Meeting Abstract

146.3  Monday, Jan. 7  Time-course of expression of ZENK in auditory brain regions and gonadotropin-releasing hormone�”1 cells in starlings in response to song playback ALWARD, B.A.*; ROWND, K.R.; BALL, G.F.; Johns Hopkins University balward1@jhu.edu

Cues such as day length or social context modulate activity of the hypothalamic-pituitary-gonadal (HPG) axis so it is active at appropriate times. Song has been shown to stimulate luteinizing hormone release. However, the neural pathways mediating connections between auditory areas and the gonadotropin-releasing hormone-1 (GnRH-1) neuronal system and the timing of this stimulation are unclear. Here, we examined the expression of the immediate early gene ZENK in three auditory brain regions–the caudomedial mesopallium (CMM), caudomedial nidopallium (NCM), and nucleus mesencephalicus (MLd)–to understand how activity in these regions relates to the time-course of expression of ZENK in GnRH-1 cells. Birds heard song and we extracted their brains after 1.5, 3, 6 or 27-hrs. A no-song group was also used. We quantified ZENK cells in the CMM, NCM, MLd, and GnRH-1 cells of the POA. As expected, song induced increases in ZENK expression in CMM, NCM, and MLd in the 1.5-hr group as compared to the no-song group. ZENK in NCM of the 1.5-hr group was higher than all other groups and the 3-hr group had more ZENK than the 27-hr and no-song group. In CMM, males had more ZENK at 27-hrs than females, but there was no sex difference at 1.5-hrs. In MLd, the 1.5-hr group had more ZENK than the no-song and 27-hr group. For GnRH-ZENK cells we combined the 1.5, 3 and 6-hr groups into a ‘1st-day’ group as they had almost identical means. The 27-hr group had more GnRH-ZENK compared to the 1st-day and no-song group, which were not different. These results suggest that song continues to affect the HPG axis a day after it is heard. Further analysis is needed to identify areas involved in the transfer of information from auditory brain areas to the GnRH-1 system.