Nerve growth factor (NGF) uptake and transport following injection in the developing rat visual cortex

Area of Science:

• Neuroscience
• Developmental Biology
• Visual System Research

Background:

• Cortical nerve growth factor (NGF) infusions inhibit ocular-dominance plasticity during critical developmental periods.
• The precise mechanisms by which NGF influences visual cortical plasticity remain largely unknown.

Purpose of the Study:

• To investigate the presence and developmental timing of uptake/transport mechanisms for NGF in intracortical and extracortical cells during normal development.
• To elucidate the role of NGF in the developing visual cortex and its plasticity.

Main Methods:

• Intracortical injections of iodinated NGF (125I-NGF) into the occipital cortex of rats at various postnatal ages.
• Analysis of labelled cell distribution within the cortex and in extracortical projection areas like the lateral geniculate nucleus (LGN) and basal forebrain.
• Age-dependent assessment of NGF uptake and retrograde transport in neuronal populations.

Main Results:

• Few NGF-labelled cells were found within the cortex, primarily near the injection site, with numbers varying by age (detected between postnatal days 14-18, absent in adults).
• Neurons in the lateral geniculate nucleus (LGN) did not show NGF uptake or retrograde transport at any age.
• Retrogradely labelled neurons were identified in the basal forebrain, appearing at postnatal day 14 and increasing into adulthood.

Conclusions:

• Both intrinsic cortical neurons and extrinsic neurons (from the basal forebrain) exhibit NGF uptake and transport during the critical period for visual cortical plasticity.
• These findings indicate that NGF may influence visual cortical plasticity through both intra- and extracortical pathways during development.