Lesions of the Dorsomedial Hypothalamic Nucleus Do Not Influence the Daily Profile of Pineal Metabolism in Rats

Mota, S R; Canteras, Newton S.; Bartol, I; Skorupa, A L; Scialfa, Julieta Helena; Terra, Ilza Mingarini; Afeche, Solange Castro; Cipolla‐Neto, José

doi:10.1159/000054628

Cited by 5 publications

(4 citation statements)

References 24 publications

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“…Unlike behavioral and corticosteroid rhythms, melatonin and Tb circadian rhythms do not seem to be critically dependent on the DMH. DMH lesions did not affect the circadian rhythm of serum melatonin, consistent with a previous cell-specific lesion study (Mota et al, 2001) and previous hypotheses that the SCN drives melatonin circadian rhythms via direct projections to the PVH (Klein et al, 1983;Vrang et al, 1995). DMH lesions reduced the CI and cosinor amplitudes of Tb by only 25-33%, much less than the effects on NREM and REM sleep rhythms.…”

Section: Discussionsupporting

confidence: 90%

Critical Role of Dorsomedial Hypothalamic Nucleus in a Wide Range of Behavioral Circadian Rhythms

et al. 2003

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The suprachiasmatic nucleus (SCN) contains the brain's circadian pacemaker, but mechanisms by which it controls circadian rhythms of sleep and related behaviors are poorly understood. Previous anatomic evidence has implicated the dorsomedial hypothalamic nucleus (DMH) in circadian control of sleep, but this hypothesis remains untested. We now show that excitotoxic lesions of the DMH reduce circadian rhythms of wakefulness, feeding, locomotor activity, and serum corticosteroid levels by 78-89% while also reducing their overall daily levels. We also show that the DMH receives both direct and indirect SCN inputs and sends a mainly GABAergic projection to the sleep-promoting ventrolateral preoptic nucleus, and a mainly glutamate-thyrotropin-releasing hormone projection to the wake-promoting lateral hypothalamic area, including orexin (hypocretin) neurons. Through these pathways, the DMH may influence a wide range of behavioral circadian rhythms.

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Section: Discussionsupporting

confidence: 90%

Critical Role of Dorsomedial Hypothalamic Nucleus in a Wide Range of Behavioral Circadian Rhythms

et al. 2003

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“…It is unlikely that the persistence of oestrous cycles in MBHx females is due to disruption of melatonin secretory activity. The dorsomedial hypothalamus does not participate in neural control of the pineal gland; ablation of this structure neither affects the circadian rhythm of melatonin production nor the inhibition of pineal melatonin metabolism by light (28, 29). Furthermore, male MBHx hamsters infused with short‐day melatonin signals fail to undergo gonadal involution, thereby supporting the notion that the absence of an adequate short‐day melatonin signal is not responsible for the continuation of reproduction in MBHx hamsters (10).…”

Section: Discussionmentioning

confidence: 99%

Photoperiodic Control of Oestrous Cycles in Syrian Hamsters: Mediation by the Mediobasal Hypothalamus

Lewis¹,

Freeman²,

Dark³

et al. 2002

J Neuroendocrinology

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To assess whether the mediobasal hypothalamus (MBH) is necessary for photoperiodic control of oestrous cycles and prolactin secretion, we tested intact female Syrian hamsters (controls) and those that had sustained unilateral or bilateral lesions of the MBH. All hamsters displayed 4-day oestrous cycles postoperatively in the long-day photoperiod (14 h light/day); control females and those with unilateral MBH damage ceased to undergo oestrous cycles approximately 8 weeks after transfer to a short-day photocycle (10 h light/day), whereas 12 of 15 females with bilateral MBH lesions continued to generate 4-day oestrous cycles throughout 22 weeks in short days. Serum prolactin concentrations were either undetectable or low in all hamsters 8 or 14 weeks after the transfer to short-day lengths, but increased above long-day baseline values by week 22. We conclude that melatonin-binding sites in the MBH mediate suppression of oestrous cycles but not prolactin secretion by short-day lengths; recovery of prolactin secretion in females during prolonged exposure to short-day lengths reflects development of refractoriness to melatonin in a substrate distinct from the MBH. These findings suggest that separate neural pathways mediate photoperiodic control of gonadotropin and prolactin secretion in female hamsters.

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“…The pineal glands were removed and kept at −70°C for later determination of their melatonin content. Melatonin was assayed by high‐performance liquid chromatography as previously described [17]. Briefly, each gland was sonicated in a solution of perchloric acid, 0.02% ethylenediaminetetraacetic acid (EDTA) and 0.02% sodium disulfide, centrifuged, and the clear supernatant was injected (20 μ L loop) into the chromatographic system (Waters, Milford, MA, USA) using 30% methanol in acetate buffer as the mobile phase.…”

Section: Chromatographic Detection Of Melatoninmentioning

confidence: 99%

Calorie restriction reduces pinealectomy‐induced insulin resistance by improving GLUT4 gene expression and its translocation to the plasma membrane

Zanquetta

Seraphim

Sumida

et al. 2003

Journal of Pineal Research

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The present study aimed to investigate insulin sensitivity and GLUT4 expression protein in pinealectomized rats, as well as to determining the effects of melatonin and calorie restriction on the changes induced by pinealectomy. Wistar rats were pinealectomized (Pinx) or sham operated (Sham), and studied 30 days later. Melatonin replacement treatment (50 g/100 g body weight) was continued for 30 days after pinealectomy. Calorie restriction was performed by offering 60% of the standard food intake. In vivo insulin sensitivity was evaluated using the glucose disappearance constant (kITT) during an insulin tolerance test, and GLUT4 mRNA and protein were assessed by Northern and Western blotting, respectively. The in vitro effect of melatonin on GLUT4 protein content in plasma membrane was investigated in adipocytes isolated from intact rats. Compared with Sham rats, Pinx rats showed decreased kITT (40%), GLUT4 expression in white adipose tissue (WAT, approximately 70%), and unchanged GLUT4 expression in skeletal muscle. Melatonin treatment in Pinx rats restored the kITT and GLUT4 protein to control values. No in vitro effects of melatonin (10-9 m) upon GLUT4 protein were observed. Calorie restriction of Pinx rats increased their kITT value ( approximately 40%), total GLUT4 protein content ( approximately 240%) and its translocation to the plasma membrane ( approximately 80%) in WAT. The results show that pinealectomy, for lack of melatonin, decreased insulin sensitivity as well as GLUT4 gene expression. Calorie restriction improved insulin sensitivity in Pinx rats, and this was related to increased GLUT4 gene expression and insulin-induced GLUT4 translocation to the plasma membrane in WAT.

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Lesions of the Dorsomedial Hypothalamic Nucleus Do Not Influence the Daily Profile of Pineal Metabolism in Rats

Cited by 5 publications

References 24 publications

Critical Role of Dorsomedial Hypothalamic Nucleus in a Wide Range of Behavioral Circadian Rhythms

Critical Role of Dorsomedial Hypothalamic Nucleus in a Wide Range of Behavioral Circadian Rhythms

Photoperiodic Control of Oestrous Cycles in Syrian Hamsters: Mediation by the Mediobasal Hypothalamus

Calorie restriction reduces pinealectomy‐induced insulin resistance by improving GLUT4 gene expression and its translocation to the plasma membrane

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