The ionic mechanisms concerned in generating the i. p. s. ps of hippocampal pyramidal cells

摘要: A variety of experimental tests has been initiated in order to discover whether the large hyperpolarizing inhibitory postsynaptic potentials (i.p.s.ps) hippocampal pyramidal cells are generated by influx Cl$^{-}$ down a gradient maintained an outward pumping across membrane, as proposed Lux, Llinas and associates for other i.p.s.ps. Intravenous infusion NH$\_{4}$ acetate or intracellular caused little depression extracellular field i.p.s.ps recorded intracellularly, i.e. there was no evidence blockade outwardly directed chloride pump. The recovery time constants seconds from increase chloride, either injections (22.7 $\pm $ 6.9) passage depolarizing current through K$^{+}$ salt-filled microelectrodes (20.6 6.8) did not differ constant depleted electrodes containing salts impermeant anions (21.1 5.4). Depletion concentration following sodium long-lasting shift i.p.s.p. with almost 70 s. These results identical those obtained spinal motoneurons, where very slow explained inward KCl pump triggered low internal K$^{+}$. Our suggest that dependent on does exist neurons at least their somatic membrane. Two alternative hypotheses given account our negative findings respect action rate movements First, original hypothesis Eccles collaborators, which conductance increases both ions produce neurons. However, we have positive involvement ions. Secondly, keeps E$\_{\text{Cl}}$ more than resting potential is solely postulated associates. This located remotely dendrites resistant NH$_{4}$ acetate. would be effective background manner so it interfere appreciably diffusional exchange soma