Elsevier

Neuroscience Letters

Volume 189, Issue 2, 14 April 1995, Pages 65-68
Neuroscience Letters

Presynaptic displacement of serotonin by α-methyl-5-hydroxytryptamine in the nucleus tractus solitarius of the rat

https://doi.org/10.1016/0304-3940(95)11450-BGet rights and content

Abstract

Rat brain slices containing the nucleus tractus solitarius loaded with [3H]5-hydroxytryptamine ([3H]5-HT) for superfusion were stimulated at (3 Hz, 25 mA, 1 min) resulting in fractional release ratios S2S1 of 0.89 for [3H]5-HT in the presence of the serotonin uptake inhibitor 1.0 μM 6-nitroquipazine (6-NQ). α-Methylserotonin (α-Me-5-HT; 1.0 μM), a non-selective 5-HT1 and 5-HT2 receptor agonist, significantly reduced the S2S1 ratio of [3H]5-HT without affecting the basal release ratios B2B1 1.00 ± 0.04. Without 6-NQ in the perfusion medium 1.0 μM α-Me-5-HT sharply increased the basal release B2B1 to 2.21 (P < 0.01). In low Ca2+ medium the S2S1 ratio was reduced to 0.06 and α-Me-5-HT promoted a B2B1 release of 2.17 (P < 0.01). The 5-HT3 antagonist LY-278,584 did not block α-Me-5-HT induced basal release of [3H]5-HT. Both pindolol and LY-53,857 blocked the autoinhibitory effects of α-Me-5-HT, but only LY-53,857 and 6-NQ blocked the basal release induced by α-Me-5-HT. These results suggest that α-Me-5-HT reduces neurotransmitter release through the serotonin autoreceptor and displaces serotonin through a non-exocytotic release mechanism.

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Cited by (4)

This work was supported by grants from: NIMH (MH 47181 and MH 17153), NIH (GM-08167), NSF (HRD 9104797).

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