Sucrose intake and fasting glucose levels in 5-HT_1A and 5-HT_1B receptor mutant mice

Serotonin (5-HT)_1A and 5-HT_1B receptors have been implicated in the incidence and treatment of depression in part through the examination of animals lacking these receptors. Although these receptors have been repeatedly implicated in ingestive behavior there is little information about how 5-HT_1A and 5-HT_1B receptor mutant mice react to solutions of varying palatability. In the present experiment male and female 5-HT_1A and 5-HT_1B mutant and wild-type mice were presented with increasing concentrations of sucrose using a two-bottle choice procedure. In addition fasting blood glucose levels were assessed. Both male and female 5-HT_1B mutant mice drank more sucrose than WT mice but also consumed more water. Female, but not male, 5-HT_1A mutant mice similarly showed increased sucrose consumption, but did not demonstrate increased consumption of water. In addition, the pattern of increased sucrose consumption over genotype and sex was related to fasting blood glucose concentrations such that levels in male 5-HT_1B mutant mice were reduced relative to wild-type and 5-HT_1A mutant males, but similar to those of females. The findings in 5-HT_1B mutant mice emphasize the role of the 5-HT_1B receptor in regulating ingestive behavior, whereas female sex hormones and 5-HT_1A receptors may interact to alter sucrose consumption in 5-HT_1A mutant mice. In addition, these findings may have implications for the role of these receptors in the incidence and treatment of depression since the intake of sucrose has been used as an index of anhedonia in animal models of depression and antidepressant efficacy.