red and neuraminidase are briefly discussed.
mesh_terms: D000200:Action Potentials / Q000187:drug effects; D000777:Anesthetics / Q000494:pharmacology; D000818:Animals; D003864:Depression, Chemical; D005260:Female; D066298:In Vitro Techniques; D008297:Male; D009045:Motor Endplate / Q000502:physiology; D009439:Neuraminidase / Q000494:pharmacology*; D009469:Neuromuscular Junction / Q000187:drug effects*; D011894:Rana pipiens; D011896:Rana temporaria; D012428:Ruthenium / Q000494:pharmacology*; D012430:Ruthenium Red / Q000494:pharmacology*; D013997:Time Factors
chemical_list: D000777:Anesthetics; D012430:Ruthenium Red; D012428:Ruthenium; D009439:Neuraminidase