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Postnatal development of vasoactive intestinal polypeptide-containing neurons in the visual cortex of normal and
H Michaloudi1, G C Papadopoulos, J Antonopoulos
1Department of Anatomy, School of Veterinary Medicine, University of Thessaloniki, Greece.
Insights
Dark rearing in rats preserves vasoactive intestinal polypeptide (VIP)-containing neurons in visual cortex development. Postnatal darkness prevents the typical age-related decrease in VIP neuron density, leading to higher numbers in adulthood.
Area of Science:
- Neuroscience
- Developmental Biology
- Visual System Research
Background:
- Vasoactive intestinal polypeptide (VIP) neurons play a role in cortical development.
- Visual experience influences neuronal development in the visual cortex.
- The impact of early-life sensory deprivation on VIP neuron populations is not fully understood.
Purpose of the Study:
- To investigate the effects of dark rearing on VIP neuron distribution and density.
- To examine how postnatal visual deprivation impacts VIP neuron development in rat visual cortical areas.
- To compare VIP neuron populations in dark-reared versus normally reared rats.
Main Methods:
- Immunohistochemical analysis of VIP-containing neurons in rat visual cortical areas (17, 18, 18a).
- Comparison of Wistar rats reared under normal light versus complete darkness from birth.
- Quantitative assessment of VIP neuron density at various postnatal developmental stages (P7 to 60 days).
Main Results:
- VIP neurons were predominantly found in layers II and III of visual cortical areas.
- VIP neuron development showed similar initial patterns in both normal and dark-reared rats.
- Dark rearing resulted in significantly higher VIP neuron densities from P21 onwards, with adult densities being 49-57% greater than controls.
Conclusions:
- Normal postnatal visual experience is crucial for the typical age-dependent reduction in VIP neuron numbers.
- Dark rearing significantly attenuates the decline in VIP neuron density during postnatal development.
- Sensory experience critically modulates the survival and density of specific neuronal populations in the developing visual cortex.
Abstract:
The effects of dark rearing on the distribution and density of vasoactive intestinal polypeptide (VIP)-containing neurons in the visual cortical areas (17, 18 and 18a) of rats during postnatal development were examined immunohistochemically. Two groups of Wistar rats, one reared under normal lighting conditions and the other in complete darkness from birth, were used. VIP neurons showed a fairly similar distribution in the three visual areas, being predominantly present in layers II and III. Their pattern of development was found to be similar in the normal and dark-reared animals and was characterized by a marked increase from postnatal day (P) 7 to P21, followed by a gradual diminution to 24-31% of peak densities. Counts of labeled neurons at all ages examined showed that their density was similar in both groups at P7 and P14, but progressively greater in dark-reared animals from P21 and thereafter, so that they only fell to 38-43% of peak densities. Thus, by 60 days of age densities of VIP-labeled neurons in areas 17, 18 and 18a in dark-reared rats were 57%, 49% and 51% higher than in the corresponding areas of the age-matched control rats. These results indicate that the normal decline in the numbers of VIP neurons is not so marked under the conditions of dark rearing.