Consumption varies across the stages (metestrus, diestrus, proestrus, estrus) of a rat’s estrous cycle, changing in ways that might be expected to reflect, in part, a direct impact of hormones on taste palatability. Evidence regarding this hypothesis has been mixed, however, and critical within-subject experiments comparing consumption of multiple tastes with distinct valences across all estrous phases have been few. Here, we assayed female rats’ licking of palatable (saccharin, sucrose, NaCl) and aversive (quinine-HCl, citric acid) tastes in brief-access trials, while tracking their estrous cycles through vaginal cytology. We observed sucrose palatability to be high at metestrus, the same phase at which the palatability of the aversive citric acid was low. These patterns were consistent across tastes of similar palatability, despite vast differences between the substances’ receptor mechanisms and central impacts. Together, these results reveal a general (i.e., independent of particular tastant identity) magnification of palatability—higher than average for palatable tastes and lower for aversive tastes—centered largely on metestrus. We tested whether this phenomenon reflects lateral hypothalamic (LH) estradiol processing, by infusing LH with an estrogen receptor blocker (ICI182,780) across 5 consecutive tasting sessions. Control infusions replicated the metestrus magnification of palatability; as predicted, ICI infusions blocked this effect, but estrogen receptor inhibition failed to render preferences “cycle free,” instead delaying the palatability magnification until diestrus. In summary, the estrous cycle directly mediates taste palatability in a manner involving hypothalamic actions of estradiol, but this effect is only one of several impacting consumption across the estrous cycle. Significance Statement Consummatory behaviors are altered by numerous factors including naturally circulating hormones. While decades of work has investigated the role of reproductive hormones on consumption, it remains unclear whether (and to what degree) hormone-driven consumption variability is related to changes in central palatability processing. Here we show that taste palatability is indeed directly modulated by estrous phase—during metestrus, the differences between licking to palatable and aversive tastes is magnified—and go on to show that this phenomenon is governed, at least in part, by estradiol processing within the lateral hypothalamus.
Lin et al. (Wed,) studied this question.