Pathways involved in micturition in the rat

Skidmore, Jennifer Ruth (1996) Pathways involved in micturition in the rat. University of Southampton, Doctoral Thesis.

Abstract

Within the dorsolateral pontine tegmentum, the nucleus locus coeruleus and the nucleus tegmentalis laterodorsalis have each been attributed with the role of the pontine micturition centre. These claims were investigated in rats by producing stereotaxically controlled electrolytic lesions in the region of locus coeruleus and the nucleus tegmentalis laterodorsalis and observing the effects of these lesions on bladder function. The methods of assessing bladder function included measurement of the bladder area from radiographs, measurement of urine volume and measurement of voiding threshold. The results of the first part of the study were inconclusive and an alternative method was developed, in which locus coeruleus was destroyed by administration of the chemical neurotoxin 6-hydroxydopamine. Since no effects on bladder function were observed locus coeruleus was precluded from a significant role in the control of normal micturition.

Further progress was made using a multitracer protocol enabling the multisynaptic micturition pathway to be traced in its entirety. Using this method, the pontine micturition centre was shown to be independent of both locus coeruleus and the nucleus tegmentalis laterodorsalis and to comprise a cluster of cells which correspond to Barrington's nucleus.

In addition to retrograde labelled neurons in the pons, anterogradely labelled nerve fibres, terminals/varicosities were observed in the major pelvic ganglion in association with bladder postganglionic neurons. Some of these terminals/varicosities were immunoreactive for somatostatin whilst others were immunoreactive for enkephalin, thereby implicating both somatostatin and enkephalin as neurotransmitters/neuromodulators within the micturition pathway.

It may be possible to extrapolate the knowledge obtained from investigation of the micturition pathway in rats to the clinical conditions observed in humans, particularly in association with bladder disorders following spinal cord injury, and to use this information to modify the management of these patients.

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