Inhibition by 5-hydroxytryptamine and noradrenaline in substantia gelatinosa of guinea-pig spinal trigeminal nucleus.
AUTOR(ES)
Grudt, T J
RESUMO
1. Whole-cell and intracellular recordings were made from neurons in slices of guinea-pig spinal trigeminal nucleus pars caudalis. 2. 5-Hydroxytryptamine (5-HT) hyperpolarized 70% of neurons by activating 5-HT1A receptors. The effect was mimicked by 5-carboxamidotryptamine (5-CT) and (+/-)-2-dipropylamino-8-hydroxy-1,2,3,4-tetrahydronapthalene hydrobromide (8-OH-DPAT) and antagonized by 1-(2-methoxyphenyl)-4-[4-(2-phthalimido)-butyl]-piperazine hydrobromide (NAN 190) and pindobind-5-HT1A. Nine per cent of the neurons were depolarized by 5-HT. 3. In about 20% of recordings, 5-HT also evoked repetitive inhibitory postsynaptic potentials that were mediated by glycine. 4. Noradrenaline (NA) hyperpolarized 71% of neurons. This effect was mediated by activation of alpha 2-adrenoceptors, since 5-bromo-N-(4,5-dihydro-1H-imidazol-2-yl)-6-quinoxalinamine (UK14304) also caused a hyperpolarization and idazoxan (1 microM) blocked the hyperpolarization to both NA and UK14304. Phenylephrine depolarized a subset of neurons and this depolarization was blocked by prazosin, suggesting an action mediated by activation of alpha 1-adrenoceptors. 5. NA also evoked repetitive GABAA-mediated inhibitory postsynaptic potentials in about 20% of recordings. The increase in synaptic activity was mimicked by phenylephrine and blocked by prazosin. 6. These results indicate that there are at least two mechanisms through which 5-HT and NA inhibit neurons: (i) in many cells both 5-HT and NA mediate a hyperpolarization through an increase of a potassium conductance; (ii) 5-HT and NA also activated GABA- and glycine-containing interneurons to cause IPSPs in separate groups of cells.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1157976Documentos Relacionados
- Inhibition of calcium currents by noradrenaline, somatostatin and opioids in guinea-pig submucosal neurones.
- Serotonin and noradrenaline excite GABAergic neurones of the guinea-pig and cat nucleus reticularis thalami.
- Quantal properties of spontaneous EPSCs in neurones of the guinea-pig dorsal lateral geniculate nucleus.
- Endogenous monoamines inhibit glutamate transmission in the spinal trigeminal nucleus of the guinea-pig.
- Inhibitory synaptic potentials in guinea-pig substantia nigra dopamine neurones in vitro.