Distribution and Seasonal Variation in Hypothalamic RF‐amide Peptides in a Semi‐Desert Rodent,the Jerboa

The jerboa is a semi‐desert rodent, in which reproductive activity depends on the seasons, being sexually active in the spring–summer. The present study aimed to determine whether the expression of two RF‐amide peptides recently described to regulate gonadotrophin‐releasing hormone neurone activity, kisspeptin (Kp) and RF‐amide‐related peptide (RFRP)‐3, displays seasonal variation in jerboa. Kp and/or RFRP‐3 immunoreactivity was investigated in the hypothalamus of jerboas captured in the field of the Middle Atlas mountain (Morocco), either in the spring or autumn. As in other rodents, the Kp‐immunoreactive (‐IR) neurones were found in the anteroventro‐periventricular and arcuate nuclei. RFRP‐3 neurones were noted within the dorso/ventromedial hypothalamus. A marked sexual dimorphism in the expression of Kp (but not RFRP‐3) was observed. The number of Kp‐IR neurones was nine‐fold higher, and the density of Kp‐IR fibres and terminal‐like elements in the median eminence was two‐fold higher in females than in males. Furthermore, a significant seasonal variation in peptide expression was obtained with an increase in both Kp‐ and RFRP‐3‐IR cell bodies in sexually active male jerboas captured in the spring compared to sexually inactive autumn animals. In the arcuate nucleus, the level of Kp‐IR cells and fibres was significant higher during the sexually active period in the spring than during the autumnal sexual quiescence. Similarly, the number of RFRP‐3‐IR neurones in the ventro/dorsomedial hypothalamus was approximately three‐fold higher in sexually active jerboa captured in the spring compared to sexually inactive autumn animals. Altogether, the present study reports the distribution of Kp and RFRP‐3 neurones in the hypothalamus of a desert species and reveals a seasonal difference in their expression that correlates with sexual activity. These findings suggest that these two RF‐amide peptides may act in concert to synchronise the gonadotrophic activity of jerboas with the seasons.