Effect of central administration of serotoninergic agonists on electrolyte excretion control

1. The participation of different central serotoninergic (5HT) receptors in the mediation of Na+ excretion (UNaV), K+ excretion (UKV) and urine output (UV) was evaluated. 2. Male Wistar rats weighing 220-280 g were used in each group of 9-18 animals. The rats were injected intracerebroventricularly (icv) with the 5HT agonists MK212 (1.5, 15.0 and 30.0 micrograms), 8-OH-DPAT (5.0 and 15.0 micrograms), 5HT (2.5, 12.5 and 25.0 micrograms) and DOI (10.0 and 25.0 micrograms). 3. At the lowest MK212 dose, UNaV was significantly reduced (0.18 +/- 0.04 microEq/min vs 0.35 +/- 0.04 microEq/min for saline) at 20 min. At the highest dose, MK212 provoked a significant increase in UNaV (0.60 +/- 0.06 microEq/min vs 0.34 +/- 0.03 microEq/min for saline) at 40 min. UKV values were significantly modified only at the 1.5-micrograms dose (0.18 +/- 0.04 microEq/min vs 0.35 +/- 0.04 microEq/min for saline) at 20 min. 4. Icv injection of 8-OH-DPAT provoked a significant reduction in UNaV (0.16 +/- 0.05 microEq/min vs 0.35 +/- 0.03 microEq/min for saline) and UKV (0.15 +/- 0.05 microEq/min vs 0.34 +/- 0.02 microEq/min for saline) at 40 min both doses. 5. Icv injection of 5HT at the highest dose provoked a significant increase in UNaV (0.92 +/- 0.10 microEq/min vs 0.33 +/- 0.04 microEq/min for saline) and in UKV (0.55 +/- 0.08 microEq/min vs 0.24 +/- 0.07 microEq/min for saline) at 40 min. 6. Icv administration of DOI caused a natriuretic response (0.69 +/- 0.12 microEq/min vs 0.31 +/- 0.04 microEq/min for saline) at 40 min, with no significant effect on UKV.(ABSTRACT TRUNCATED AT 250 WORDS)