Subepicardial plexus of the atria is an interdependent heart control system and its structure and function may be influenced by external factors. We studied the influence of protein deprivation on subepicardial neurons at early development stages by subjecting rats to a low protein diet (5% of casein) during pre and post natal period. Atrial neurons were identified by histochemical methods b-nicotinamide adenine dinucleotide (NADH) reaction, b-nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d) reaction and Acetylcholinesterase (AChE) reaction and counted in 21 day-old rats. Besides a significant reduction in body and heart weight, the total number of neurons decreased 46% in the undernourished group as compared to control animals. Our data suggest that deficient nutrition during early developmental period may produce irreversible deleterious changes later in life.