Effect of Pentylenetetrazol (PTZ) as a Convulsant Drug, on the Ionic Current of D5 Neuronal Soma Membrane in Helix Aspersa: Using Intracellular Recording Technique (Voltage Clamp)

Pentylenetetrazol (PTZ) is one of the most often used epileptogenic agents. Several effects of this epileptogenic drug have been described, but the mechanism of the epileptogenic action of PTZ at the cellular level is still unclear. In this study the effect of PTZ, on the ionic currents of D5 neuronal soma membrane in Helixaspersa, using intracellular recording technique was investigated. Experiments were carried out on D5 neuronal soma membrane located in the left parietal ganglion of the snail, Helix aspersa. The properties of the inward and outward cationic currents induced by PTZ (25 mM) were analyzed using two electrodes voltage clamp technique. The extracellular application of PTZ (25 mM), caused an increase in spontaneous firing activity and with 4 to 7 minutes after adding PTZ, led to a dramatic changes in action potential shape of D5 neuronal cells. Under voltage clamp condition, the peak amplitude of inward current in the presence of PTZ reduced 16.5 % within 7 min. The current-voltage relationship of inward current also shifted by 23.18 % in a hyperpolarizing direction. Furthermore, the peak amplitude of outward currents showed a reduction of about 6.75%. The results of this study show that PTZ by effecting on the properties of bioelectrical activity causes an increase in the excitability of D5 cells. In addition, the effect of PTZ on inward and outward currents accounts for an induction of epileptic activity.