Substance P-Immunopositive Neurons in Rat Spinal Nerve Sensory Ganglia during Postnatal Ontogeny

We report here immunohistochemical studies addressing substance P (SP)-containing neurons in the spinal nerve sensory ganglia of rats (n = 30) aged 10–90 days. The results showed that SP-immunopositive neurons are present in these ganglia from the moment of birth. The number of SP-containing neurons decreased with age to day 10 of life. SP-immunopositive neurons were very small and small cells.