Effects of corticosterone ingestion on hippocampal [(3)H]serotonin reuptake in inbred rat strains
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OBJECTIVE: There is evidence for a regulatory impact of corticoids on hippocampal serotonergic systems, including serotonin (5-HT) synthesis and 5-HT(1A) receptor expression and/or activity. On the other hand, contradictory data have emerged as to the regulation of the 5-HT transporter by corticoids. Using male Spontaneously Hypertensive Rats (SHRs) and Wistar-Kyoto (WKY) rats, we have analysed whether subchronic corticosterone alters in a strain-dependent manner the reuptake activity of the hippocampal 5-HT transporter. METHODS: Two separate experiments were performed. In the first experiments, we assessed the impact of corticosterone ingestion (400 microg/ml in drinking water for 7 days) on hippocampal reuptake of increasing concentrations of [(3)H]5-HT (6.25-100 nM). In the second series of experiments, we measured whether such a corticosterone regimen affected the potency of the antidepressant citalopram to block the reuptake of 10 nM of [3H]5-HT. RESULTS: Corticosterone administration, which markedly reduced body weight gains and adrenal weights in both strains, increased Km and Vmax values in SHRs but decreased these values in WKY rats, compared to vehicle (2.4 % ethanol) administration. In addition, it was observed that neither the basal reuptake of 10 nM [(3)H]5-HT nor the potency of citalopram to block selectively such a reuptake (IC(50) = 2.88-3.63 nM) differed between vehicle- and corticosterone-treated animals. CONCLUSION: Under our experimental conditions, both the reuptake of a physiological concentration of 5-HT and the potency of an antidepressant to inhibit such a reuptake proved insensitive to repeated corticosterone administration.