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Matrix metalloproteinase 9 (MMP-9) is indispensable for long term potentiation in the central and basal but not in the lateral nucleus of the amygdala.

Gorkiewicz T, Balcerzyk M, Kaczmarek L, Knapska E - Front Cell Neurosci (2015)

Bottom Line: In the present study we show that LTP in the basal and central but not lateral amygdala (LA) is affected by MMP-9 knock-out.The MMP-9 dependency of LTP was confirmed in brain slices treated with a specific MMP-9 inhibitor.The results suggest that MMP-9 plays different roles in synaptic plasticity in different nuclei of the amygdala.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurophysiology, Nencki Institute of Experimental Biology, Polish Academy of Sciences Warszawa, Poland ; Department of Biophysics, Warsaw University of Life Sciences Warszawa, Poland.

ABSTRACT
It has been shown that matrix metalloproteinase 9 (MMP-9) is required for synaptic plasticity, learning and memory. In particular, MMP-9 involvement in long-term potentiation (LTP, the model of synaptic plasticity) in the hippocampus and prefrontal cortex has previously been demonstrated. Recent data suggest the role of MMP-9 in amygdala-dependent learning and memory. Nothing is known, however, about its physiological correlates in the specific pathways in the amygdala. In the present study we show that LTP in the basal and central but not lateral amygdala (LA) is affected by MMP-9 knock-out. The MMP-9 dependency of LTP was confirmed in brain slices treated with a specific MMP-9 inhibitor. The results suggest that MMP-9 plays different roles in synaptic plasticity in different nuclei of the amygdala.

No MeSH data available.


Genetic inhibition of MMP-9 results in destabilization of LTP in the central and basal but not in the lateral amygdala. (A) fEPSP in the EC–LA amygdala pathway was similar in slices from mice lacking functional MMP-9 gene (MMP-9 KO, open circles n = 6) and control animals (WT, filled circles, n = 5). (B) fEPSP evoked in the LA-BA pathway in slices from MMP-9 KO mice (open circles, n = 7) within first 70 min had the same magnitude as LTP in slices from control animals (WT, filled circles, n = 7); however afterwards it went down to the baseline level. (C) fEPSP induced in the BA-CeAm pathway in slices from MMP-9 KO mice (open circles, n = 7) had the same amplitude as LTP evoked in control slices (filled circles, n = 7) within first 30 min after induction. Then, LTP in MMP-9 KO slices gradually decreased to the baseline level. Left panels show graphs with time course of maximal EPSP amplitudes normalized to baseline. Black arrows mark the time of application of TBS stimulation. Error bars represent SEM. Middle panels show exemplary traces of fEPSP recorded 10 min before (black) and 15 and 90 min after (gray) induction of LTP. Scale bars = 0.2 mV and 5 ms. Right panels present photographs of mouse amygdala (Nissl staining) with positions of stimulating (red arrow) and recording (black arrow) electrodes.
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Figure 1: Genetic inhibition of MMP-9 results in destabilization of LTP in the central and basal but not in the lateral amygdala. (A) fEPSP in the EC–LA amygdala pathway was similar in slices from mice lacking functional MMP-9 gene (MMP-9 KO, open circles n = 6) and control animals (WT, filled circles, n = 5). (B) fEPSP evoked in the LA-BA pathway in slices from MMP-9 KO mice (open circles, n = 7) within first 70 min had the same magnitude as LTP in slices from control animals (WT, filled circles, n = 7); however afterwards it went down to the baseline level. (C) fEPSP induced in the BA-CeAm pathway in slices from MMP-9 KO mice (open circles, n = 7) had the same amplitude as LTP evoked in control slices (filled circles, n = 7) within first 30 min after induction. Then, LTP in MMP-9 KO slices gradually decreased to the baseline level. Left panels show graphs with time course of maximal EPSP amplitudes normalized to baseline. Black arrows mark the time of application of TBS stimulation. Error bars represent SEM. Middle panels show exemplary traces of fEPSP recorded 10 min before (black) and 15 and 90 min after (gray) induction of LTP. Scale bars = 0.2 mV and 5 ms. Right panels present photographs of mouse amygdala (Nissl staining) with positions of stimulating (red arrow) and recording (black arrow) electrodes.

Mentions: MMP-9 homozygous knock-out mice on a C57BL/6 background were obtained from Dr. Z. Werb (University of California, San Francisco). These mice were bred with C57BL/6NtacF wild-type mice for at least two generations and then maintained and bred continuously with each other as heterozygotes for >10 generations. The MMP-9 KO and MMP-9 WT mice used in this study were always littermates. The experiments were performed on male 2- to 4 month-old mice. For experiments with MMP-9 inhibitor 2- to 3-month-old male Wistar rats were used. All of the animals were group-housed and maintained on a 12 h/12 h light/dark cycle with water and food provided ad libitum. The animals were treated in accordance with the ethical standards of European (directive no. 86/609/EEC) and Polish regulations resulting from this directive. All of the experimental procedures were approved by the Local Ethics Committee. Animals were anesthetized with isoflurane and decapitated. The brains were quickly removed and placed in cold artificial cerebrospinal fluid (aCSF; 117 mM NaCl, 4.7 mM KCl, 2.5 mM NaHCO3, 1.2 mM NaH2PO4, 2.5 mM CaCl2, 1.2 mM MgSO4 and 1 mM glucose), bubbled with carbogen (95% O2 and 5% CO2). Both hemispheres were cut into 400 μm coronal slices with a vibratome. The slices were then transferred to a recording interface chamber and perfused with carbogenated aCSF at 33°C for at least 1 h before the LTP experiments started. Field excitatory postsynaptic potentials (fEPSP) were recorded using glass electrodes (1–3 MΩ resistance). Electrodes positions are shown in Figure 1. Test pulses at 0.033 Hz, 0.1 ms, were delivered by a bipolar metal electrode (FHC). The intensity of a test stimulus was adjusted to obtain fEPSP with amplitude that amounted to a half of the maximal response. After at least 15 min of stable baseline recording, a theta burst protocol (TBS) was used to evoke LTP. Three trains of stimuli were applied every 5 min. One train was composed of five sequences of pulses separated by 1 s. Each sequence consisted of five bursts of stimuli at 5 Hz. The bursts consisted of eight pulses at 100 Hz. After the end of the theta burst protocol, test pulses were subsequently applied for at least 90 min. Recordings were amplified and digitized, and amplitudes were analyzed online and off-line (CED, Cambridge, UK). The same protocol was used in the experiments with S24994 (Hanessian et al., 2001; Jourquin et al., 2003), a specific MMP-9 inhibitor. After 15 min of baseline recordings S24994 was delivered (100 nM), and, 15 min later, TBS protocol was used to induce LTP. S24994 was present in ACSF throughout all remaining recording time. ANOVA with repeated measures was used for statistical analysis of responses averaged in 5 min intervals; p < 0.05 was considered significant.


Matrix metalloproteinase 9 (MMP-9) is indispensable for long term potentiation in the central and basal but not in the lateral nucleus of the amygdala.

Gorkiewicz T, Balcerzyk M, Kaczmarek L, Knapska E - Front Cell Neurosci (2015)

Genetic inhibition of MMP-9 results in destabilization of LTP in the central and basal but not in the lateral amygdala. (A) fEPSP in the EC–LA amygdala pathway was similar in slices from mice lacking functional MMP-9 gene (MMP-9 KO, open circles n = 6) and control animals (WT, filled circles, n = 5). (B) fEPSP evoked in the LA-BA pathway in slices from MMP-9 KO mice (open circles, n = 7) within first 70 min had the same magnitude as LTP in slices from control animals (WT, filled circles, n = 7); however afterwards it went down to the baseline level. (C) fEPSP induced in the BA-CeAm pathway in slices from MMP-9 KO mice (open circles, n = 7) had the same amplitude as LTP evoked in control slices (filled circles, n = 7) within first 30 min after induction. Then, LTP in MMP-9 KO slices gradually decreased to the baseline level. Left panels show graphs with time course of maximal EPSP amplitudes normalized to baseline. Black arrows mark the time of application of TBS stimulation. Error bars represent SEM. Middle panels show exemplary traces of fEPSP recorded 10 min before (black) and 15 and 90 min after (gray) induction of LTP. Scale bars = 0.2 mV and 5 ms. Right panels present photographs of mouse amygdala (Nissl staining) with positions of stimulating (red arrow) and recording (black arrow) electrodes.
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Figure 1: Genetic inhibition of MMP-9 results in destabilization of LTP in the central and basal but not in the lateral amygdala. (A) fEPSP in the EC–LA amygdala pathway was similar in slices from mice lacking functional MMP-9 gene (MMP-9 KO, open circles n = 6) and control animals (WT, filled circles, n = 5). (B) fEPSP evoked in the LA-BA pathway in slices from MMP-9 KO mice (open circles, n = 7) within first 70 min had the same magnitude as LTP in slices from control animals (WT, filled circles, n = 7); however afterwards it went down to the baseline level. (C) fEPSP induced in the BA-CeAm pathway in slices from MMP-9 KO mice (open circles, n = 7) had the same amplitude as LTP evoked in control slices (filled circles, n = 7) within first 30 min after induction. Then, LTP in MMP-9 KO slices gradually decreased to the baseline level. Left panels show graphs with time course of maximal EPSP amplitudes normalized to baseline. Black arrows mark the time of application of TBS stimulation. Error bars represent SEM. Middle panels show exemplary traces of fEPSP recorded 10 min before (black) and 15 and 90 min after (gray) induction of LTP. Scale bars = 0.2 mV and 5 ms. Right panels present photographs of mouse amygdala (Nissl staining) with positions of stimulating (red arrow) and recording (black arrow) electrodes.
Mentions: MMP-9 homozygous knock-out mice on a C57BL/6 background were obtained from Dr. Z. Werb (University of California, San Francisco). These mice were bred with C57BL/6NtacF wild-type mice for at least two generations and then maintained and bred continuously with each other as heterozygotes for >10 generations. The MMP-9 KO and MMP-9 WT mice used in this study were always littermates. The experiments were performed on male 2- to 4 month-old mice. For experiments with MMP-9 inhibitor 2- to 3-month-old male Wistar rats were used. All of the animals were group-housed and maintained on a 12 h/12 h light/dark cycle with water and food provided ad libitum. The animals were treated in accordance with the ethical standards of European (directive no. 86/609/EEC) and Polish regulations resulting from this directive. All of the experimental procedures were approved by the Local Ethics Committee. Animals were anesthetized with isoflurane and decapitated. The brains were quickly removed and placed in cold artificial cerebrospinal fluid (aCSF; 117 mM NaCl, 4.7 mM KCl, 2.5 mM NaHCO3, 1.2 mM NaH2PO4, 2.5 mM CaCl2, 1.2 mM MgSO4 and 1 mM glucose), bubbled with carbogen (95% O2 and 5% CO2). Both hemispheres were cut into 400 μm coronal slices with a vibratome. The slices were then transferred to a recording interface chamber and perfused with carbogenated aCSF at 33°C for at least 1 h before the LTP experiments started. Field excitatory postsynaptic potentials (fEPSP) were recorded using glass electrodes (1–3 MΩ resistance). Electrodes positions are shown in Figure 1. Test pulses at 0.033 Hz, 0.1 ms, were delivered by a bipolar metal electrode (FHC). The intensity of a test stimulus was adjusted to obtain fEPSP with amplitude that amounted to a half of the maximal response. After at least 15 min of stable baseline recording, a theta burst protocol (TBS) was used to evoke LTP. Three trains of stimuli were applied every 5 min. One train was composed of five sequences of pulses separated by 1 s. Each sequence consisted of five bursts of stimuli at 5 Hz. The bursts consisted of eight pulses at 100 Hz. After the end of the theta burst protocol, test pulses were subsequently applied for at least 90 min. Recordings were amplified and digitized, and amplitudes were analyzed online and off-line (CED, Cambridge, UK). The same protocol was used in the experiments with S24994 (Hanessian et al., 2001; Jourquin et al., 2003), a specific MMP-9 inhibitor. After 15 min of baseline recordings S24994 was delivered (100 nM), and, 15 min later, TBS protocol was used to induce LTP. S24994 was present in ACSF throughout all remaining recording time. ANOVA with repeated measures was used for statistical analysis of responses averaged in 5 min intervals; p < 0.05 was considered significant.

Bottom Line: In the present study we show that LTP in the basal and central but not lateral amygdala (LA) is affected by MMP-9 knock-out.The MMP-9 dependency of LTP was confirmed in brain slices treated with a specific MMP-9 inhibitor.The results suggest that MMP-9 plays different roles in synaptic plasticity in different nuclei of the amygdala.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurophysiology, Nencki Institute of Experimental Biology, Polish Academy of Sciences Warszawa, Poland ; Department of Biophysics, Warsaw University of Life Sciences Warszawa, Poland.

ABSTRACT
It has been shown that matrix metalloproteinase 9 (MMP-9) is required for synaptic plasticity, learning and memory. In particular, MMP-9 involvement in long-term potentiation (LTP, the model of synaptic plasticity) in the hippocampus and prefrontal cortex has previously been demonstrated. Recent data suggest the role of MMP-9 in amygdala-dependent learning and memory. Nothing is known, however, about its physiological correlates in the specific pathways in the amygdala. In the present study we show that LTP in the basal and central but not lateral amygdala (LA) is affected by MMP-9 knock-out. The MMP-9 dependency of LTP was confirmed in brain slices treated with a specific MMP-9 inhibitor. The results suggest that MMP-9 plays different roles in synaptic plasticity in different nuclei of the amygdala.

No MeSH data available.