A putative met-enkephalin releaser, kyotorphin enhances intracellular Ca2+ in the synaptosomes.
Kyotorphin (Tyr-Arg) at 1 to 100 microM increased the intracellular [Ca2+]i, determined with Quin-II in the slice and the entry of 45Ca2+ entry into synaptosomes of the lower brain stem of the rat. These effects were not antagonized by nifedipine nor verapamil. However, since this dipeptide caused no changes on the membrane potentials of the synaptosomes, measured with Rhodamine 6G, it is suggested that the kyotorphin-induced increase in the [Ca2+]i may be due not to effects on the voltage dependent Ca2+ channels and Na+-Ca2+ exchange mechanisms caused by the changes of the membrane potentials, but to the specific receptor (kyotorphin receptor)-mediated mechanisms.
D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D001933:Brain Stem / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D004723:Endorphins / Q000494:pharmacology*; D004744:Enkephalin, Methionine / Q000378:metabolism*; D007473:Ion Channels / Q000187:drug effects; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D051381:Rats; D011919:Rats, Inbred Strains; D013574:Synaptosomes / Q000187:drug effects / Q000378:metabolism*
D004723:Endorphins; D007473:Ion Channels; C019448:kyotorphin; D004744:Enkephalin, Methionine; D002118:Calcium