The release of noradrenaline in the locus coeruleus and prefrontal cortex studied with dual-probe microdialysis

The present study was undertaken to investigate and compare the properties of noradrenaline release in the locus coeruleus (LC) and prefrontal cortex (PFC). For that aim the dual-probe microdialysis technique was applied for simultaneous detection of noradrenaline levels in the LC and PFC in conscio us rats. Calcium omission in the LC decreased noradrenaline levels in the L C, but increased its levels in the PFC. Novelty increased noradrenaline lev els in both structures. Infusion of the az-adrenoceptor agonist clonidine d ecreased extracellular noradrenaline in the LC as well as in the PFC. Infus ion of the alpha (2A)-adrenoceptor antagonist BRL44408, or the alpha (1)-ad renoceptor agonist cirazoline into the LC or PFC caused a similar dose-depe ndent increase in both structures. When BRL44408 or cirazoline were infused into the LC. few effects were seen in the PFC. Infusion of the 5-HT1A-rece ptor agonist flesinoxan into the LC or the PFC decreased the release of nor adrenaline in both structures. When flesinoxan was infused into the LC. no effects were seen in the PFC. When the GABA(A) antagonist bicuculline was a pplied to the LC, noradrenaline increased in the LC as well as in the PFC. It is concluded that the release of noradrenaline from somatodendritic site s and nerve terminals responded in a similar manner to presynaptic receptor modulation. The possible existence of dendritic noradrenaline release is d iscussed. (C) 2001 Elsevier Science B.V. All rights reserved.