Proceedings of The Physiological Society
University of Cambridge (2008) Proc Physiol Soc 11, C116
The long term potentiation in amygdalar BLA-CE pathway from MMP-9 overexpressed rats
T. M. Górkiewicz1,2, M. Wawrzyniak1, M. Balcerzyk1, V. Lioudyno1, P. Michaluk1, M. Gawlak1, L. Kaczmarek1
1. Department of Molecular and Cellular Neurobiology, The Nencki Institute of Experimental Biology, Warsaw, Poland. 2. Department of Biophysics, Warsaw University of Life Sciences, Warsaw, Poland.
Matrix metalloproteinase-9 (MMP-9) acts ectracellularly to cleave components of extracellular matrix (Michaluk and Kaczmarek, 2007). MMP-9 is expressed in the brain, where it is produced especially by neurons. MMP-9 is crucial for remodeling of extracellular environment, essential for synaptic plasticity, learning and memory. The amygdala is a heterogenous brain structure important for regulation of emotional aspects of memory as well as autonomic and endocrine responses. It has been shown that the central nucleus (CE) of amygdala is involved in appetitive learning (Knapska et al., 2006). In the present study, we investigated the importance of MMP-9 in synaptic plasticity in the CE. MMP levels were analyzed by zymography and MMP-9 function was assessed by employing long term potentiation (LTP) model of synaptic plasticity. We studied slices obtained from the transgenic rats with neuron-specific MMP-9 overexpression driven by Synapsin I promoter (Wilczynski et al., 2008). The basolateral nucleus of amygdala (BLA) was teta burst stimulated using a bipolar electrode and EPSPs were colected from CE. At 15 min. after achieving a stable baseline recording, theta-burst stimulation (TBS, three trains of high frequency stimuli applied every 5 min) protocol was used to evoke LTP that was recorded for the next 90 min. In both, MMP-9-overexpressing and control group, LTP persisted throughout the experiment. However, the level of LTP obtained in slices from MMP-9 overexpressing rats (6 slices from 4 animals) was lower than from the control ones (5 slices from 3 rats) by 50%± 3,19% (p=0.015, ANOVA for repeated measures) and this effect was maintained throughout all the 90 min of recording. The present observation suggests that the proper level of MMP-9 expresion and activity is essential for synaptic plasticity in the BLA-CE pathway, whereas MMP-9 overexpresion may cause destabilization of neuronal environment and decreased activity-dependent strengthening of synaptic transmission.
Where applicable, experiments conform with Society ethical requirements