Postnatal development of nitrergic neurons in the myenteric plexus of rat stomach

The effect of age on the proportion of nicotinamide adenine dinucleotide ph osphate diaphorase (NADPHd)-positive neurons was investigated in the myente ric plexus of five different gastric areas of 1-day-, 1-week-, 2-week-, 1-m onth- and 2-month-old rats. Protein gene product 9.5 immunocytochemistry wa s used as a marker for the total enteric neuron population in order to esta blish the percentage of gastric nitrergic neurons in relation to age. The p ercentage of NADPHd-positive neurons in the proximal parts of the rat stoma ch (34-38%) is significantly higher than in the antral part (29%). This dif ference persists in all the age groups investigated. No significant relativ e increase with age of NADPHd-positive neurons could be observed in any of the areas studied. These findings imply that the increased nitrergic respon se in the rat proximal stomach as seen in pharmacological studies cannot be explained by an increased relative number of nitrergic neurons.