C. Lohr et al., EXTRACELLULAR CA2-NERVOUS-SYSTEM( CHANGES DURING TRANSMITTER APPLICATION IN THE LEECH CENTRAL), Neuroscience letters, 205(1), 1996, pp. 57-60
Changes in extracellular Ca2+ concentration ([Ca2+](e)) evoked by tran
smitters and transmitter agonists, respectively, and by elevation of b
ath K+ concentration were recorded in isolated segmental ganglia of th
e leech Hirudo medicinalis using Ca2+-selective microelectrodes. A 1-m
in bath application of kainate (10 mu M), glutamate (1 mM), aspartate
(1 mM), or carbachol (200 mu M) decreased [Ca2+](e) by up to 1 mM, whe
reas the inhibitory transmitters gamma-amino butyric acid (GABA, 100 m
u M) and serotonin (5-HT, 100 mu M) did not change [Ca2+](e). The ampl
itude of the kainate-induced changes in [Ca2+](e) increased with repet
itive applications, and changes were blocked by 6-cyano-7-dinitroquino
zaline-2,3-dione (CNQX). Elevation of bath K+ concentration from 4 to
40 mM led to a Ni2+-sensitive decrease in [Ca2+](e) by 0.9 mM. Our res
ults suggest that excitatory transmission in the leech central nervous
system might be accompanied by substantial decreases in [Ca2+](e).