The effect of pro-inflammatory cytokines on the discharge rate of vagal nerve paraganglia in the rat.
Bottom Line: Twenty-three successful single fibre recordings were obtained from 10 animals.IL-1 beta and TNF-alpha had no statistically significant effect on the frequency of action potentials observed (p=0.39 and 0.42, respectively, repeated measures ANOVA).In conclusion, an immune role for SLN paraganglia has not been established.
Affiliation: School of Medicine and Medical Science, Health Sciences Centre, University College Dublin, Belfield, Dublin 4, Ireland.Show MeSH
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Mentions: One of the SLNs was located and dissected free, to include its bifurcation, an area known to contain a large density of glomus tissue (Fig. 1). The nerve was then transferred to an organ bath containing warm (37 °C) HEPES-buffered Tyrode's solution (Sigma code: T2145; containing in mM NaCl 137.0, KCl 2.7, MgCl2 1.0, CaCl2 1.36, Na2HPO4 0.35, (d)-glucose 5.5, HEPES 10, at pH 7.4). The experimental set-up is depicted in Fig. 2. In brief, the peripheral end of the nerve was placed in flexible polyvinyl chloride tubing (outer diameter: 5 mm; inner diameter: 3 mm) – via a small perforation/narrow opening created with a scalpel – with the proximal end exposed to the bath milieu and the bifurcation (with glomi) suspended in the lumen of the tube. Care was taken to avoid damaging the tissue and a seal was maintained by the elastic recoil of the tube and bolstered with Vaseline. The rubber tubing was superfused at 1–2 ml/min with HEPES-buffered Tyrode's solution via two reservoirs; both contained heated HEPES-buffered Tyrode's solution. O2 or N2 were bubbled through the first reservoir and IL-1β, TNF-α or CN added to the second reservoir according to experimental protocols. The reservoirs fed the tube by gravity and were connected via a three-way tap to a single inflow tube ensuring a constant and equal flow rate from both reservoirs. The of the superfusate was measured continuously with a probe (World Precision Instruments; OXEL-1 ISO2) and in later experiments and temperature were measured continuously using an oxylite 2000 system (Oxford optronix). It proved important to ensure that the fluid in the tubing dead space (which lost heat and gases) was filled with warm solution immediately before each trial. The effect of perfusing the preparation with stagnant cool solution can be seen in Fig. 4, where the first CN perfusion causes a transient dip in the recording. The subsequent CN tests are less affected because the solution in the tubing more closely approximates the reservoir solution.
Affiliation: School of Medicine and Medical Science, Health Sciences Centre, University College Dublin, Belfield, Dublin 4, Ireland.