Negative Correlation between Neuropeptide Y Profile in the Cerebrospinal Fluid and Growth Hormone Pulses in the Peripheral Circulation in Goats

Abstract

Background/Aims: Growth hormone (GH) is secreted in pulsatile fashion, but the involvement of neuropeptides in the generation of GH pulses is not fully understood. The present study was conducted to elucidate the relationship between GH pulses and neuropeptide levels in the cerebrospinal fluid (CSF) of the third ventricle in ovariectomized goats. Methods: CSF and plasma samples were collected every 15 min. Levels of plasma GH and profiles of GH-releasing hormone (GHRH), somatostatin (SRIH) and neuropeptide Y (NPY) in the CSF were measured by radioimmunoassay. Pulse/trough characteristics and correlations were assessed by the ULTRA algorithm, cross-correlation analysis and approximate entropy test. Results: The periodicity of GH pulses was 2.20 h. Although most GH pulses were associated with GHRH peaks, there was no correlation between GH and GHRH or GH and SRIH. NPY levels in the CSF fluctuated episodically at 2.03-hour intervals. GH pulse peaks occurred 0–30 min after NPY troughs, and there was a significant negative cross-correlation and negative synchronicity between GH and NPY profiles. In addition, intracerobroventricular infusion of NPY suppressed GH secretagogue (KP102)-induced GH release. Conclusion: The periodic decrease in NPY may be involved in the generation of GH pulsatility in goats.