Mice Lacking Central Serotonergic Neurons Lost Their Sex Preference

Serotonin is an important neural transmitter that modulates many processes of the animal. We found that the mutant males which lacked serotoninergic neurons vigorously mounted other males. The mutant males emitted complex ultrasonic to both male and female, while the wild type mainly do it toward female. The mutant males lost mounting preference to female. The preference to male and female odor is also lost in the mutant males. But their social recognition and social memory is normal. Pharmacological deletion of serotonin using PCPA had similar phenotype. These means that the phenotype of the mutant male is not cause of a development problem or gene background. The taste and social approach is also preserved in the mutant mice. The results suggest that the serotonin in brain plays an important role in sex preference of male mice. The wild type mice pups emit multi ultrasonic vocalizations when they are separated from the mother. The similar ultrasonic vocalizations were reduced in pups lacking serotonergic neuron. The latencies of ultrasonic vocalization were similar in male mutant and wild type pups. But the latencies of ultrasonic vocalization in female mutant were longer than in the female wild type. The frequency of the ultrasonic vocalization was also higher in mutant pup than in wild type pup. The preference to the mother bedding was reduced in mutant pup than in wild type pup. These results indicate that serotonin play some roles in the pup emotion and the pup-mum attachment.