Antibody to Thy-1 antigen injected into rat hypothalamus selectively inhibits carbamyl choline induced drinking

Abstract

The Thy-1 differentiation antigen on the cell surfaces of mouse and rat thymocytes, lymphocytes^1–4, epidermis⁵, developing skeletal muscle⁶, and brain^1,3,4 has not yet been assigned a function. In rat and mouse brain, Thy-1 reaches adult levels at about 3 weeks of age from minimal or variably low levels at birth^3,7–9. In vitro studies of fetal or newborn cerebellar neurons have shown that granule cells and some large multipolar cells become Thy-1 positive during culture^10,11. All dorsal root ganglion neurones in culture express Thy-1^11,12. The antigen appears to be enriched in synaptosomal fractions^13,14 but Thy-1 has recently been demonstrated on the surface and dendrites of microdissected neurons of adult rat brain¹⁵. In the brain Thy-1 has been thought to be a neuronal antigen, but some cerebellar astrocytes become Thy-1 positive after prolonged culture¹⁶. The transient or developed occurrence of the Thy-1 glycoprotein on selected cell surfaces would suggest that it mediates an event associated either with differentiation or with a differentiated function. The recent report by Dulbecco et al. that monoclonal hybridoma antibody against Thy-1.1 (aThy-1.1) blocks a differentiation event in culture of a rat mammary carcinoma cell line¹⁷ is, the first demonstration of a functional link between the molecule and a specific developmental process. We consider brain Thy-1 to be a differentiated adult expression, however, and we report here that injecting antibody to Thy-1 antigen into the rat hypothalamus caused selective inhibition of carbamyl choline induced drinking.