A ROLE FOR FYN TYROSINE KINASE IN THE SUCKLING BEHAVIOR OF NEONATAL MICE

NON-RECEPTOR-TYPE tyrosine kinases of the Src family, such as Src, Yes and Fyn, are strongly expressed in the brain and have been suggested to have an important function in the central nervous system1-5. We gen erated Fyn-deficient mice by inserting the beta-galactosidase gene (la cZ) into the fyn gene. The homozygous Fyn-mutant neonates from homozyg ous Fyn-deficient parents died because of a suckling problem. Neonates were, however, able to suckle milk normally when die homozygous mothe r's mammary glands had been activated by suckling of a heterozygous or wild-type pup. In these homozygous pups, the modified glomerular comp lex of the olfactory bulb, which had been suggested to play a role in perceiving pheromones, was abnormal in shape and reduced in size, and the hippocampal cell-layer was undulated. These results suggest that F yn may be involved in the initial step of instinctive suckling behavio ur in neonates.