Tissue pressure in rat oral mucosa measured by micropuncture technique

Abstract

Tissue pressure or interstitial fluid pressure (IFP) was measured in 68 rats in different areas of the oral mucosa (free gingiva, attached gingiva in front and molars, alveolar mucosa, hard palate, cheek) by glass pipettes (diameter 2‐4 μm) connected to a servocontrolled counterpressure system. All the measurements of IFP were considerably above ambient pressure. The highest IFP was measured in the hard palate (14.8 mm Hg) and in attached gingiva (8.6, 9.2 mm Hg), while free gingiva, alveolar mucosa and cheek showed lower values (2.3, 3.6, 1.5 mm Hg respectively). Venous stasis resulted in an immediate rise in IFP in the attached gingiva. Repeated measurements of IFP at the same location gave the same results 3 h after induction of anesthesia, and there was no change in IFP in continuous recordings for up to 30 min. Administration of indomethacin did not change IFP. The results show that IFP in oral mucosa is high and that there is a marked regional variation in IFP, which may reflect regional differences in aspects of anatomy and function. The great difference between IFP in attached and free gingiva shows that there is a pressure gradient between these tissues, possibly maintained by the anatomical structure and the drainage of gingival fluid into the gingival sulcus.