Aging alters in a region-specific manner serotonin transporter sites and 5-HT(1A) receptor-G protein interactions in hamster brain |
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Authors: | Duncan Marilyn J Hensler Julie G |
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Institution: | Department of Anatomy and Neurobiology, University of Kentucky Medical Center, 800 Rose Street, Lexington, KY 40536-0298, USA. mjdunc0@pop.uky.edu |
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Abstract: | Key proteins regulating serotonergic activity, specifically the serotonin transporter and 5-HT(1A) receptor, were examined in the midbrain raphe nuclei of young (3-4 months) and old (17-19 months) hamsters (N=7-10/group). An age-related decrease in the maximal density of serotonin transporter sites labelled with (3)H]paroxetine (fmol/mg protein, Old: 396+/-13; Young: 487+/-27) was observed in the dorsal raphe nucleus (DRN) but not the median raphe nucleus (MRN), without affecting the affinity of (3)H]paroxetine. In the DRN and MRN, the stimulation of (35)S]GTP gamma S binding by the 5-HT(1A) receptor agonist 8-OH-DPAT, or the number of 5-HT(1A) receptor sites labeled with (3)H] MPPF, was not different in old versus young animals. Thus in the DRN, aging decreased serotonin transporter sites without changing 5-HT(1A) receptor activation of G proteins or 5-HT(1A) receptor density. In the CA(1) region of hippocampus, 8-OH-DPAT-stimulated (35)S]GTP gamma S binding was increased in the older animals (% above basal, Old: 141+/-21; Young: 81+/-17) without changing specific (3)H] MPPF binding sites, suggesting that the capacity of 5-HT(1A) receptors to activate G proteins is enhanced. Aging also appears to enhance this capacity in the dentate gyrus, because this region exhibited a constant level of 8-OH-DPAT-stimulated (35)S]GTP gamma S binding in spite of an age-related decrease in the number of (3)H] MPPF binding sites (fmol/mg protein, Old: 203+/-21; Young: 429+/-51). |
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Keywords: | Dorsal raphe nucleus Median raphe nucleus Hippocampus Dentate gyrus CA1 [35S]GTPγS binding [3H]paroxetine binding [3H]MPPF binding Autoradiography |
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