TY - JOUR
T1 - Sphingosine 1-phosphate enhances spontaneous transmitter release at the frog neuromuscular junction
AU - Brailoiu, Eugen
AU - Cooper, Robin L.
AU - Dun, Nae J.
PY - 2002/8
Y1 - 2002/8
N2 - Intracellular recordings were made from isolated frog sciatic-sartorius nerve-muscle preparations, and the effects of sphingosine 1-phosphate (S1-P) on miniature endplate potentials (MEPPs) were studied. Extracellular application of S1-P (1 and 30 μM) had no significant effects on the frequency and amplitude of MEPPs. Delivery into nerve terminals by liposomes containing 10-5, 10-4 or 10-3 M S1-P was associated with a concentration-dependent increase in MEPP frequency of 37, 63 and 86%. The per cent of median MEPP amplitude was not significantly changed, but there was an increase in the number of 'giant' MEPPs. Pre-exposure of the preparations to S1-P 10-5 but not 10-8 M entrapped in liposomes for 15 min blocked the effects of subsequent superfusion of S1-P (10-4 M)-filled liposomes on MEPP frequency. Thus, intracellular S1-P receptors seem to undergo 'desensitization' to higher concentrations of S1-P. The result provides the first evidence that S1-P acting intracellularly but not extracellularly enhances spontaneous transmitter release at the frog neuromuscular junction.
AB - Intracellular recordings were made from isolated frog sciatic-sartorius nerve-muscle preparations, and the effects of sphingosine 1-phosphate (S1-P) on miniature endplate potentials (MEPPs) were studied. Extracellular application of S1-P (1 and 30 μM) had no significant effects on the frequency and amplitude of MEPPs. Delivery into nerve terminals by liposomes containing 10-5, 10-4 or 10-3 M S1-P was associated with a concentration-dependent increase in MEPP frequency of 37, 63 and 86%. The per cent of median MEPP amplitude was not significantly changed, but there was an increase in the number of 'giant' MEPPs. Pre-exposure of the preparations to S1-P 10-5 but not 10-8 M entrapped in liposomes for 15 min blocked the effects of subsequent superfusion of S1-P (10-4 M)-filled liposomes on MEPP frequency. Thus, intracellular S1-P receptors seem to undergo 'desensitization' to higher concentrations of S1-P. The result provides the first evidence that S1-P acting intracellularly but not extracellularly enhances spontaneous transmitter release at the frog neuromuscular junction.
KW - Cyclic ADP ribose
KW - IP3
KW - Miniature endplate potentials
KW - Nicotinic acid adenine dinucleotide phosphate
KW - Sphingosine 1-phosphate
UR - http://www.scopus.com/inward/record.url?scp=0036687577&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0036687577&partnerID=8YFLogxK
U2 - 10.1038/sj.bjp.0704839
DO - 10.1038/sj.bjp.0704839
M3 - Article
C2 - 12163341
AN - SCOPUS:0036687577
SN - 0007-1188
VL - 136
SP - 1093
EP - 1097
JO - British Journal of Pharmacology
JF - British Journal of Pharmacology
IS - 8
ER -