Pentagastrin on neurotransmitter enzyme activities in the rat gastrointestinal tract

The effects of three doses (5, 100, and 250 μg/kg) of pentagastrin on the activities of choline acetyltransferase (ChAT) and acetylcholine esterase (AChE), the neurotransmitter enzymes that synthesize and degrade acetylcholine, and monoamine oxidase (MAO), the degradation enzyme for catecholamines, were investigated. Enzyme activities were assayed in 6 gastrointestinal segments of 21- and 28-day-old and adult rats. All animals were injected intraperitoneally for 7 days with pentagastrin, and the results were compared with age-matched controls receiving saline for 7 days. Plasma and adrenal corticosterone levels were measured. No consistent differences in adrenocortical variables existed between pentagastrin- and saline-treated animals. Similarly, no consistent pentagastrin dose responses of ChAT, AChE, and MAO activities were evident. However, at the highest dose pentagastrin generally produced increases in ChAT activities in 21- and 28-day-old rats, while producing decreases in AChE and MAO activities in 21-day-old rats and increases in 28-day-old animals. There were few significant differences in enzyme activities in adult rats receiving pentagastrin as compared to saline.