The Effects of Sodium, Potassium and Calcium on Metabolism of Rat’s Cerebral Cortical Slice With or Without Electrical Stimulation

Effects of 2, 4-Dinitrophenol and Ouavain on Respiration and Metabolism of Separated Cerebral Cortex in Both Presence and Absence of Electrical Stimulation

“…In the present experiment , these effects were also induced in the cerebral tis sue with DNP in the absence of external sodium; this fact was almost analogous to the effect of a further removal of calcium from the sodium-free medium (2) . It has been observed that with 5 x 10-5M-DNP which doubled oxygen uptake of the cerebral tissue , the non inulin K of the cerebral tissue fell and Na rose very rapidly (7) ; in frog skins , DNP decreased its electrical conductance and caused a marked decrease of active Na transport , whereas the passive Na transport remained unchanged or was slightly decreased (8) .…”

“…uptake and metabolism of the unstimulated tissue, while the effects of electrical stimulation appeared to have been con siderably depressed in this case (Expt . 2d) ; that is, it seems as if DNP in 1 x 10--' M simulated the effects of high external potassium (about 50 mm) under the presence of external sodium, as already reported in the previous paper (2). 1 Ouabain : G-strophanthin is dissolved in normal medium, and tipped in from the side chamber as usual.…”

“…The lack of sodium in the medium always shown the lowest levels of respira tion and metabolism of cerebral cortical slices, and also almost the similar level in either the presence or absence of electrical stimulation; accordingly, the removal of external so dium did not allow the tissue to respond to electrical stimulation (Expt. 2a, in Table 2) ; the detailed description concerning this has been made formerly (2) DNP: In the present experiment, about 3 minutes before the preincubation period ended, DNP dissolved in normal medium was added from the side chamber to the main compartment so as to obtain the corresponding final concentration. Table 2 shows the re sults concerning DNP.…”

“…The various methods and procedures employed in this experiment have been the same as described in detail in the previous paper (2). We obtained six or four groups of tissue slices from the same rat's cerbral cortex by employing a somewhat particular pro cedure of slicing.…”

“…The fact that separated mammalian cerebral cortical tissues , suitably maintained in vitro, show remarkable respiratory and metabolic responses to adequate electrical stimu lation has already been published frequently (1) ; recently it was shown that such respira tory and metabolic responses to adequate electrical stimulation were dependent only on the concentration of external sodium, approximately in Michaelis Menten fashion , but potas sium by itself was inert to this metabolism , and calcium was independent of such responses (2). Meanwhile, a number of studies are being made everywhere at present in order to elucidate the exact mechanism of linkage between active cation transport and metabolism .…”