The effects of Al+3 and Pb+2 were examined on the calcium spikes of Helix aspersa F77
neuron, using two microelectrode current clamp technique. These results show that in
the normal Ringer, the action potential is sodium-calcium dependent. The important
role of calcium ions in the depolarizing phase of the action potential was observable as
long duration action potentials with a plateau, when Na + and K+ ions were eliminated
and sodium-potassium channel blockers were used. Nifedipine (lµ,M), a specific L-type
calcium channel blaker, decreased action potential duration (P < 0.01). Application of
lead (0.6 and 3 µ,M) led to significant decrease in threshold and duration of action
potential (P<0.05). The effects of lead were not dose dependent. Aluminum (150µM)
at pH between 6.8 to 6.9, affected excitability and bioelectrical characteristics of F77
neurons. The resting membrane potential, firing threshold, peak, amplitude, duration
and frequency of action potentials were reduced significantly in the presence of
aluminium.
In summary, the results of this study demonstrate that lead and aluminum exert at
least a part of their neurotoxic actions by alterning the neuronal excitability and action
potential characteristics.