Testosterone-induced enhancement of male medial preoptic tissue transplant volume in female recipients: a possible neuronotrophic action

Abstract

To characterize further the action of gonadal hormones on the development of the brain, this study was designed to test the ability of testosterone treatment to modify the volume of male brain tissue transplants in female recipients. One-day-old females, in addition to having either medial preoptic area (MPOA) or caudate nucleus (CN) tissue from neonatal males bilaterally implanted into their own MPOA, also received a subcutaneous injection of either 200 μg testosterone propionate (TP) or oil concurrently, and on the following 4 days. All recipients were sacrificed at 30 days of age postnatally. An analysis of male transplant volumes indicated that MPOA transplants in oil-treated recipients were substantially reduced in size (0.06 ± 0.01 mm 3) compared with the initial transplant volume of 0.19 mm 3. However, MPOA transplants in recipients treated with TP showed a 79% increase above the initial transplant volume (to 0.34 ± 0.05 mm 3). The resulting 5- to 6-fold difference in MPOA transplant volume between oil and TP treated animals was highly significant. In sharp contrast, the same TP treatment to recipients receiving male CN transplants resulted in no enhancement of transplant volume. Therefore, transplants involving a brain area known to concentrate 3H-labeled testosterone neonatally (i.e. the MPOA) responded to TP treatment with an enhancement of volume which was not observed for transplants consisting of brain tissue not known to concentrate 3H-labeled testosterone (i.e. the CN). The above results suggest that testosterone is a ‘neuronotrophic” agent during development that acts specifically on cells within steroid-sensitive brain areas, perhaps to prevent neuronal death within these areas.