Sex Differences in Taste Neophobia and Conditioned Aversion Across Fluid Administration Methods

Abstract

Rodent studies of the taste system commonly employ two methods of taste administration (MOA): active licking from spouts or intra-oral cannula (IOC) deliveries. While bottle drinking preserves natural consumption behavior, IOC administration, where animals receive liquids passively into their oral cavity, provides precise temporal control of stimulus delivery but limits the reliability of measuring voluntary intake and hedonic response. To overcome these limitations, a third method, nose-poke for IOC delivery (NP-IOC), was introduced. In NP-IOC, each taste is delivered through the IOC following an active nose poke, thus combining voluntary decision-making with temporal precision. Whether NP-IOC preserves natural taste-guided behavior, however, remains unknown. Here, we examined how NP-IOC affects taste neophobia (the reluctance to consume novel tastes) and conditioned taste aversion (CTA, avoidance of a taste paired with malaise). Rats received water either via standard bottle licking (control) or through the NP-IOC system. Following habituation, animals were tested for neophobia using low-neophobic (LN) sucrose or high-neophobic (HN) saccharin solutions, followed by CTA training via lithium chloride injection. Our results showed sexual differences in neophobia using NP-IOC: males preserved the expected difference between LN and HN tastes, whereas females showed attenuated neophobia, eliminating the typical HN avoidance observed with bottle administration. Nevertheless, CTA learning remained robust across sexes and MOAs. Deeper analysis of this seemingly similar learned aversion, however, revealed again sex differences: while male rats showed strong CTA regardless of pre-CTA consumption, females maintained a correlation between pre-and post-CTA consumption under both MOAs, suggesting sex-specific taste learning patterns. These findings support the use of NP-IOC in taste research that requires both precise stimulus control and voluntary behavior, while also underscoring the necessity of exploring divergent behavioral strategies and the associated brain circuits in males and females.