Loading…
Activation of unmyelinated afferent fibres by mechanical stimuli and inflammation of the urinary bladder in the cat
1. We examined the functional properties of unmyelinated primary afferent neurones innervating the pelvic viscera in twenty-five anaesthetized cats. The axons were isolated from the intact dorsal root and the intact or chronically de-efferented ventral root of the segment S2. All units were electric...
Saved in:
Published in: | The Journal of physiology 1990-06, Vol.425 (1), p.545-562 |
---|---|
Main Authors: | , , |
Format: | Article |
Language: | English |
Subjects: | |
Citations: | Items that cite this one |
Online Access: | Get full text |
Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
Summary: | 1. We examined the functional properties of unmyelinated primary afferent neurones innervating the pelvic viscera in twenty-five
anaesthetized cats. The axons were isolated from the intact dorsal root and the intact or chronically de-efferented ventral
root of the segment S2. All units were electrically identified with electrical stimulation of the pelvic nerve. 2. The responses
of the neurones were studied with natural stimulation of the urinary bladder using innocuous and noxious increases of intravesical
pressure and at the onset of an acute artificial inflammation induced by intraluminal injection of mustard or turpentine oil.
3. Out of 297 unmyelinated afferent units isolated from the dorsal root, seven were excited by an increase of the intravesical
pressure during contractions and distension of the urinary bladder. These units were silent when the bladder was empty and
had thresholds of 30-50 mmHg which are presumed to be noxious. Further increases of the intravesical pressure were accurately
encoded by the discharge rate of the fibres. Out of sixty-eight unmyelinated afferent units isolated from the ventral root
none was activated by these stimuli. 4. Intraluminal injection of mustard oil excited mechanosensitive units at short latency.
The discharge was not closely related to changes of the intravesical pressure and the units displayed on-going activity after
the irritant had been removed. This observation suggests that the units had also chemosensitive properties and that the receptive
endings were located in the bladder wall. 5. In sixteen cats ninety-five afferent fibres that were not activated by noxious
mechanical stimuli of the urinary bladder were systematically tested with intraluminal injections of mustard oil. This excited
7/67 dorsal root units and 4/28 ventral root units with short latency. Intraluminal application of turpentine oil, tested
on twenty-six afferents in four animals, did not produce a rapid excitation. 6. Following the induction of an inflammation
some previously non-mechanosensitive units started to respond to changes of intravesical pressure in the biologically relevant
pressure range of the urinary bladder. 7. In conclusion, a small subpopulation (2.4%) of unmyelinated visceral afferents responds
to high, presumably noxious, intravesical pressure and intraluminal application of chemical irritants. Acute inflammation
excites a larger proportion of afferents (9.5%) that are not activated by acute noxious mechanical stimu |
---|---|
ISSN: | 0022-3751 1469-7793 |
DOI: | 10.1113/jphysiol.1990.sp018117 |