Synaptogenic effects of neonatal estradiol treatment in rat superior cervical ganglia
Wright, L.L.; Smolen, A.J.
Brain Research 353(2): 161-165
1985
ISSN/ISBN: 0006-8993 PMID: 4041901 DOI: 10.1016/0165-3806(85)90204-4
Accession: 006557179
Neonatal rats treated with testosterone propionate or 17-.beta.-estradiol during the 2 postnatal wk have more neurons and synapses in their superior cervical ganglia (SCG) 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, dihydrotestosteone (DHT) was injected into male rats beginnng on the day of birth. The animals were sacrificed on postnatal day 15 and the SCG removed on postnatal day 15. Counts of synapses showed on difference in the number of synapses between control and DHT-treated animals. The actions of testosteone to increase the number of SCG synapses may be via aromatization to estradiol. An additional study was done to determine whether the additional synapses formed in SCG 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 SCG of animals whose extrinsic synapses were caused to degenerate by servering 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. Results of synapse calculations showed that over 70% of the additional synapses present in SCG of estradiol-treated animals arise from the cervical sympathetic trunk. The additional SCG neurons present after neonatal estradiol treatment receive .apprx., the same ratio of intrinsic to extrinsic synapses as controls, on average, and are thus likely to be normally innervated.