Synaptogenic effects of neonatal estradiol treatment in rat superior cervical ganglia.

Neonatal rats treated with testosterone propionate or 17-beta-estradiol during the first two postnatal weeks have more neurons and synapses in their superior cervical ganglia (SCGs) at 15 days of age than do vehicle-treated littermates. To determine whether a non-aromatizable androgen would similarly increase the number of SCG synapses, dihydrotestosterone (DHT) was injected into male rats beginning on the day of birth. The animals were sacrificed on postnatal day 15 and the SCGs removed on postnatal day 15. Counts of synapses showed no difference in the number of synapses between control and DHT-treated animals. These results suggest that the actions of testosterone to increase the numbers of SCG synapses may be via aromatization to estradiol. An additional study was done to determine whether the additional synapses formed in SCGs of animals treated with estradiol arise from neurons whose axons are in the cervical sympathetic trunk or from intrinsic neurons, i.e., SIF cells or other principal ganglion neurons. Neonatal males were injected with 17-beta-estradiol or vehicle beginning on the day of birth and continuing until the time of sacrifice on day 15. The number of intrinsic synapses formed under control and estradiol treatments was determined in SCGs of animals whose extrinsic synapses were caused to degenerate by severing the cervical sympathetic trunk bilaterally on postnatal day 13, two days before sacrifice. The total number of synapses (extrinsic plus intrinsic) in the ganglion after vehicle or estradiol treatment was determined in unoperated animals and used to calculate the number of extrinsic synapses.(ABSTRACT TRUNCATED AT 250 WORDS)