Vagally mediated stimulation of gastric acid secretion by intravenously administered adenosine derivatives in anaesthetized rats.

The effects of adenosine and some of its analogues on gastric acid secretion were investigated in rats. These compounds increased gastric acid secretion in anaesthetized rats after intravenous injection, the order of potency being 5'-N-ethylcarboxamidoadenosine (NECA) greater than (-)N6-phenylisopropyladenosine (L-PIA), N6-cyclohexyladenosine (CHA) greater than (+)N6-phenylisopropyladenosine (D-PIA) greater than 2-chloroadenosine (2-CADO) greater than adenosine (ADO). The stimulation of acid secretion by L-PIA in anaesthetized rats was antagonized by theophylline and 8-phenyltheophylline and totally prevented by vagotomy and atropine. Intracerebroventricular administration of L-PIA had no effect on gastric acid secretion in anaesthetized rats, whereas in conscious rats it inhibited the output of acid, pepsin and fluid. These results indicate that adenosine derivatives stimulate gastric acid secretion in anaesthetized rats by activating the vagus nerve via adenosine receptors in afferent pathways.