A morphometric analysis of the autonomic innervation of cat tracheal glands

Quantitative methods have been used to examine the distribution of adrenergic and cholinergic axon varicosities to serous and mucous cells of cat tracheal glands. Cats were injected with 5-hydroxydopamine (5-OHDA) prior to removal of the trachea in order to fill adrenergic vesicles with intensely osmiophilic material. This facilitated the identification of adrenergic varicosities and provided a means by which they could be easily discriminated from cholinergic varicosities. Of all varicosities identified within 10 micrometer of the glands, 90% were cholinergic and 10% were adrenergic. Most of these varicosities were present in interstitial bundles located between acini. A small number of cholinergic varicosities, however, were located within 20 nm of acinar cells, forming close contact junctions. No differential innervation of serous and mucous cells was observed.