CONTINUOUS INTRAORAL SACCHARIN INFUSIONS IN HIGH VS LOW SACCHARIN-CONSUMING RATS

Confirmed high saccharin (HiS)-consuming and low saccharin (LoS)-consu ming rats were compared in their taste response to saccharin using a c ontinuous intraoral infusion procedure. On 2 separate days, rats were infused with 0.1% saccharin (rate = 1 ml/min) until they rejected flui d via passive drip or forceful fluid expulsion (at which time infusion was stopped for 30 s), and then again rejected fluid within 30 s afte r infusion was reinitiated. Two dependent measures were collected duri ng infusion procedures: latency to first fluid rejection and total inf usion time. On the first infusion day, HiS and LoS rats produced simil ar latencies to first rejection and total infusion times. However, HiS rats displayed significantly longer latencies to first rejection than LoS rats on the second infusion day. The results indicate that contin uous infusion procedures exposed differences between His and LoS lines , but only after an initial experience with saccharin, albeit a relati vely short exposure. The absence of immediate line differences with in fusion procedures suggests that preference differences for saccharin b etween HiS and LoS lines are not mediated by brainstem taste reflexes, but rather are guided by associative processes accomplished above the brainstem. Copyright (C) 1996 Elsevier Science Inc.