Abstract
The ability of the adult brain to undergo plastic changes is of particular interest in medicine, especially regarding recovery from injuries or improving learning and cognition. Matrix metalloproteinases (MMPs) have been associated with juvenile experience-dependent primary visual cortex (V1) plasticity, yet little is known about their role in this process in the adult V1. Activation of MMPs is a crucial step facilitating structural changes in a healthy brain; however, upon brain injury, upregulated MMPs promote the spread of a lesion and impair recovery. To clarify these seemingly opposing outcomes of MMP-activation, we examined the effects of MMP-inhibition on experience-induced plasticity in healthy and stoke-affected adult mice. In healthy animals, 7-day application of MMP-inhibitor prevented visual plasticity. Additionally, treatment with MMP-inhibitor once but not twice following stroke rescued plasticity, normally lost under these conditions. Our data imply that an optimal level of MMP-activity is crucial for adult visual plasticity to occur.
Highlights
Neuroplasticity is the ability of the brain to adapt both structurally and functionally to changing patterns of activity induced by the environment or intrinsic factors
Since it is believed that the mechanisms underlying juvenile and adult ODplasticity are different (Hofer et al, 2006; Sato and Stryker, 2008; Ranson et al, 2012), we aimed to test whether matrix metalloproteinases (MMPs) play a significant role in adult V1-plasticity, in which open-eye potentiation is a major component mediating these changes
Control and GM6001-treated mice without MD (Figure 1A,B) the activity patch induced by stimulation of the contralateral eye was darker than that of the ipsilateral eye; the ocular dominance (OD)-index (ODI) was positive and warm colors dominated the OD-map, indicating typical contralateral eye dominance in V1. 7 days of MD induced an OD-shift towards the open eye in control (Figure 1C) but not in GM6001-treated mice (Figure 1D): in control mice after MD visual stimulation of the contralateral and ipsilateral eye activated V1 rather strong; the OD-histogram was shifted to the left and cooler colors appeared in the 2-dimensional OD-map
Summary
Neuroplasticity is the ability of the brain to adapt both structurally and functionally to changing patterns of activity induced by the environment or intrinsic factors. V1 consists of a monocular and a binocular zone; neurons in the binocular zone respond to stimulation of both eyes but are dominated by the contralateral eye in rodents (Drager, 1975; 1978). This ocular dominance (OD) can be modified in an experience-dependent manner, by depriving one eye of pattern vision for several days (known as monocular deprivation or MD), as originally observed by Wiesel and Hubel more than 50 years ago (Wiesel and Hubel, 1965).
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