PEPTIDE YY AND THE Y-2 AGONIST PYY-(13-36) INHIBIT NEURONS OF THE DORSAL MOTOR NUCLEUS OF THE VAGUS

Peptide YY (PW) is released by endocrine cells in the ileum in respons e to the presence of fatty acids in the intestinal lumen. Circulating PYY suppresses vagally mediated digestive functions as a consequence o f direct action on neurons in the dorsal medulla. Recent evidence from our laboratory suggests that this PYY-mediated inhibition of digestio n occurs because of peptide action at the Y-2-type receptor in the dor sal medullary region encompassing vago-vagal reflex circuitry. The pre sent study describes the effects of PW and the specific Y-2 agonist pe ptide PYY-(13-36) on neurons of the dorsal motor nucleus of the vagus (DMN) in both the 1) intact in vivo and 2) in vitro brain stem slice p reparation. Our results show that 50% of DMN neurons recorded under in vivo or in vitro conditions, including synaptic blockade, are inhibit ed by the application of PYY or PYY-(13-36). Approximately 45% are not affected, and only similar to 5% are activated. These results suggest that one of the principal means by which PW suppresses digestive func tions is by the direct inhibition of cholinergic vagal efferent neuron s of the DMN via action at a Y-2 receptor.