Experimental induction of premature movement of rat palatal shelves in vivo.

In order to enhance further knowledge of palatal shelf movement and the factors involved in palate closure, a method was developed for prematurely elevating palatal shelves in utero. Approximately 7 hours before expected shelf elevation, pregnant Sprague-Dawley rats were laparotomized and two medially directed squeezes were applied to the face of some of the embryos through the intact uterine wall. Palates from control (unsqueezed) and experimental animals were obtained immediately after the procedure and 2, 4, 7, 12 and 24 hours later. In the 0, 2 and 4 hours groups, 82% of experimental palates were elevated, whereas only 6% of control palates were elevated. At 0 hours only the hard palate in the experimental group had elevated, but at 2 and 4 hours almost half this group showed elevation of the soft palate as well, and, in addition, contact had been made between the elevated shelves.