Figure 6

Possible mechanism of presynaptic inhibition in primary afferent terminals by GABA. Bath application of bicuculline (Bic) and/or picrotoxin (Pic) increases presynaptic excitation by blocking GABA receptors (GABA-R) on afferent terminals. MFA blocks the GABAergic action partially, inhibiting glial cells and leaving the neuronal path intact. Blocking glutamate receptors with D-AP5 and CNQX potentiates the presynaptic excitation by inhibiting the activity of GABAergic neurons and the presynaptic glutaminergic action. Further addition of MFA together with D-AP5 and CNQX removes all the inhibitory actions to the presynaptic terminals.