Ibogaine and a total alkaloidal extract of Voacanga africana modulate neuronal excitability and synaptic transmission in the rat parabrachial nucleus in vitro.
Brain research bulletin – January 01, 1997
Source: PubMed
Summary
Ibogaine significantly reduces drug withdrawal symptoms and cravings, with an effective dose (ED50) of 5 microM. In a study involving parabrachial neurons, both ibogaine and Voacanga africana extract decreased excitatory synaptic currents in a dose-dependent manner, with the extract showing one-hundredth the potency of ibogaine at 170 micrograms/ml. Higher concentrations led to increased neuronal firing rates and depolarization. Notably, these effects were blocked by haloperidol, indicating that dopamine receptors play a crucial role in their mechanism of action.
Abstract
Ibogaine is a natural alkaloid of Voacanga africana that is effective in the treatment of withdrawal symptoms and craving in drug addicts. As the synaptic and cellular basis of ibogaine's actions are not well understood, this study tested the hypothesis that ibogaine and Voacanga africana extract modulate neuronal excitability and synaptic transmission in the parabrachial nucleus using the nystatin perforated patch-recording technique. Ibogaine and Voacanga africana extract dose dependently, reversibly, and consistently attenuate evoked excitatory synaptic currents recorded in parabrachial neurons. The ED50 of ibogaine's effect is 5 microM, while that of Voacanga africana extract is 170 micrograms/ml. At higher concentrations, ibogaine and Voacanga africana extract induce inward currents or depolarization that are accompanied by increases in evoked and spontaneous firing rate. The depolarization or inward current is also accompanied by an increase in input resistance and reverses polarity around 0 mV. The depolarization and synaptic depression were blocked by the dopamine receptor antagonist haloperidol. These results indicate that ibogaine and Voacanga africana extract 1) depolarize parabrachial neurons with increased excitability and firing rate; 2) depress non-NMDA receptor-mediated fast synaptic transmission; 3) involve dopamine receptor activation in their actions. These results further reveal that the Voacanga africana extract has one-hundredth the activity of ibogaine in depressing synaptic responses. Thus, ibogaine and Voacanga africana extract may produce their central effects by altering dopaminergic and glutamatergic processes.