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Nerve growth factor stimulates the development of substance P in sensory ganglia
Insights
Substance P (SP) in rat dorsal root ganglia (DRG) increases with age. Nerve growth factor (NGF) influences SP development, suggesting a role in limb-DRG interactions, though not essential for survival.
Area of Science:
- Neuroscience
- Developmental Biology
Background:
- Substance P (SP) is a putative neurotransmitter.
- Dorsal root ganglia (DRG) are crucial for sensory information processing.
Purpose of the Study:
- To define the in vivo development of SP in rat DRG.
- To investigate the influence of nerve growth factor (NGF) and limb innervation on SP development.
Main Methods:
- Measurement of SP content in rat DRG at different developmental stages.
- Forelimb amputation and NGF administration in neonatal rats.
- Analysis of ganglionic protein content.
Main Results:
- SP content in rat DRG increases significantly during the first 5 weeks of life.
- Forelimb amputation partially inhibited SP developmental increase.
- NGF treatment enhanced SP levels and prevented the inhibitory effects of amputation.
- Antiserum to NGF did not significantly inhibit SP development.
Conclusions:
- SP is a reliable indicator of DRG neuron maturation.
- NGF plays a role in mediating limb-DRG interactions during development.
- Neonatal DRG may retain NGF responsiveness without requiring NGF for survival.
Abstract:
The development of the putative neurotransmitter substance P (SP) in rat dorsal root ganglion (DRG) was defined in vivo. The sixth cervical DRG of newborn rats contained 70 pg of SP, and the ganglionic content increased 5.5-fold during the first 5 weeks of life. Forelimb amputation partially prevented the normal developmental increase of SP in the sixth cervical DRG destined to innervate that limb. Conversely, treatment with nerve growth factor (NGF) increased both ganglionic SP and total ganglion protein. Moreover, NGF administration prevented the failure of SP development that followed amputation, suggesting that NGF may mediate the limb-DRG interaction. However, treatment with antiserum to NGF failed to significantly inhibit development of ganglion SP. Consequently, neonatal ganglia may remain responsive to NGF, without requiring the protein for survival. SP appears to be an excellent index of the maturation of neurons in dorsal root ganglia.