Figure 1.

Effect of “deprivation-induced drinking” (DID) on an “unsaturated” LTP induced by weak tetanic stimulation. Comparison of animals under nondeprived conditions (controls, ▵) and after water deprivation 1 week later (•). Water was provided at different times relative to tetanization. Data are plotted as average change from baseline response (mean ± SEM). Insets display representative analogue traces of a control animal (Left Insets) and a DID subject (Right Insets). For comparison, baseline traces (broken line) are superimposed on recordings taken 15 min (upper traces) and 24 h (lower traces) after weak tetanization. (A) Water access 30 min before tetanization did not affect LTP. Potentiation was sustained for 4 h significantly above baseline (P < 0.05; n = 7). (B) Application of water 5 min prior to tetanization had no influence on the subsequent potentiation (n = 6). (C) DID at the same time as the weak tetanic stimulus markedly reinforced the “unsaturated” LTP, resulting in a potentiation that lasted for more than 24 h (170% ± 11% at 24 h; P < 0.01; n = 7). (D) DID 30 min after tetanization was still effective in protracting an “unsaturated” LTP. The potentiation persisted for at least 24 h (163% ± 12%; P < 0.05; n = 7). (E) DID 1 h after tetanization was unable to reinforce LTP. Potentiation of controls and experimental group showed no difference (n = 6). (F) The potentiation of the slope of the fEPSP was prolonged in a similar way to the potentiation of the PS amplitude (112% ± 4% at 24 h; P < 0.02; n = 7).