GABAB receptor-mediated responses in GABAergic projection neurones of rat nucleus reticularis thalami in vitro.
AUTOR(ES)
Ulrich, D
RESUMO
1. Whole-cell voltage-clamp recordings were obtained from GABAergic neurones of rat nucleus reticularis thalami (NRT) in vitro to assess pre- and postsynaptic GABAB receptor-mediated responses. Presynaptic inhibition of GABA release was studied at terminals on local axon collaterals within NRT as well as on projection fibres in the somatosensory relay nuclei. 2. The GABAB receptor agonist (R)-baclofen (10 microM) reduced monosynaptically evoked GABAA-mediated inhibitory postsynaptic currents (IPSCs) in NRT and somatosensory relay cells to 11 and 12% of control, respectively. 3. Action potential-independent miniature IPSCs (mIPSCs) were observed in both cell types. Mean mIPSC amplitude was 20 pA in both NRT and relay cells at a holding potential of 0 mV. The mean mIPSC frequencies were 0.83 and 2.2 Hz in NRT and relay cells, respectively. Baclofen decreased mIPSP frequency by about half in each cell type without affecting amplitude. 4. Paired-burst inhibition of evoked IPSCs was studied in relay and NRT cells by applying pairs of 100 Hz stimulus bursts separated by 600 ms. The mean ratio of second to first peak IPSC amplitudes was 0.77. 5. In NRT cells baclofen induced a linear postsynaptic conductance increase of 0.82 nS with an associated reversal potential of -121 mV. A small (0.14 nS) GABAB component of the evoked IPSC was detected in only a minority of NRT cells (3 of 18). 6. All pre- and postsynaptic effects of baclofen, as well as PBI, were largely reversed by the specific GABAB receptor antagonist CGP 35348 (0.5 mM). 7. We conclude that activation of GABAB receptors in NRT leads to presynaptic autoinhibition of IPSCs in both NRT and relay cells, and to direct activation of a small linear K+ conductance. In addition our experiments suggest that reciprocal connectivity within NRT can be partially mediated by a small GABAB inhibitory event.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1159030Documentos Relacionados
- NMDA receptor-mediated rhythmic bursting activity in rat supraoptic nucleus neurones in vitro.
- Intrinsic properties of nucleus reticularis thalami neurones of the rat studied in vitro.
- Angiotensin II enhances GABAB receptor-mediated responses and expression in nucleus tractus solitarii of rats
- GABAB receptor-mediated inhibition of Ca2+ currents and synaptic transmission in cultured rat hippocampal neurones.
- Serotonin and noradrenaline excite GABAergic neurones of the guinea-pig and cat nucleus reticularis thalami.