Effect of norepinephrine receptors on trigeminal rhythm generation in newborn rats

N-methyl-D,L-aspartate acid and bicuculline are required to enhance the tri geminal rhythmic activities in an in vitro isolated brainstem block prepara tion. In this study, we analyzed the effect of norepinephrine on the trigem inal neural circuit underlying rhythmic jaw movements. Rhythmic trigeminal activity is observed in brainstem preparations (inferior colliculus to obex ) only following blockade of cu,adrenoceptors with idazoxan. This observati on, combined with the inhibition of rhythm by alpha (2)-adrenoceptor agonis ts suggests endogenous alpha (2)-adrenoceptor mediated inhibition of trigem inal networks. A complex noradrenergic modulation of trigeminal systems is further supported by the prazosinsensitive potentiation of rhythm by bath a pplication of the alpha (1)-adrenoceptor agonist phenylephrine. (C) 2000 El sevier Science Inc.