Receptor turnover and the action of 5-hydroxytryptamine on the salivary glands of the blowfly Calliphora erythrocephala, the housefly Musca domestica and frog skin epithelium.

Abstract

1. Continual stimulation of frog skin epithelium and the salivary glands of the insects Calliphora and Musca with 5-hydroxytryptamine (5-HT) leads to desensitisation, i.e. the tissue fails to respond to the application of further 5-HT. 2. Incubation of desensitised frog skin and Musca salivary glands with either N-acetyl neuraminic acid or inositol partially restored the 5-HT responses whilst incubation with a combination of N-acetyl neuraminic acid and inositol gave additive effects on the recovery of the 5-HT responses. 3. Incubation of desensitised salivary glands of Calliphora with inositol totally restored the 5-HT response whilst incubation with N-acetyl neuraminic acid had no effect. 4. It is concluded that desensitisation involves depletion of secondary messenger from the tissues coupled with receptor degradation and that considerable differences exist in the turnover of 5-HT receptors, the receptors in Musca salivary glands being highly labile, those in Calliphora salivary glands highly stable and those of frog skin epithelium being intermediate in their stability.