Aim: To elucidate the distribution and regulation of Neuropeptide Y (NPY) gene expression in testes under physiological and pathophysiological conditions, such as testicular development, fasting and experimental cryptorchidism.

Methods: In the first experiment, C57BL/6J male mice at the ages of 3 days as well as 2, 3, 5 and 8 weeks were used. In the second and third experiments, adult C57BL/6J male mice were subjected to fasting for 48 h and experimental cryptorchidism for 72 h. The NPY transcripts were detected by isotopic in situ hybridization histochemistry.

Results: The NPY transcripts were exclusively expressed in the interstitial cells regardless of the age groups and experimental conditions. The NPY mRNA levels were found to increase significantly with age (from the neonatal to prepubertal period [P < 0.01] and from the prepubetal to postpubertal period [P < 0.01]). Food deprivation for 48 h resulted in a significant increase in the NPY mRNA levels in the arcuate nucleus of the hypothalamus (P < 0.01), but not in the testes. Experimental cryptorchidism for 72 h failed to regulate the NPY gene expression in the testes.

Conclusion: NPY gene expression is distributed in Leydig cells and increases in line with testicular development. The regulation of testicular NPY is different from that of hypothalamic NPY.

Keywords: Neuropeptide Y, testes, in situ hybridization histochemistry, steroidogenesis, androgen, testicular development, cryptorchidism

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