Somatosensory regulation of serotonin release in the central nucleus of the amygdala is mediated via corticotropin releasing factor and gamma-aminobutyric acid in the dorsal raphe nucleus

1. Intracellular recordings from neurons within dorsal raphe nucleus in slices from rat brain were used to study an inhibitory postsynaptic potential (IPSP) evoked by electrical stimulation. 2. The IPSP was observed in approximately 70% of neurons, had a latency to onset of 40-65 ms, reached a peak in 350-400 ms, had a total duration of 1-2 s, and reversed polarity at the potassium equilibrium potential. 3. This IPSP was blocked by spiperone (1 microM) and prolonged by fluoxetine (300 nM-30 microM) suggesting that it was mediated by 5-hydroxytryptamine (5-HT). 4. Superfusion with gamma-aminobutyric acid (GABA) and excitatory amino acid receptor antagonists were used to block "fast" synaptic potentials that preceded the IPSP such that it could be studied in isolation. Blockade of the GABA-mediated synaptic potentials increased the amplitude of the IPSP by 1.3-fold. The amplitude of the IPSP was reduced by 30% after blockade of the excitatory amino acid-mediated synaptic potential. 5. The results indicate that the IPSP recorded in dorsal raphe neurons was caused by 5-HT released at least in part from indirect (synaptically induced) excitation of 5-HT-containing cells within the slice.

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Inhibition of serotonin outflow by nociceptin/orphaninFQ in dorsal raphe nucleus slices from normal and stressed rats: Role of corticotropin releasing factor

Neurochemistry International ◽

10.1016/j.neuint.2009.01.004 ◽

2009 ◽

Vol 54 (5-6) ◽

pp. 378-384 ◽

Cited By ~ 17

Author(s):

Cristiano Nazzaro ◽

Silvia Marino ◽

Mario Barbieri ◽

Anna Siniscalchi

Keyword(s):

Dorsal Raphe Nucleus ◽

Dorsal Raphe ◽

Raphe Nucleus ◽

Corticotropin Releasing Factor ◽

Dorsal Raphé

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Effects of Acute or Chronic Administration of Anti-Migraine Drugs Sumatriptan and Zolmitriptan on Serotonin Synthesis in the Rat Brain

Cephalalgia ◽

10.1111/j.1468-2982.2004.00647.x ◽

2004 ◽

Vol 24 (1) ◽

pp. 2-11 ◽

Cited By ~ 59

Author(s):

CF Dobson ◽

Y Tohyama ◽

M Diksic ◽

E Hamel

Keyword(s):

Rat Brain ◽

Dorsal Raphe Nucleus ◽

Chronic Administration ◽

Brain Regions ◽

Dorsal Raphe ◽

Serotonin Release ◽

Raphe Nucleus ◽

Synthesis Rate ◽

Regional Effects ◽

Dorsal Raphé

Triptans are 5-HT1 receptor agonists used as anti-migraine drugs. They act primarily on meningeal blood vessels and on trigeminovascular afferents, but they may also exert central effects. We studied the regional effects of acute and chronic treatment with sumatriptan or zolmitriptan on the rate of serotonin (5-HT) synthesis in the rat brain, using the α-14C-methyl-L-tryptophan quantitative autoradiographic method. Sumatriptan at low (300 μg/kg, s.c.) and high (1 mg/kg) doses, as well as zolmitriptan (100 μg/kg), acutely decreased (15-40%, P < 0.05-0.001) 5-HT synthetic rate in many brain regions, including the dorsal raphe nucleus. Chronically, sumatriptan (21 days, approximately 300 μg/kg per day via osmotic minipumps) induced significant increases in the 5-HT synthesis rate in many projection areas but had no effect in the dorsal raphe nucleus. The acute effects on 5-HT synthesis rate would be compatible with activation of 5-HT1 autoreceptors that inhibit serotonin release. In contrast, the increased 5-HT synthesis rate observed after chronic sumatriptan might possibly result from a down-regulation/desensitization of 5-HT1 receptors and/or unmasking of excitatory triptan-sensitive 5-HT receptors. Overall, the present findings indicate that not only zolmitriptan but also sumatriptan affect brain serotonergic neurotransmission.

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