A-type K+ current dominates somatic excitability of delayed firing neurons in rat substantia gelatinosa.
Synapse
; 65(7): 601-7, 2011 Jul.
Article
en En
| MEDLINE
| ID: mdl-21484879
ABSTRACT
Substantia gelatinosa neurons display three main types of intrinsic firing behavior tonic, adapting, and delayed onset. Here, voltage-gated currents expressed by delayed firing neurons were studied in nucleated patches obtained in spinal cord slices of 3-5 weeks-old rats. Inward Na+ current was negligible under these conditions and was usually occluded by superposition of much larger outward currents. Two kinds of outward currents were found, an A-type (K(A) ) and delayed rectifier (K(DR) ) potassium currents. K(A) activated rapidly (<1.5 ms at >-20 mV) and operated at subthreshold membrane potentials; voltages of steady-state half-maximal activation and inactivation were -38.7 and -87.2 mV, respectively. Inactivation was biexponential with a dominant fast component (~90%, time constant â¼8 ms). K(DR) activated more slowly (<8 ms at >-20 mV), half-maximal activation was -23.6 mV, and decayed mono-exponentially with a time constant 70-110 ms. Maximal amplitudes of K(A) were almost 10-times larger than those of K(DR) , their respective densities were 8.5 and 0.97 µS µm⻲. Tetraethylammonium, 5 mM, blocked K(DR) but not K(A) , whereas both currents were depressed by 5 mM 4-aminopyridine. In current-clamp recordings, 4-action potential but not tetraethylammonium abolished firing delay suggesting the causative role of K(A) . Thus, the predominance of fast K(A) over other somatic currents is a distinctive feature of delayed firing neurons among all other types of substantia gelatinosa neurons and likely explains the appearance of their typical firing delay.
Texto completo:
1
Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Sustancia Gelatinosa
/
Canales de Potasio
/
Potenciales de la Membrana
/
Neuronas
Límite:
Animals
Idioma:
En
Revista:
Synapse
Asunto de la revista:
NEUROLOGIA
Año:
2011
Tipo del documento:
Article
País de afiliación:
Ucrania