AU - Mansouri, Farshad Alizadeh AU - Motamedi, Fereshteh AU - Fathollahi, Fereshteh AU - Atapour, Nafiseh AU - Semnanian, Saeed TI - The effects of chronic morphine administration on LTP in hippocampal CA1 area of rat PT - JOURNAL ARTICLE TA - Physiol-Pharmacol JN - Physiol-Pharmacol VO - 1 VI - 1 IP - 1 4099 - http://ppj.phypha.ir/article-1-304-en.html 4100 - http://ppj.phypha.ir/article-1-304-en. SO - Physiol-Pharmacol 1 AB  - The effects of chronic morphine administration on the development of long-term potentiation (LTP) were investigated at the Schaffer collateral-CA1 pyramidal cell synapses of the rat hippocampal slices using primed-bursts tetanic stimulation. Significant enhancement of orthodromic population spike (OPS) was found for all stimulus intensities after tetanic stimulation. OPS enhancement was greatest when tested with low to mid-range stimulus intensities (25, 50 and 100 µA). There was also significant decrease in OPS delay. These responses were similar in slices from both control and morphine dependent rats. At all delivered stimulus intensities, the amount of LTP of OPS in slices from dependent rats was larger than that of control slices. However, these differences in LTP of OPS were significant at low stimulus intensities. These findings suggest that chronic morphine administration had induced changes in CA1 neurocircuitry which modulated synaptic plasticity during high frequency stimulation and appeared as augmented LTP and also inhibition of LTP decay. CP - IRAN IN - 1Department of Physiology, Faculty of Medicine, Shaheed Beheshti University of Medical Sciences, Tehran, I.R.Iran LG - eng PB - Physiol-Pharmacol PG - 45 PT - Experimental research article YR - 1997