Oxytocin Knockout Mice Demonstrate Enhanced Intake of Sweet and Non-Sweet Carbohydrate Solutions

摘要

Oxytocin knockout (OT KO) mice display enhanced intake of nutritive and non-nutritive sweet solutions (i.e., sucrose and saccharin) compared to wild type (WT) mice of the same C57BL/6 background strain. The present study further investigated the differential behavioral response of OT KO and WT mice to sucrose solutions, and also examined intake preferences of OT KO and WT mice for palatable but non-sweet isocaloric solutions of carbohydrate and fat. A progressive ratio operant licking procedure demonstrated that OT KO and WT mice display a similar motivational drive to consume 10% sucrose. A series of two-bottle intake tests revealed that OT KO mice consume significantly larger amounts of both sweet and non-sweet carbohydrate solutions (i.e., sucrose, Polycose, and cornstarch) compared to WT cohorts. Lick pattern analyses revealed that OT KO mice overconsume carbohydrate solutions by initiating more drinking bouts compared to WT mice; bout sizes did not differ between the genotypes. In contrast, OT KO and WT mice did not differ in their intake of Intralipid, a palatable soybean oil emulsion. These findings indicate that the absence of OT in mice does not affect their appetitive drive to consume palatable sucrose solutions. Instead, the absence of OT may increase daily intake of palatable sweet and non-sweet solutions of carbohydrate (but not fat) by selectively blunting or masking processes that contribute to post-ingestive satiety.