Changes of the nitric oxide synthase-positive and nestin-positive neurons in the basal forebrain of castrated adult male rats following androgen replacement therapy

Ling GUO; Huaqiao WANG; Qunfang YUAN; Zhibin YAO

ABSTRACT

BACKGROUND:

The neurons in the medial septum (MS), vertical and horizontal limbs of diagonal band of Broca (vDB and hDB) in the basal forebrain contain rich androgen receptors (ARs) and estrogen receptors (ERs) by which androgen and estrogen can act dramatically on the neurons in the basal forebrain, subsequently affecting learning and memory processes.

OBJECTIVE:

To qualitatively and quantitatively investigate the effects of androgen replacement therapy on the nitric oxide synthase (NOS)-positive and nestin-positive neurons in the MS, vDB and hDB of castrated adult male rats.

DESIGN:

A randomly controlled study on experimental animals.

SETTING:

Department of Anatomy and Brain Research Laboratory of Zhngshan Medical College of Sun Yat-sen University.MATERIALS The experiment was performed at Department of Anatomy and Brain Research Laboratory of Zhongshan Medical College of Sun Yatsen University from June 2001 to June 2002. Totally twenty-eight adult male Sprague-Dawley rats were randomly divided into four groups with seven rats in each group androgen replacement therapy for 4 weeks following 24 hours of castration (ART1), androgen replacement therapy for 2 weeks following 2 weeks of castration (ART2), vehicle replacement therapy for 4weeks following 24 hours of castration (VRT), sham-operated group (Sham).

INTERVENTIONS:

① ART1 group The castrated rats received subcutaneous injection of testosterone proprionate (25 mg/kg) dissolved in 100 μL of sterile sesame oil every other day from 1030 am to 1100 am for 14 times (4 weeks). ② ART2 group The castrated rats received subcutaneous injection of testosterone proprionate with the same dosage and method as ART1 group for 7 times (2 weeks). ③ The rats in VRT group received subcutaneous injection of 100μL of sterile sesame oil for 14 times (4 weeks) by the same regime as described above. ④ Rats in Sham group only received sham-operated treatments, and testes were intact and lived for 4 weeks.MAIN OUTCOME

MEASURES:

Morphology and counts of NOS-positive and nestin-positive neurons were observed in the MS, vDB and hDB with immunohistochemical method at various time points.

RESULTS:

Data of totally 28 rats were involved in the final analyses. ①Morphological features of both NOS-positive and nestin-positive neurons in the MS, vDB and hDB were not significantly changed among four groups. ② The number of NOS-positive and nestin-positive neurons in the MS and vDB of VRT group were significantly higher than those of Sham group (P＜ 0.05 or 0.01), whereas the numbers of the NOS-positive and nestin-posi-tive neurons in the MS and vDB of ART1 and ART2 groups was significantly lower than those of VRT group (P ＜ 0.05 or 0.01), which nearly reached the levels of sham group (P ＞ 0.05).

CONCLUSION:

Androgen replacement therapy produces no significant effects on the morphological features of NOS-positive and nestin-positive neurons, but the therapy can selectively decrease the numbers of NOS-positive and nestin-positive neurons in different subregions of the basal forebrain, which may be closely related to androgen downregulation of expressions of NOS and nestin by ARs-mediated mechanisms, thereby producing complex effects on learning and memory processes.