RNA Interference of Gonadotropin-Inhibitory Hormone Gene Induces Arousal in Songbirds

Abstract

Gonadotropin-inhibitory hormone (GnIH) was originally identified in quail as a hypothalamic neuropeptide inhibitor of pituitary gonadotropin synthesis and release. However, GnIH neuronal fibers do not only terminate in the median eminence to control anterior pituitary function but also extend widely in the brain, suggesting it has multiple roles in the regulation of behavior. To identify the role of GnIH neurons in the regulation of behavior, we investigated the effect of RNA interference (RNAi) of the GnIH gene on the behavior of white-crowned sparrows, a highly social songbird species. Administration of small interfering RNA against GnIH precursor mRNA into the third ventricle of male and female birds reduced resting time, spontaneous production of complex vocalizations, and stimulated brief agonistic vocalizations. GnIH RNAi further enhanced song production of short duration in male birds when they were challenged by playbacks of novel male songs. These behaviors resembled those of breeding birds during territorial defense. The overall results suggest that GnIH gene silencing induces arousal. In addition, the activities of male and female birds were negatively correlated with GnIH mRNA expression in the paraventricular nucleus. Density of GnIH neuronal fibers in the ventral tegmental area was decreased by GnIH RNAi treatment in female birds, and the number of gonadotropin-releasing hormone neurons that received close appositions of GnIH neuronal fiber terminals was negatively correlated with the activity of male birds. In summary, GnIH may decrease arousal level resulting in the inhibition of specific motivated behavior such as in reproductive contexts.

Seasonal Changes in Hypothalamic Gonadotropin Inhibitory Hormone Expression in the Paraventricular Nucleus of Chukar Partridge (Alectoris chukar)

“…The present study showed that GnIH-ir neurons were primarily found in PVN of both male and female partridges as already were reported in quail (Tsutsui et al, 2000;Ubuka et al, 2003), song and house sparrows (Bentley et al, 2003), white crowned sparrows (Osugi et al, 2004;Ubuka et al, 2012), and European starlings (Ubuka et al, 2008). Few GnIH positive neurons were also observed in DMN, consistent with the findings in zebra finch (Tobari et al, 2010) and sparrow (Small et al, 2008).…”

RNA interference of gonadotropin-inhibitory hormone gene induces aggressive and sexual behaviors in birds

“…The time spent for feeding and the numbers of hopping and pointing were also measured. GnIH gene silencing significantly increased spontaneous activities in both male and female birds [57]. GnIH RNAi made the birds very active, similar to the behavior of birds when they were challenged by novel male song playbacks [57].…”

“…GnIH RNAi made the birds very active, similar to the behavior of birds when they were challenged by novel male song playbacks [57]. On the other hand, there was no statistical difference in the time spent for feeding and the numbers of hopping and pointing between the groups [57].…”

“…It was shown that central administration of GnIH siRNA can significantly reduce GnIH precursor mRNA and GnIH expression and change the activities of birds, thus validating the effect of direct administration of siRNA into the brain in birds [57]. There are also other reports showing that direct administration of siRNA into the central nervous system can effectively silence the target mRNA expression in the brain resulting in changes in physiology and behavior [11,15,21,24,43,44].…”

“…GnIH precursor mRNA expression in the PVN was also analyzed by in situ hybridization. The details of the methods are described in Ubuka et al [57].…”