Food scarcity suppresses Kiss1 signaling in the anterior hypothalamus of tundra vole males
Kiss1 expressing neurons in the anterior hypothalamus are located in the POA, which is involved in temperature regulation (Hrvatin et al., 2020; Takahashi et al., 2020). Kiss1 expression in the anterior hypothalamus is decreased at high workload in tundra vole males (Fig. 2G, Table S4), whereas Kiss1 is close to zero in all groups of common voles (Fig. 2E, F; Table S4). Surprisingly, Kiss1expression in the anterior hypothalamus was not affected by temperature (Fig. 2E-H, Table S4). Anterior hypothalamic Kiss1 shows a positive relationship with gonadal weight only in tundra vole males at high workload (Fig. 3E-H). This finding indicates that the Kiss1system is involved in modifying photoperiodic responses when food is scarce in tundra voles, but not in common voles.
Perikarya of GnRH neurons are also located in the POA and increased frequency of pulsatile release of GnRH through axonal projections into the median eminence is described to regulate gonadotropin release in the pars distalis of the pituitary gland (Lincoln & Fraser, 1979). Surprisingly, Gnrh expression in the anterior hypothalamus was not affected by workload nor temperature (Fig. 2E-H, Table S4).
Fitted linear models revealed that reproductive organ mass can be best predicted by: Tshβ and Tshr in common vole males (F 2,23 = 7.44, p < 0.01);Tshβ in common vole females (F 1,23 = 4.89,p < 0.05); Tshβ, Rfrp, anterior hypothalamicKiss1 in tundra vole males (F 3,28 = 8.47,p < 0.001); Tshβ and anterior hypothalamicKiss1 in tundra vole females (F 2,21 = 3.84, p < 0.05).