Circadian variation in sensitivity of suprachiasmatic and lateral geniculate neurones to 5‐hydroxytryptamine in the rat.

Mason, Robert J.

doi:10.1113/jphysiol.1986.sp016172

Cited by 104 publications

(30 citation statements)

References 35 publications

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“…Thus, the extent of phase-shifting response could be influenced by postsynaptic, as well as by presynaptic, 5-HT-related actions, with the extent of a shift being determined by the circadian period of delivery of the nonphotic stimulus, as well as by the pattern of 5-HT release preceding the stimulus. Although a relationship between physiological change in 5-HT release and postsynaptic responsiveness to 5-HT has received little study, it is suggested that circadian fluctuations in postsynaptic neurophysiological and behavioral responses to 8-OH-DPAT (Mason, 1986;Currie and Coscina, 1993;Lu and Nagayama, 1996) may be keyed to rhythmic daily changes in 5-HT release modulating daily changes in 5-HT 1A receptor sensitivity.…”

Section: Discussionmentioning

confidence: 99%

In VivoResetting of the Hamster Circadian Clock by 5-HT₇Receptors in the Suprachiasmatic Nucleus

2001

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Serotonin (5-HT) has been strongly implicated in the regulation of the mammalian circadian clock located in the suprachiasmatic nuclei (SCN); however, its role in behavioral (nonphotic) circadian phase resetting remains elusive. Central to this issue are divergent lines of evidence that the SCN may, or may not, be a target for the phase-resetting effects of 5-HT. We have addressed this question using a novel reverse-microdialysis approach for timed perfusions of serotonergic and other agents to the Syrian hamster SCN with durations equivalent to the increases in in vivo 5-HT release during phase-resetting behavioral manipulations. We found that 3 hr perfusions of the SCN with either 5-HT or the 5-HT 1A,7 receptor agonist 2-dipropylamino-8-hydroxy-1,2,3,4-tetrahydro-naphthalene (8-OH-DPAT) at midday advanced the phase of the free-running circadian rhythm of wheel-running assessed using an Aschoff type II procedure. Phase shifts induced by 8-OH-DPAT were enhanced more than threefold by pretreatment with the 5-HT synthesis inhibitor para-chlorophenylalanine. Phase advances induced by SCN 8-OH-DPAT perfusion were significantly inhibited by the 5-HT 2,7 receptor antagonist ritanserin and by the more selective 5-HT 7 receptor antagonist DR4004, implicating the 5-HT 7 receptor in mediating this phase resetting. Concurrent exposure to light during the 8-OH-DPAT perfusion abolished the phase advances. Furthermore, coperfusion of the SCN with TTX, which blocked in vivo 5-HT release, did not suppress intra-SCN 8-OH-DPAT-induced phase advances. These results indicate that 5-HT 7 receptor-mediated phase resetting in the SCN is markedly influenced by the degree of postsynaptic responsiveness to 5-HT and by photic stimulation. Finally, 5-HT may act directly on SCN clock cells to induce in vivo nonphotic phase resetting.

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Section: Discussionmentioning

confidence: 99%

In VivoResetting of the Hamster Circadian Clock by 5-HT₇Receptors in the Suprachiasmatic Nucleus

2001

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“…Interestingly, SCN neurons in brain slices show a circadian variation in sensitivity to serotonin in terms of firing rate, such that the neurons are more sensitive to inhibition of firing rate by serotonin in the subjective night (Mason, 1986). Besides the circadian rhythm of sensitivity to serotonin, the SCN also display a circadian rhythm in recovery from serotonin.…”

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confidence: 99%

“…Besides the circadian rhythm of sensitivity to serotonin, the SCN also display a circadian rhythm in recovery from serotonin. Mason (1986) demonstrated that the time of recovery after inhibition of neuronal activity was longer when serotonin was administered during the day-time than during the night.…”

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confidence: 99%

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Serotonin regulates the phase of the rat suprachiasmatic circadian pacemaker in vitro only during the subjective day.

Medanic

Gillette

1992

The Journal of Physiology

151

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SUMMARY1. The suprachiasmatic nucleus (SCN) of the hypothalamus is the primary pacemaker for circadian rhythms in mammals. The 24 h pacemaker is endogenous to the SCN and persists for multiple cycles in the suprachiasmatic brain slice.2. While serotonin is not endogenous to the SCN, a major midbrain hypothalamic afferent pathway is serotonergic. Within this tract the dorsal raphe nucleus sends direct projections to the ventrolateral portions of the SCN. We investigated a possible regulatory role for serotonin in the mammalian circadian system by examining its effect, when applied at projection sites, on the circadian rhythm of neuronal activity in rat SCN in vitro.3. Eight-week-old male rats from our inbred colony, housed on a 12 h light: 12 h dark schedule, were used. Hypothalamic brain slices containing the paired SCN were prepared in the day and maintained in glucose and bicarbonate-supplemented balanced salt solution for up to 53 h. 4. A 1011 ml drop of 10-6 M-serotonin (5-hydroxytryptamine (5-HT) creatinine sulphate complex) in medium was applied to the ventrolateral portion of one of the SCN for 5 min on the first day in vitro. The effect of the treatment at each of seven time points across the circadian cycle was examined. The rhythm of spontaneous neuronal activity was recorded extracellularly on the second and third days in vitro. Phase shifts were determined by comparing the time-of-peak of neuronal activity in serotonin-vs. media-treated slices.5. Application of serotonin during the subjective day induced significant advances in the phase of the electrical activity rhythm (n = 11). The most sensitive time of treatment was CT 7 (circadian time 7 is 7 h after 'lights on' in the animal colony), when a 70 + 0-1 h phase advance was observed (n = 3). This phase advance was perpetuated on day 3 in vitro without decrement. Serotonin treatment during the subjective night had no effect on the timing of the electrical activity rhythm (n= 9).6. The specificity of the serotonin-induced phase change was assessed by treating t To whom correspondence should be addressed. MS 9615M. MEDANIC AND M. U. GILLETTE slices in the same manner with a microdrop of serotonergic agonists, 5-carboxamidotryptamine, that targets the 5-HT1 class of receptors, or 8-hydroxydipropylaminotetralin (8-OH DPAT), that acts on the 5-HTlA receptor subtype. Daytime (CT 9) application of 5-carboxamidotryptamine resulted in a 6-0+001 h phase advance (n = 3), while treatment during the subjective night (CT 15, n = 2) had little observable effect. Similarly, treatment with 8-OH DPAT at CT 9 induced a phase advance of 69 + 01 h (n = 3) in the rhythm of electrical activity.7. These results demonstrate that serotonin can induce large phase changes in the SCN circadian pacemaker and that the SCN undergoes endogenous changes in sensitivity to serotonin. The data suggest that serotonergic inputs to the ventrolateral SCN can regulate the circadian pacemaker during the daytime.

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“…Subsequent modulatory effects of BTS 54 505 on agonist-evoked responses were then routinely assessed using agonist ejection currents that elicited 50-80% maximal response. Electrophysiological recording, display and processing of discriminated signals was conventional (Mason, 1986). Discriminated neuronal activity was plotted as integrated firing rate histograms over successive 5 s epochs onto a chart recorder.…”

Section: Methodsmentioning

confidence: 99%

The effects of BTS 54 505, a metabolite of sibutramine, on monoamine and excitatory amino acid‐evoked responses in the rat dorsolateral geniculate nucleus in vivo

Scott

Luscombe²,

Mason

1994

British J Pharmacology

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1 The effects of BTS 54 505, the primary amine metabolite of the non-tricyclic putative antidepressant sibutramine, on the responses evoked by visual stimulation and ionophoretic application of noradrenaline (NA), 5-hydroxytryptamine (5-HT) and excitatory amino acids (EAAs) in the rat dorsolateral geniculate nucleus (dLGN) have been investigated. 2 Ionophoretic application of 5-HT to dLGN neurones attenuated visually-evoked (n = 46), NMDAevoked (n = 21) and AMPA-evoked responses (n = 21), while ionophoretic application of NA potentiated visually-evoked activity in these cells (n = 27). 3 Simultaneous application of BTS 54 505 with 5-HT (over 120 s) resulted in a prolongation of the recovery time (i.e. the period required by a neurone to recover by 50%, RT50) from the 5-HT-mediated suppression of discharge activity (,275% increase in RTm,). BTS 54 505 also prolonged the recovery time from a NA-mediated potentiation of firing (;450% increase in RTm). These effects on recovery time are attributed to the inhibition of uptake of both 5-HT and NA by BTS 54 505. The amplitude of the response to 5-HT or NA was unaffected by co-ejection of BTS 54 505. 4 Ionophoretic application of N-methyl-D-aspartate (NMDA) produced a current-dependent increase in neuronal firing, as did application of the non-N4DA receptor agonist a-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA). A simultaneous 120 s application of BTS 54 505 inhibited the NMDA response in all cells studied (mean EDm = 16 ± 5 nA) but had no effect on AMPA-evoked activity in the majority of the same cells (n = 15/21). 5 Short 10 s applications of BTS 54 505, at ejecting currents () 30 nA) that attenuated NMDA-evoked activity in all cells studied, had no effect on either response amplitude or recovery time from ionophoretic application of 5-HT, suggesting that inhibition of NMDA-evoked activity by BTS 54 505 was not mediated by 5-HT uptake blockade. 6 These results suggest that BTS 54 505 inhibits NMDA-evoked activity, and the observation that this effect is unlikely to be due to raised levels of endogenous 5-HT following monoamine uptake blockade indicate that BTS 54 505 may interact directly with the NMDA receptor ionophore complex.

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Circadian variation in sensitivity of suprachiasmatic and lateral geniculate neurones to 5‐hydroxytryptamine in the rat.

Cited by 104 publications

References 35 publications

In VivoResetting of the Hamster Circadian Clock by 5-HT₇Receptors in the Suprachiasmatic Nucleus

In VivoResetting of the Hamster Circadian Clock by 5-HT₇Receptors in the Suprachiasmatic Nucleus

Serotonin regulates the phase of the rat suprachiasmatic circadian pacemaker in vitro only during the subjective day.

The effects of BTS 54 505, a metabolite of sibutramine, on monoamine and excitatory amino acid‐evoked responses in the rat dorsolateral geniculate nucleus in vivo

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Circadian variation in sensitivity of suprachiasmatic and lateral geniculate neurones to 5‐hydroxytryptamine in the rat.

Cited by 104 publications

References 35 publications

In VivoResetting of the Hamster Circadian Clock by 5-HT7Receptors in the Suprachiasmatic Nucleus

In VivoResetting of the Hamster Circadian Clock by 5-HT7Receptors in the Suprachiasmatic Nucleus

Serotonin regulates the phase of the rat suprachiasmatic circadian pacemaker in vitro only during the subjective day.

The effects of BTS 54 505, a metabolite of sibutramine, on monoamine and excitatory amino acid‐evoked responses in the rat dorsolateral geniculate nucleus in vivo

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Product

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In VivoResetting of the Hamster Circadian Clock by 5-HT₇Receptors in the Suprachiasmatic Nucleus

In VivoResetting of the Hamster Circadian Clock by 5-HT₇Receptors in the Suprachiasmatic Nucleus