Role of Central 5-Hydroxytryptamine Receptors in Micturition Control

5-Hydroxytryptamine (5-HT) receptors in the central nervous system have been implicated in the control of micturition. In rats and cats, spinal and supraspinal reflex pathways involved in lower urinary tract (LUT) function exhibit dense serotonergic innervation and multiple 5-HT receptors. At present, the most investigated 5-HT receptor that has been shown to play a role in the control of micturition is the 5-HT1A receptor, followed by 5-HT7, 5-HT2, and 5-HT3 receptors. Most studies focus on the effects of these receptors on the parasympathetic outflow to the bladder and the somatic outflow to the external urethral sphincter (EUS) in rats. Earlier studies have shown that the activation of 5-HT-containing brain areas (the raphe nuclei in the caudal brainstem) inhibits bladder activity. However, 5-HT1A and 5-HT7 receptors have recently been suggested to have an excitatory role in the control of bladder function. 5-HT1A receptors act at both a spinal and supraspinal level, while 5-HT7 receptors act only at a supraspinal level. The activation of 5-HT2A receptors in rats results in an increase in EUS activity. Overall, the pharmacological manipulation of the central serotonergic system can be a promising treatment strategy for LUT dysfunction. However, more studies are mandatory to fully understand the role of multiple 5-HT receptors in the control of LUT function.