[Effect of nalbuphine on external pancreatic secretion in rats]

Pancreatic secretion is controlled by neural and endocrine mechanisms. The administration of 2-desoxyglucose (2DG) to rats stimulates pancreatic secretion through a mainly vagal pathway, and provides an useful pharmacological model to study the agents (especially opiates and adrenergic drugs) which can modulate this neural pathway. In the present study, basal and 2DG-stimulated pancreatic secretion were measured in anesthetized rats. Nalbuphine had no effect on basal secretion; it antagonized 2DG-induced pancreatic stimulation in a dose-related fashion between 0.5 and 15 mg/kg iv. The effect of nalbuphine was suppressed by naloxone, but not by alpha and beta-adrenoceptor blocking agents, indicating an essentially opiate effect. In order to test whether an inhibition of kappa receptors participates in the nalbuphine effect, centrally or peripherally acting kappa agonists were associated with nalbuphine. Neither U50488H, nor ICI204448 changed 2DG stimulation and nalbuphine effect. In conclusion, the effect of nalbuphine on 2DG-stimulated pancreatic secretion was similar to that of methadone and buprenorphine, required larger doses, and seemed to mainly involve mu receptors.