Atchley Deann P D, Weaver Karen L, Eckel Lisa A
Department of Psychology and Program in Neuroscience Florida State University, Tallahassee, FL 32306-1270, USA.
Physiol Behav. 2005 Oct 15;86(3):265-71. doi: 10.1016/j.physbeh.2005.08.001.
Meal size is decreased during the estrous stage of the rat's ovarian reproductive cycle. This is mediated, in part, by estradiol's ability to increase the strength by which negative-feedback signals function to inhibit meal size. For example, we recently reported that the anorectic effect of fenfluramine, a serotonin agonist, is enhanced during estrus. Here, we investigated whether a decrease in the strength of positive-feedback signals, like those related to the taste of food, contributes to the decrease in meal size observed either in estrous rats or following fenfluramine treatment. Rats were given brief access to six sucrose solutions (0.0, 0.025, 0.05, 0.1, 0.2, and 0.4 M) and the mean number of licks to these solutions was monitored in diestrous and estrous rats treated with 1 mg/kg fenfluramine or saline vehicle. Following saline treatment, estrous rats displayed fewer licks than diestrous rats to the 0.025 M sucrose solution. Following fenfluramine treatment, a decrease in the number of licks to 3 of the 5 sucrose solutions was observed in diestrous rats only. This decrease in sucrose palatability was limited to brief access tests, as overnight preference for the 0.025 M sucrose solution was not decreased by fenfluramine in either diestrous or estrous rats. Our findings suggest that estrous rats experience a decrease in the strength of positive-feedback signals elicited by a dilute sucrose solution and that the anorectic effect of fenfluramine is associated with a decline in positive-feedback signaling in the diestrous rat.
在大鼠卵巢生殖周期的发情期，进食量会减少。这部分是由雌二醇增强负反馈信号抑制进食量的能力介导的。例如，我们最近报道，血清素激动剂芬氟拉明的厌食作用在发情期会增强。在此，我们研究了与食物味道相关的正反馈信号强度降低是否导致发情期大鼠或芬氟拉明处理后出现的进食量减少。给大鼠短暂接触六种蔗糖溶液（0.0、0.025、0.05、0.1、0.2和0.4 M），并监测用1 mg/kg芬氟拉明或生理盐水处理的动情间期和发情期大鼠对这些溶液的平均舔舐次数。生理盐水处理后，发情期大鼠对0.025 M蔗糖溶液的舔舐次数少于动情间期大鼠。芬氟拉明处理后，仅在动情间期大鼠中观察到对5种蔗糖溶液中的3种的舔舐次数减少。蔗糖适口性的这种降低仅限于短暂接触试验，因为在动情间期或发情期大鼠中，芬氟拉明均未降低对0.025 M蔗糖溶液的过夜偏好。我们的研究结果表明，发情期大鼠由稀释蔗糖溶液引发的正反馈信号强度降低，并且芬氟拉明的厌食作用与动情间期大鼠正反馈信号的下降有关。
