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, wh ich 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 16t h day in utero (i.u.) until birth, and subsequently on the 2nd, 5th, 7 th, 12th, 16th, 30th, 42nd postnatal day and in the adult (3 months). In the submandibular ganglion SP- and NKA-IR cells and fibres first ap peared 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 cel ls were immunoreactive to SP and NKA. The number stayed at more than 9 0% 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 ce lls 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. Th e number of SP- and NKA-IR cells increased steadily, reaching a maximu m at the time of birth when 68% (SP) and 74% (NKA) of the ganglion cel ls were immunoreactive. Thereafter they began to decrease toward the l evel of an adult rat (10% SP, 11% NKA). In the superior cervical gangl ion only a few SP- and NKA-IR ganglion cells were detected from the 19 th day i.u. to the fifth postnatal day. Positive ganglion cells were a lso occasionally found in the nerve trunks out-side the superior cervi cal ganglion. From the seventh day onwards no SP- or NKA-IR ganglion c ells were found. SP- and NKA-IR SIF (small intensively fluorescent) ce lls were detected from the 16th postnatal day onwards.