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Delayed up-regulation of α-adrenoceptor populations in particular regions of the rat brain after stimulation of the nucleus locus coeruleus

Elsevier Ltd
Publication Date
DOI: 10.1016/0306-4522(86)90157-0
  • Biology
  • Pharmacology


Abstract We previously showed that electrical stimulation of the nucleus locus coeruleus resulted 4 weeks later in greatly improved performance in the acquisition and extinction of a food-reinforced operant task. To ascertain whether adrenergic receptors of particular brain regions were involved in this long term behavioral modification, we studied the characteristics of α 1, α 2 and β-binding sites after stimulation of the locus coeruleus. In the first experiment these characteristics were studied, 4 weeks after treatment, in cortex, hippocampus, hypothalamus and the brainstem. Neither the number, nor the affinity of β-receptors ([ 125I]iodocyanopindolol binding sites) was modified in any brain region. A significant increase in the number of α 1-receptors ([ 3H]prasozin binding sites) was observed in the cortex (62%). The number of α 2-receptors, ([ 3H]yohimbine binding sites), was significantly increased in cortex (99%), hippocampus (33%) and hypothalamus (113%). No significant alteration of the α 1, α 2 and β-adrenoceptors was observed in the brainstem. To investigate the time course of these adrenoceptor changes, the characteristics of α 1, α 2 and β-adrenoceptors were studied 2 weeks after stimulation using the same ligands and in the same brain regions. The only significant modifications observed were an increase of the α 2-adrenoceptors in the cortex (19.4%) and in the hypothalamus (54%). Furthermore, in both experiments, the increase in the number of α 1 and α 2-receptors was associated with a significant decrease in affinity. These results are discussed in relation to our previous behavioral and pharmacological findings.

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