Intracisternal TRH analog induces Fos expression in gastric myenteric neurons and glia in conscious rats

Activation of gastric myenteric cells by intracisternal injection of the st able thyrotropin-releasing hormone (TRH) analog RX-77368, at a dose inducin g near maximal vagal cholinergic stimulation of gastric functions, was inve stigated in conscious rats. Fos immunoreactivity was assessed in gastric lo ngitudinal muscle-myenteric plexus whole mount preparations 90 min after in tracisternal injection. Fos-immunoreactive cells were rare in controls (sim ilar to1 cell/ganglion), whereas intracisternal RX-77368 (50 ng) increased the number to 24.8 +/- 1.8 and 26.8 +/- 2.2 cells/ganglion in the corpus an d antrum, respectively. Hexamethonium (20 mg/kg sc) prevented Fos expressio n by 90%, whereas atropine (2 mg/kg sc) had no effect. The neuronal marker protein gene product 9.5 and the glial markers S-100 and glial fibrillary a cidic proteins showed that RX-77368 induced Fos in both myenteric neurons a nd glia. Vesicular ACh transporter and calretinin were detected around the activated myenteric neurons. These results indicated that central vagal eff erent stimulation by intracisternal RX-77368 activates gastric myenteric ne urons as well as glial cells mainly through nicotinic ACh receptors in cons cious rats.