Delayed up-regulation of alpha-adrenoceptor populations in particular regions of the rat brain after stimulation of the nucleus locus coeruleus.
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 alpha 1, and alpha 2 and beta-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 beta-receptors ([125I]iodocyanopindolol binding sites) was modified in any brain region. A significant increase in the number of alpha 1-receptors ([3H]prazosin binding sites) was observed in the cortex (62%). The number of alpha 2-receptors, ([3H]yohimbine binding sites), was significantly increased in cortex (99%), hippocampus (33%) and hypothalamus (113%). No significant alteration of the alpha 1, alpha 2 and beta-adrenoceptors was observed in the brainstem. To investigate the time course of these adrenoceptor changes, the characteristics of alpha 1, alpha 2 and beta-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 alpha 2-adrenoceptors in the cortex (19.4%) and in the hypothalamus (54%). Furthermore, in both experiments, the increase in the number of alpha 1 and alpha 2-receptors was associated with a significant decrease in affinity. These results are discussed in relation to our previous behavioral and pharmacological findings.
D000818:Animals; D001933:Brain Stem / Q000502:physiology; D002540:Cerebral Cortex / Q000502:physiology; D004558:Electric Stimulation; D006624:Hippocampus / Q000502:physiology; D007031:Hypothalamus / Q000502:physiology; D020120:Iodocyanopindolol; D008125:Locus Coeruleus / Q000502:physiology*; D008297:Male; D010869:Pindolol / Q000031:analogs & derivatives / Q000378:metabolism; D011224:Prazosin / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D011942:Receptors, Adrenergic, alpha / Q000502:physiology*; D015016:Yohimbine / Q000378:metabolism
D011942:Receptors, Adrenergic, alpha; D015016:Yohimbine; D020120:Iodocyanopindolol; D010869:Pindolol; D011224:Prazosin