Castration and replacement of gonadal steroids have been used extensively in order to examine the hormonal regulation of song and sexual behaviors in passerine birds. However, recent studies have reported that levels of gonadal hormones may remain high following castration. In order to circumvent this problem, adenohypophysectomy might be advantageous. In this study we describe a technique for removing the anterior pituitary gland in a small passerine species (the zebra finch, Poephila guttata) using a parapharyngeal approach. The completeness of the adenohypophysectomy in individual male and female birds was examined by measuring gonadal weights as well as plasma levels of luteinizing hormone. The results indicate that this technique can be successfully applied to zebra finches. Removal of the anterior pituitary gland may represent a more effective means than gonadectomy for lowering circulating levels of gonadal hormones.
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