Development of nNOS-positive preganglionic sympathetic neurons in the rat thoracic spinal cord.

To gain a better understanding of the neuroplasticity of sympathetic neurons during postnatal ontogenesis, the distribution of neuronal nitric oxide synthase (nNOS) immunoreactivity was studied in sympathetic preganglionic neurons (SPN) in the spinal cord (Th2 segment) of female Wistar rats at different ages (newborn, 10-, 20-, 30-day-old; 2-, 6-month-old; 3-year-old). In all age groups, the majority of nNOS-immunoreactive (IR) neurons was observed in the nucleus intermediolateralis thoracolumbalis pars principalis. In the first month, the proportion of nNOS-IR neurons decreased significantly from 92 ± 3.4% in newborn to 55 ± 4.6% in 1-month-old, while the number of choline acetyltransferase (ChAT)-IR neurons increased from 74 ± 4.2% to 99 ± 0.3% respectively. Decreasing nNOS expression in the first 10 days of life was also confirmed by western blot analysis. Some nNOS-IR SPN also colocalized calbindin (CB) and cocaine and amphetamine-regulated transcript (CART). The percentage of NOS(+)/CB(-) SPN increased from 23 ± 3.6% in 10-day-old to 36 ± 4.2% in 2-month-old rats. Meanwhile, the proportion of NOS(+)/CART(-) neurons decreased from 82 ± 4.7% in newborn to 53 ± 6.1% in 1-month-old rats. The information provided here will also serve as a basis for future studies investigating the mechanisms of autonomic neuron development.

Development of nNOS-positive neurons in the rat sensory ganglia after capsaicin treatment.

To gain a better understanding of the neuroplasticity of afferent neurons during postnatal ontogenesis, the distribution of neuronal nitric oxide synthase (nNOS) immunoreactivity was studied in the nodose ganglion (NG) and Th2 and L4 dorsal root ganglia (DRG) from vehicle-treated and capsaicin-treated female Wistar rats at different ages (10-day-old, 20-day-old, 30-day-old, and two-month-old). The percentage of nNOS-immunoreactive (IR) neurons decreased after capsaicin treatment in all studied ganglia in first 20 days of life, from 55.4% to 36.9% in the Th2 DRG, from 54.6% to 26.1% in the L4 DRG and from 37.1% to 15.0% in the NG. However, in the NG, the proportion of nNOS-IR neurons increased after day 20, from 11.8% to 23.9%. In the sensory ganglia of all studied rats, a high proportion of nNOS-IR neurons bound isolectin B4. Approximately 90% of the sensory nNOS-IR neurons bound to IB4 in the DRG and approximately 80% in the NG in capsaicin-treated and vehicle-treated rats. In 10-day-old rats, a large number of nNOS-IR neurons also expressed TrkA, and the proportion of nNOS(+)/TrkA(+) neurons was larger in the capsaicin-treated rats compared with the vehicle-treated animals. During development, the percentage of nNOS(+)/TrkA(+) cells decreased in the first month of life in both groups. The information provided here will also serve as a basis for future studies investigating mechanisms of sensory neuron development.