Maturation of Micturition-Related Neural Circuits That Control Pelvic Visceromotor Functions in Postnatal Rats

Abstract

Pelvic visceromotor functions such as micturition are regulated by coordinated autonomic and somatic motor pathways from the central nervous system. The parasympathetic system induces detrusor muscle contraction while the somatic system facilitates relaxation of the external urethral sphincter, ensuring synchronized and efficient bladder emptying during the voiding process. This study explores the relationship between Barrington's nucleus corticotropin-releasing hormone (CRH)-ergic projections and the formation of perineural nets (PNNs) among spinal motoneurons, particularly parasympathetic preganglionic neurons in the intermediolateral nucleus (IML) and Onuf's nucleus during the maturation of the neural circuitry controlling pelvic visceromotor functions. Immunohistochemical analysis revealed CRH expression commenced at postnatal Day 5 (P5) in both the IML and Onuf's nucleus, progressively increasing with age. By P60, CRH expression in Onuf's nucleus showed significant sexual dimorphism, higher in males than in females. In contrast, PNN formation exhibited distinct sex-dependent temporal patterns: Males showed earlier formation in the IML at P25, while females exhibited earlier PNN appearance in Onuf's nucleus at P25. Notably, delayed and reduced formation of PNN compared to somatic motoneurons in previous studies suggests an extended period of synaptic plasticity. This finding suggests a potentially longer and more effective recovery period for pelvic visceromotor system compared to the locomotor system. Furthermore, the observed sex difference in CRH expression and PNN formation in Onuf's nucleus may indicate the involvement of sex hormones. These results contribute to understanding the mechanism and treatment approaches tailored to age, sex, and the recovery of specific function such as micturition following spinal cord injury.