Extracellular Ca2+ changes during transmitter application in the leech central nervous system.
Changes in extracellular Ca2+ concentration ([Ca2+]e) evoked by transmitters and transmitter agonists, respectively, and by elevation of bath K+ concentration were recorded in isolated segmental ganglia of the leech Hirudo medicinalis using Ca(2+)-selective microelectrodes. A 1-min bath application of kainate (10 microM), glutamate (1 mM), aspartate (1 mM), or carbachol (200 microM) decreased [Ca2+]e by up to 1 mM, whereas the inhibitory transmitters gamma-amino butyric acid (GABA, 100 microM) and serotonin (5-HT, 100 microM) did not change [Ca2+]e. The amplitude of the kainate-induced changes in [Ca2+]e increased with repetitive applications, and changes were blocked by 6-cyano-7-dinitroquinozaline-2,3-dione (CNQX). Elevation of bath K+ concentration from 4 to 40 mM led to a Ni(2+)-sensitive decrease in [Ca2+]e by 0.9 mM. Our results suggest that excitatory transmission in the leech central nervous system might be accompanied by substantial decreases in [Ca2+]e.
Lohr
C
C
Abteilung für Allgemeine Zoologie, Universität Kaiserslautern, Germany.
Rose
C R
CR
Deitmer
J W
JW
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002217:Carbachol / Q000494:pharmacology; D002490:Central Nervous System / Q000378:metabolism*; D005724:Ganglia / Q000187:drug effects; D018698:Glutamic Acid / Q000494:pharmacology; D007608:Kainic Acid / Q000494:pharmacology; D007865:Leeches; D018377:Neurotransmitter Agents / Q000494:pharmacology*; D011188:Potassium / Q000494:pharmacology
D018377:Neurotransmitter Agents; D018698:Glutamic Acid; D002217:Carbachol; D011188:Potassium; D007608:Kainic Acid; D002118:Calcium