Development of substance P and neurokinin A immunoreactivity in ganglia supplying nerves to the submandibular glands of the rat.

Developing submandibular, trigeminal and superior cervical ganglia, which provide innervation to the submandibular glands, were studied for substance P (SP)- and neurokinin A (NKA)-immunoreactive (IR) ganglion cells and nerve fibres in rat. These ganglia were examined by using an indirect immunofluorescence technique at daily intervals from the 16th day in utero (i.u.) until birth, and subsequently on the 2nd, 5th, 7th, 12th, 16th, 30th, 42nd postnatal day and in the adult (3 months). In the submandibular ganglion SP- and NKA-IR cells and fibres first appeared in considerable numbers on the 19th day i.u. (in one sample out of five on the 18th day i.u.), when more than 90% of the ganglion cells were immunoreactive to SP and NKA. The number stayed at more than 90% to the 7th postnatal day and then slowly decreased to the levels of adult animals (18% SP, 17% NKA). The first SP- and NKA-IR ganglion cells and fibres appeared in the trigeminal ganglion on the 18th day i.u. when they represented 7% (SP) and 4% (NKA) of the ganglion cells. The number of SP- and NKA-IR cells increased steadily, reaching a maximum at the time of birth when 68% (SP) and 74% (NKA) of the ganglion cells were immunoreactive. Thereafter they began to decrease toward the level of an adult rat (10% SP, 11% NKA). In the superior cervical ganglion only a few SP- and NKA-IR ganglion cells were detected from the 19th day i.u. to the fifth postnatal day. Positive ganglion cells were also occasionally found in the nerve trunks outside the superior cervical ganglion.(ABSTRACT TRUNCATED AT 250 WORDS)