Depolarization of rat locus coeruleus neurons by adenosine 5'-triphosphate
| Autor: | L. Harms, M. Tschöpl, E.P. Finta, Peter Illes |
|---|---|
| Rok vydání: | 1992 |
| Předmět: |
Male
Tetrodotoxin In Vitro Techniques Inhibitory postsynaptic potential Membrane Potentials chemistry.chemical_compound Slice preparation Adenosine Triphosphate Animals Magnesium Evoked Potentials Membrane potential Neurons Tetraethylammonium Chemistry General Neuroscience Sodium channel Sodium Depolarization Afterhyperpolarization Rats Inbred Strains Rats Xanthines Biophysics Locus coeruleus Calcium Locus Coeruleus Neuroscience |
| Zdroj: | Neuroscience. 48(4) |
| ISSN: | 0306-4522 |
| Popis: | Intracellular recordings were performed in a pontine slice preparation of the rat brain containing the locus coeruleus. The enzymatically stable P2-purinoceptor agonist alpha,beta-methylene ATP increased the firing rate without altering the amplitude or shape of action potentials; the afterhyperpolarization following a spike was not changed either. When locus coeruleus neurons were hyperpolarized by current injection in order to prevent spontaneous firing, alpha,beta-methylene ATP produced depolarization and a slight increase in the apparent input resistance. A combined application of kynurenic acid and bicuculline methiodide failed to alter the alpha,beta-methylene ATP-induced depolarization, and tetrodotoxin only slightly depressed it. A gradual shift of the membrane potential by hyperpolarizing current injection led to a corresponding decrease, but no abolition or reversal of the alpha,beta-methylene ATP effect. In the hyperpolarized region, the current-voltage curve of alpha,beta-methylene ATP came into close approximation with, but did not cross, the control curve. Elevation of the external K+ concentration, or the intracellular application of Cs+ by diffusion from the microelectrode, depressed the response to alpha,beta-methylene ATP; external tetraethylammonium was also inhibitory. External Ba2+ and Cs+ had no effect or only slightly decreased the alpha,beta-methylene ATP-induced depolarization. A low Na+, or a low Ca2+ high Mg2+ medium, as well as the presence of Co2+ in the medium, markedly reduced or even abolished the depolarization by alpha,beta-methylene ATP. ATP itself did not produce consistent changes in the membrane potential or input resistance. However, in the presence of the P1-purinoceptor antagonist 8-cyclopentyl-1,3-dipropylxanthine, ATP consistently increased the firing rate and evoked an inward current. In conclusion, P2-purinoceptor activation appears to depolarize locus coeruleus neurons by inhibiting a persistent potassium current, and at the same time opening calcium-sensitive sodium channels or calcium-sensitive non-selective cationic channels. |
| Databáze: | OpenAIRE |
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