Nasal passages, sensory

Alarie, Y. and Luo, J.E. (1986). Sensory irritation by airborne chemicals A basis to establish acceptable levels of exposure. In Toxicology of the Nasal Passages (Barrow, C.S., Ed.). Hemisphere, New York, pp. 91-100. 

The olfactory region located in the poorly accessible recessed roof of the nasal passages offers the potential for certain compounds to circumvent the blood-brain barrier and enter into the brain [48]. The olfactory sensory cells are in contact with both the nasal cavity and the CNS and this neuronal connection constitutes a direct pathway to the brain. By utilizing this pathway drugs would not only circumvent the blood-brain barrier, but also avoid any hepatic first-pass effect and degradation in the blood compartment, a particularly important issue in the case of peptide drugs. 

Buckley and coworkers (1985) have investigated the inhalation toxicity of dimethy-lamine in F-344 rats and B6C3F1 mice. Animals exposed to 175 ppm for 6 h/day, 5 days/week for 12 months showed significant lesions in the nasal passages. Rats developed more extensive olfactory lesions than did mice. The study indicated that olfactory sensory cells were highly sensitive to dimethylamine. Even at a concentration of 10 ppm, the current threshold limit value, the rodents developed minor lesions from exposure. 

This is followed by conjunctivitis, inflammation of the mucous membranes of the nose, larynx, and respiratory passages, coryza (inflammation of the mucous membranes), mild tracheobronchitis, skin lesions, and perforation of the nasal septum. The final phase includes symptoms of peripheral neuritis, primarily sensory in nature. Depressant effects on bone marrow with disturbances of both erythropoiesis and myelopoiesis have also been reported (Sittig 1985). 

Larval Arizona tiger salamanders (Ambystoma tigrinum nebulosum) can discriminate between kin and nonkin (Pfennig et al. 1994). In experimental tests, cannibalistic morphs may prey preferentially on unrelated individuals over related ones. The sensory basis for this discrimination was examined by covering the nares of test animals with Vetbond (3M Animal Care Products), an w-butyl cyanoacrylate tissue adhesive. This material blocks the passage of water over the nasal epithelium. In tests, some animals had their nares blocked, while sham controls had the adhesive placed between their nares. Larvae whose nares were blocked consumed kin and nonkin randomly. Animals without their nares blocked consumed more nonkin than kin. These results suggest that discrimination is based on chemical cues. 

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