Projections and neurochemistry of interneurones in the myenteric plexus ofthe guinea-pig gastric corpus

Recently, motor neurones of the myenteric plexus innervating the muscle lay ers or the mucosa have been identified in the guinea-pig stomach. We applie d the neuronal tracer Dil (1,1'-didodecyl-3,3,3',3'-tetramethylindocarbocya nine perchlorat) onto myenteric ganglia in order to identify populations of interneurones in the myenteric plexus of the guinea-pig stomach. The traci ng was combined with the immunohistochemical detection of calbindinD28k (CA LB), choline acetyltransferase (ChAT), neuropeptide Y (NPY) and 5-hydroxytr yptamine (serotonin) (5-HT) and the results were compared to the neurochemi cal coding of target specific motor neurones. Long projecting (similar to5. 4 mm) ChAT/CALB/+/-5-HT-, nitric oxide synthase (NOS)/CALB- and short proje cting (similar to1.1 mm) ChAT/NPY-neurones were identified as descending in terneurones. CALB positive ascending interneurones contained ChAT but rarel y 5-HT (code: ChAT/CALB). This study identified ascending and descending in terneurones in the gastric myenteric plexus and revealed the neurochemical coding of some of the interneurone populations. (C) 2000 Elsevier Science I reland Ltd. All rights reserved.