[Mechanisms of synaptic transmission in the ampullae of Lorenzini in skates]

Effects of Mg2+, L-glutamate (L-GLU) and L-glutamic acid diethyl ester (GDEE) on background and evoked activity of the ampullae of Lorenzini were studied in marine skates (Raja clavata). Perfusion of the basal membrane with 10(-4)-10(-5) M L-GLU produced significant and reversible changes in background firing rate depending on its initial level. When excitability was blocked by perfusion with Mg2+, the background activity could be restored in L-GLU (10(-4)-10(-5) M) Mg2+-containing solution. GDEE (10(-3)-10(-4) M) blocked the synaptic transmission. The results are consistent with the view that L-GLU is the synaptic transmitter in the ampullae of Lorenzini of the skate.