EFFECT OF PANCREATIC-POLYPEPTIDE ON RAT DORSAL VAGAL COMPLEX NEURONS

1. Pancreatic polypeptide (PP) microinjected into the dorsal vagal com plex (DVC) elevates gastric activity through a vagal mechanism. Thus, it was hypothesized that PP alters the activity of nuclei comprising t he DVC, i.e. the nucleus tractus solitarii (NTS) and the dorsal motor nucleus (DMN). 2. In vivo and in vitro approaches were used. For in vi vo studies, micropipettes were used for recording and injecting vehicl e or PP. Neurons were identified as NTS or DMN using orthodromic and a ntidromic activation, respectively, following vagal stimulation. Gastr ic-related DVC neurons were located using antral inflation. For in vit ro studies, DMN neurons were recorded from medullary slices. 3. Of the twenty-eight NTS and DMN neurons identified, fifteen were activated, six inhibited and seven unaffected after PP microinjection. Forty-two gastric-related neurons were located in the DVC, of which twenty-five were stimulated by PP and seventeen exhibited no change. No gastric-re lated cells were inhibited. 4. For in vitro studies, 66% of DMN neuron s were activated by PP (n = 27/47) while the remaining 33% mere inhibi ted (n = 14/47). Similar results were obtained in normal or synaptic b lockade media. 5. These results support the hypothesis that PP alters DVC neuronal activity, which may thereby lead to the previously observ ed alterations in gastric activity.