Effects of monensin on the response to low potassium in a molluscan muscle, the radular protractor of Busycon canaliculatum.
1. A sucrose gap technique was used to study the effect of a sodium ionophore on the potential changes which occur during superfusion with potassium-free solution. Crucial values were checked with a microelectrode technique. 2. Potassium-free solution induces a complex response consisting of a hyperpolarizing phase (HP) and then a depolarization phase (DP) during exposure to zero K+, followed by a transient extra hyperpolarizing phase (EHP) on readmission of K+. 3. The sodium ionophore, monensin, has the effect of increasing the amplitude of the DP, in perfusion medium of normal Na+ content. This is similar to the effect of treatment with neurohumors and to the after-effect of direct electrical stimulation. The effects of ACh and monensin are additive. 5. These effects are consistent with an action of monensin in increasing Na+ flux in the direction of the concentration gradient and support the hypothesis that neurohumors stimulate the sodium pump by increasing Na+ influx.
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D004558:Electric Stimulation; D005663:Furans / Q000494:pharmacology*; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects; D008974:Mollusca / Q000187:drug effects*; D008985:Monensin / Q000494:pharmacology*; D009132:Muscles / Q000187:drug effects*; D011188:Potassium / Q000494:pharmacology*; D012701:Serotonin / Q000494:pharmacology; D013327:Strophanthidin / Q000494:pharmacology
D005663:Furans; D012701:Serotonin; D013327:Strophanthidin; D008985:Monensin; D000109:Acetylcholine; D011188:Potassium