Age‐Related Changes in Rat Serotonergic and Adrenergic Systems and in Receptor Responsiveness to Subchronic Desipramine Treatment

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Abstract
Noradrenergic (NA) and serotonergic (5‐HT) receptor profiles were compared in the cerebral cortex of young adult (3 months old) and aged (24 months old) male Sprague Dawley rats. β and α‐1 receptors were significantly decreased in 24 month old rats, whereas α‐2 receptors remained unchanged. 5‐HT‐2 Postsynaptic receptors and 5‐HT high affinity uptake were reduced in aged animals; on the other hand the number of3H‐imipramine (3H‐IMI) recognition sites located on serotonin nerve terminals and labelled also by3H‐paroxetine (3H‐PAR), were significantly higher in the cerebral cortex of old rats. The ratio 5‐hydroxyindoleacetic acid (5‐HIAA)/5‐HT, an index of serotonin turn‐over, increased in some brain areas of senescent rats. There were no age‐related changes in the responsiveness of investigated binding sites to subchronic desipramine treatment; the density of β‐noradrenergic and 5‐HT‐2 serotonergic receptors and that of3H‐IMI binding sites was reduced both in young adult and aged rats.
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