Epidermal growth factor has both growth-promoting and growth-inhibiting effects on physical and neurobehavioral development of neonatal mice.

The protein molecule epidermal growth factor (EGF) exerts powerful effects on mouse physical development, since repeated subcutaneous administrations of murine EGF (3.5 mg/kg, from postnatal day 2 to postnatal day 10) cause precocious eyelid opening (as early as day 8 instead of day 13 in control littermates receiving 3.5 mg/kg cytochrome c) and precocious eruption of the lower incisors (day 6 instead of day 8). By contrast, the same EGF treatment retards both the rate of body growth and the full appearance of several neurobehavioral signs of maturation, such as righting and grasping responses. Neonatal mice receiving 5 mg/kg murine nerve growth factor (NGF) under the same treatment schedule, although showing a significant retardation in body weight gain, exhibited only limited changes in neurobehavioral maturation. Specifically, the appearance of slow and swift righting, response to strong tactile stimulation, hindlimb and forelimb grasping, pole grasping, and vertical screen and screen climbing were significantly retarded by EGF and slightly advanced by NGF (the only significant NGF effect was an acceleration of swift righting maturation). Polypeptide growth factors seem to play an important role in physical and neurobehavioral development of altricial rodents, orchestrating the relative maturation of different tissutal targets on different developmental stages.