Extra- and intracellular XXXX promote spontaneous transmitter release from frog motor nerve endings.

@entity9421 @entity2426 @entity4993 @entity3733 @entity51375 @entity4291
Similar to @entity51375 , @entity4291 breakdown generates several lipids, including @entity4993 (SPC), that are putative signaling molecules. The present study was undertaken to evaluate the involvement of SPC in transmitter release process. Intracellular recordings were made from isolated frog sciatic-sartorius nerve-muscle preparations, and the effects of SPC on neurosecretion in the form of miniature endplate potentials (MEPPs) were assessed. Extracellular application of SPC mixture (D,L-SPC) at 1, 10, and 25 microM increased the MEPP frequency by 68, 96, and 127%, respectively. D-erythro-SPC (dissolved in @entity3733 but not coupled to bovine serum albumin), but not L-threo-SPC, was active extracellular; the former (at 10 microM) increased the MEPP frequency by 143%. D-erythro-SPC treatment did not significantly change the median amplitude or frequency-distribution of MEPPs. Intracellular delivery via liposomes, in which 10, 100, or 1000 microM SPC mixture was entrapped in liposomal aqueous phase, induced a concentration-dependent increase in MEPP frequency of 45, 91, and 100%, respectively. D-erythro-SPC and L-threo-SPC at the concentration of 100 microM increased the MEPP frequency by 117 and 67%, respectively, or 91 and 61%, respectively, when coupled to bovine serum albumin. Pretreatment with @entity2426 significantly reduced but did not abolish the effects of extracellular D-erythro-SPC (10 microM) or liposomes containing 100 microM D-erythro-SPC. Liposomes filled with 100 microM @entity9421 (IP3) enhanced the MEPP frequency to the same magnitude as 100 microM D-erythro-SPC entrapped in liposomes. However, administration of 100 microM D-erythro-SPC and IP3 entrapped in the same liposomes enhanced the MEPP frequency by 70%, which was less than that produced by these two compounds alone. The result provides the first electrophysiological evidence that SPC can modulate transmitter release by an extra- or intracellular action at the frog motor nerve ending.
