The rat gracile nucleus in vitro: I. Evidence for a GABA-mediated depolarisation of the dorsal column afferents.
The preparation and maintenance of a novel slice of the rat gracile nucleus is described. The slice includes both gracile nuclei as well as an intact afferent input from the dorsal columns. Extracellular recording revealed that a compound tract action potential (CAP) could be recorded from the gracile nucleus following stimulation of the ipsilateral dorsal column. The CAP was followed by slower field potentials which are thought to be dependent on synaptic activity. Four consequences of stimulating the dorsal columns were observed: (1) a subsequent CAP was conducted more rapidly along the afferents whether it travelled in an orthodromic or antidromic direction; (2) the amplitude of a subsequent orthodromic CAP was reduced; (3) the amplitude of a subsequent submaximal antidromic CAP was increased; and (4) a slow positive potential could be recorded from the dorsal columns. All 4 phenomena had comparable time-courses and were similarly sensitive to agents which reduce synaptic transmission. Pharmacological evidence indicated that all 4 phenomena were mediated by GABA. It is suggested that a GABA-mediated depolarization of the gracile afferents can be evoked in this slice.
D000344:Afferent Pathways / Q000502:physiology; D000818:Animals; D001931:Brain Mapping; D005071:Evoked Potentials; D005260:Female; D066298:In Vitro Techniques; D007473:Ion Channels / Q000502:physiology; D008297:Male; D008526:Medulla Oblongata / Q000502:physiology*; D009413:Nerve Fibers, Myelinated / Q000502:physiology; D051381:Rats; D011930:Reaction Time / Q000502:physiology; D013569:Synapses / Q000502:physiology; D009435:Synaptic Transmission; D005680:gamma-Aminobutyric Acid / Q000502:physiology*
D007473:Ion Channels; D005680:gamma-Aminobutyric Acid