Effects of Visual Experience on Vascular Endothelial Growth Factor Expression during the Postnatal Development of the Rat Visual Cortex

Abstract

The development of the cortical vascular network depends on functional maturation. External inputs are an essential requirement in the modeling of the visual cortex, mainly during the critical period, when the functional and structural properties of visual cortical neurons are particularly susceptible to alterations. Vascular endothelial growth factor (VEGF) is the major angiogenic factor, a key signal in the induction of vessel growth. Our study focused on the role of visual stimuli on the development of the vascular pattern correlated with VEGF levels. Vascular density and the expression of VEGF were examined in the primary visual cortex of rats reared under different visual environments (dark rearing, dark-rearing in conditions of enriched environment, enriched environment, and laboratory standard conditions) during postnatal development (before, during, and after the critical period). Our results show a restricted VEGF cellular expression to astroglial cells. Quantitative differences appeared during the critical period: higher vascular density and VEGF protein levels were found in the enriched environment group; both dark-reared groups showed lower vascular density and VEGF levels, which means that enriched environment without the physical exercise component does not exert effects in dark-reared rats.

Effect of intracortical vascular endothelial growth factor infusion and blockade during the critical period in the rat visual cortex

“…As we reported previously (Bengoetxea et al, 2008), the increase in vascular density during the critical period of the visual cortex runs parallel to the increase of VEGF levels. Our results show that although the infusion of VEGF does not reach control values, it is still significantly higher than in anti-VEGF-infused animals, this trend being similar to the trend in vascular or neuronal density quantifications.…”

“…Our previous results suggest that the increase of experience induces an increase in vascular density mediated by a peak in the secretion of VEGF. This peak occurs at the 4th postnatal week, shortly after the end of the minipump placement (Bengoetxea et al, 2008). The implantation-produced lesion induces a significantly lower increase of vascular density, which is one of the changes related to the postnatal maturation of the visual cortex (Argandoñ a and Lafuente, 1996Lafuente, , 2000Lafuente, , 2002Argandoñ a et al, 2005;Bengoetxea et al, 2008).…”

“…This peak occurs at the 4th postnatal week, shortly after the end of the minipump placement (Bengoetxea et al, 2008). The implantation-produced lesion induces a significantly lower increase of vascular density, which is one of the changes related to the postnatal maturation of the visual cortex (Argandoñ a and Lafuente, 1996Lafuente, , 2000Lafuente, , 2002Argandoñ a et al, 2005;Bengoetxea et al, 2008). Several authors have reported that brain injuries in developing animals generate a delay in plasticity without gross morphological damage (Prins et al, 1996;Fineman et al, 2000;Adelson et al, 2001;Argandoñ a et al, 2006;Gurkoff et al, 2006).…”

“…These changes lead to an increase in metabolic demand (Black et al, 1990;Harrison et al, 2002) that is satisfied by the adaptive remodeling of the vascular network (Sirevaag et al, 1988;Argandoñ a and Lafuente, 1996;Tieman et al, 2004;Bengoetxea et al, 2008).…”

VEGF reverts the cognitive impairment induced by a focal traumatic brain injury during the development of rats raised under environmental enrichment

“…Whereas initial studies showed that EE modified cortical weight [20,21], subsequent studies described an increase of nuclear and soma size in neurons, dendritic branching or synapsis size [22][23][24] among other effects. Moreover, EE also increases neurogenesis in the hippocampus [13] as it increases the expression of angioglioneurins such as VEGF or BDNF [25][26][27]. Therefore, EE has strong effects on the plasticity of neural connections, especially in the visual cortex [28].…”