Release of a Gonad-Stimulating Substance from the Radial Nerves of the Cushion Star,Asterina pectinifera,in response to Excess Potassium*

The release of a gonad-stimulating substance (GSS) from radial nerves stimulated by a K⁺-rich solution was examined in the cushion star, Asterina pectinifera. The threshold concentration of K⁺necessary for the release of a sufficient amount of GSS to induce shedding of mature oocytes from ovarian fragments was 50 to 75 mM. The minimal amount of fresh nerve required for this release was 3 mg per ml of medium. The time of K⁺stimulation necessary to induce maximal GSS release was about 20 min. Repeated stimulations of radial nerves with 100 mM K⁺caused repeated release of GSS.