Functional role of alpha1-adrenoceptors in the locus coeruleus: a microdialysis study.

The present study elucidates the role of alpha(1)-adrenoreceptors in the locus coeruleus (LC) using a dual-probe microdialysis in conscious rats. One probe sampled noradrenaline in the LC, whereas the second probe sampled noradrenaline in a main projection area, the prefrontal cortex (PFC). To investigate a possible tonic activation of LC neurons by alpha(1)-adrenoceptor, the alpha(1)-antagonist prazosin (10 microM) was infused into the LC.

Regulation of the release of serotonin in the dorsal raphe nucleus by alpha1 and alpha2 adrenoceptors.

To investigate the modulation of serotonin release in the dorsal raphe nucleus (DRN) by alpha(1) and alpha(2) adrenoceptors, dual-probe microdialysis was performed in conscious rats. The specific alpha(1) and alpha(2) adrenoceptor agonists and antagonists were locally infused into the DRN via retrograde microdialysis. The release of serotonin was simultaneously sampled from the DRN and prefrontal cortex (PFC).

The interaction between the locus coeruleus and dorsal raphe nucleus studied with dual-probe microdialysis.

The interaction between the locus coeruleus and dorsal raphe nucleus was investigated by means of dual-probe microdialysis in conscious rats. The release of noradrenaline and 5-hydroxytryptamine (5-HT) after inhibition or stimulation of locus coeruleus and dorsal raphe activity was sampled in both nuclei and analysed by high-pressure liquid chromatography (HPLC). The inhibition of locus coeruleus activity by the infusion of the alpha(2)-adrenoceptor agonist clonidine (100 microM) decreased the release of noradrenaline to 20% in the locus coeruleus and 30% in the dorsal raphe, whilst the release of 5-HT decreased to 80% of control in the two brain areas.