The commissure of Probst as a source of GABAergic inhibition

Whole-cell patch-clamp recordings were made from neurons in the rat's dorsa l nucleus of the lateral lemniscus (DNLL) in a brain slice preparation. Pla nes of section were chosen to preserve the integrity of fibers in the commi ssure of Probst (CP) and postsynaptic responses were evoked by electrical s timulation along its length. Results showed that the crossed projection to the DNLL through the CP is mainly, if not exclusively, inhibitory in the ra t. Inhibitory postsynaptic responses (IPSPs) evoked by stimulation of the C P were blocked by the gamma-aminobutyric acid (GABA)A receptor antagonist b icuculline, but were unaffected by the glycine receptor antagonist strychni ne, supporting the conclusion that the crossed inhibitory projection to DNL L from the contralateral DNLL is GABAergic. Stimulation of the CP close to the DNLL frequently evoked excitatory postsynaptic responses as well as IPS Ps, but stimulation near the midline evoked IPSPs only. Thus, the excitator y responses probably originated from a pathway other than the projection to the DNLL from the contralateral DNLL through the CP. (C) 1999 Elsevier Sci ence B.V. All rights reserved.