Summer Research Description: Although, the neurotransmitter serotonin (5-HT) is essential to brain and gastrointestinal tract development little is known about 5-HT signaling of autonomic and sensory neurons. The bladder and urethra receive autonomic innervation from both parasympathetic and sympathetic neurons, in which 5-HT receptor 3A (5-HT3A) is expressed. Mutations in 5-HT3A are associated with bladder dysfunction. Prior work in our lab suggests that mice without 5-HT3A have different proportions of adrenergic and cholinergic neurons innervating the bladder, compared to wild type mice. I hypothesize that proportions of other neuron types will also differ in bladders of 5-HT3A mutant mice. By utilizing a reverse transcription polymerase chain reaction (RT-PCR) and immunohistochemical approach, we are able to examine various neuronal markers: VIP, NET, NF200, nNOS, vAChT, and Ty3H at stage E14 in Htr3a-EGFP embryonic and postnatal day-2 mice. We will define patterns of normal gene expression at E14 and postnatal stages using 5-Htr3a-EGFP transgenic reporter mice, and then use this same approach in Htr3a knockout mice. I am analyzing the development of pelvic ganglia (PG) and the effect that 5-HT3A has on a variety of neuronal classes. Targeting these serotonin pathways and developmental changes may contribute to medicinal treatment and urinary dysfunction in similar disorders.