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A putative flip-flop switch for control of REM sleep.
Lu J, Sherman D, Devor M, Saper CB (2006) A putative flip-flop switch for control of REM sleep. Nature 441(1):589-594. doi: 10.1038/nature04767
Summary: The authors propose a REM sleep regulatory system that involves GABAergic and glutaminergic neurons in the mesopontine tegmentum. Among other work, 2 µl of 0.1% orexin-SAP (Cat. #IT-20) was injected into the medial medullary reticular formation of rats. This work suggests the sharp transitions into and out of REM sleep are controlled by reciprocal interactions between GABAergic REM-off and REM-on neuronal populations.
Related Products: Orexin-B-SAP (Cat. #IT-20)
Estradiol and orexin-2 saporin actions on multiple forms of behavioral arousal in female mice.
Easton A, Dwyer E, Pfaff DW (2006) Estradiol and orexin-2 saporin actions on multiple forms of behavioral arousal in female mice. Behav Neurosci 120(1):1-9. doi: 10.1037/0735-7044.120.1.1
Summary: Many aspects of female behavioral arousal in response to estrogens are not yet well understood. Here the authors examine the role of orexins as targets for estrogens. Female mice were treated with 10 ng of orexin-SAP (Cat. #IT-20) into each hemisphere of the lateral hypothalamus. The mice were then tested in different modes of behavioral arousal. Mice treated with orexin-SAP displayed decreases in sensory responsiveness and fearfulness concomitant with a reduction in orexin cell number.
Related Products: Orexin-B-SAP (Cat. #IT-20)
Orexin lesions block food-related increases in cortical acetylcholine release
Fadel J, Frederick-Duus D, Butts R (2005) Orexin lesions block food-related increases in cortical acetylcholine release. Neuroscience 2005 Abstracts 644.8. Society for Neuroscience, Washington, DC.
Summary: Hypothalamic orexin (hypocretin) neurons influence and coordinate arousal, state-dependent behavior, feeding and metabolic processes. Orexin fibers are seen in close proximity to choline acetyltransferase (ChAT)-positive magnocellular somata in portions of the basal forebrain and intrabasalis administration of orexin A increases cortical acetylcholine (ACh) release, suggesting that orexin inputs to the basal forebrain may be important for biasing attentional resources toward stimuli related to underlying homeostatic challenges. Here, we mildly food-deprived rats and trained them to associate an environmental stimulus (darkness) with presentation of palatable food. Microdialysis in these animals showed that the darkness stimulus, with or without accompanying food presentation, produced a robust increase in cortical ACh release. A subset of animals received unilateral administration of the immunotoxin orexin B-saporin (OxB-SAP; 350 ng/0.5 μl) or vehicle into the lateral hypothalamus and perifornical area. OxB-SAP produced a substantial (70-80%) ipsilateral loss of orexin-immunoreactive cells and a corresponding decrease in orexin fiber density in the basal forebrain. OxB-SAP did not alter the number or basal forebrain neurons showing ChAT-immunoreactivity and produced only mild (approximately 15%) loss of melanin-concentrating hormone cells. Basal cortical ACh release was unaffected in lesioned animals, but OxB-SAP lesions abolished increases in cortical ACh release associated with the food-paired stimulus. These data indicate that orexin inputs to the basal forebrain are required for food anticipatory-related increases in cortical ACh release. Orexins appear to be important components of the neural pathways by which interoceptive cues related to homeostasis recruit forebrain attentional systems.
Related Products: Orexin-B-SAP (Cat. #IT-20)
Hypocretin/orexin neurons and the perifornical hypothalamus play a more important role in contextual fear than in restraint stress
Furlong TM, Carrive P (2005) Hypocretin/orexin neurons and the perifornical hypothalamus play a more important role in contextual fear than in restraint stress. Neuroscience 2005 Abstracts 304.11. Society for Neuroscience, Washington, DC.
Summary: We investigated the role of the neuropeptide hypocretin (Hcrt; also known as orexin) in two different types of stress: conditioned fear to context and restraint stress. For contextual fear, male Wistar rats were tested by re-exposure to a chamber where electric footshocks had previously been administered. For restraint stress, the rats were restrained in tight Plexiglas tubes. In the first study, lesions of the perifornical region of the hypothalamus (PeF; where Hcrt neurons are located) were made with a Hcrt-saporin toxin prior to testing. The cardiovascular response was measured using radio-telemetry. The pressor and tachycardic responses to the context were reduced by 77% and 74% respectively, compared to an intact group (p<0.001, for both comparisons). The lesioned group also displayed significant reductions in freezing (by 67%) and ultrasonic vocalisations (by 74%). In contrast, the cardiovascular response to restraint stress did not differ between the two groups (p>0.5). In the second study, two hours after the tests, the rats were euthanased (200 mg/kg sodium pentobarbitone, i.p) and their brains removed and processed for double immunohistochemical detection of Hcrt and Fos. There was a higher percentage of Hcrt neurons double labeled with Fos after contextual fear (17%) than after restraint stress (6%), which indicates that more Hcrt neurons were active during contextual fear (p=0.024). These studies suggest that the PeF region and Hcrt neurons play a more important role in contextual fear than in restraint stress.
Related Products: Orexin-B-SAP (Cat. #IT-20)
Adenosine levels do not increase with 6 h waking in rats with lesions of the lateral hypothalamus
Gerashchenko D, Murillo-Rodriguez E, Blanco-Centurion C, Lin L, Nishino S, Mignot E, Shiromani PJ (2005) Adenosine levels do not increase with 6 h waking in rats with lesions of the lateral hypothalamus. Neuroscience 2005 Abstracts 63.9. Society for Neuroscience, Washington, DC.
Summary: The hypocretin neurons in the lateral hypothalamus (LH) have been implicated in wakefulness, but it is not clear which projection is responsible for the arousal. One possibility is that the LH neurons induce wakefulness by driving the basal forebrain (BF) wake-active neurons (Gerashchenko and Shiromani, Cellular & Molec Neurosci, 29: 41, 2004). Here we measure adenosine (AD) levels in the BF as a marker of arousal and test the LH-BF circuit in Sprague-Dawley rats with lesions of the LH induced by hypocretin-2-saporin. 64 days after lesions the rats were kept awake (gentle handling) for six hours (ZT 3-9) and microdialysis samples (5ul) were collected hourly for 9 hours (24h after probe stabilization). AD levels were assessed using HPLC. Hypocretin-saporin ablated 95% of the hypocretin neurons and reduced CSF hypocretin levels (-75% versus control). AD levels increased with 6h waking in saline control rats (n=9), consistent with previous studies in cats (Strecker et al., Behav Brain Res 115: 183, 2000) and rats (Murillo-Rodriguez et al., Neuroscience 123: 361, 2004). However, in rats with LH lesions (n=5) such an increase with waking did not occur. Sleep drive was measured by conducting a rodent version of a multiple sleep latency test (MSLT). In this test, conducted over 10h (from ZT2-ZT12) the rats were kept awake for 20min and then allowed 20min to sleep. The lesioned rats had more sleep during the 20min sleep periods indicating a higher sleep drive. These results suggest that in narcolepsy when the HCRT LH neurons die, there is a loss of stimulation of the wake-active BF neurons and the decline in this pathway may be the cause of the increased sleep attacks. Supported by VA Medical Research and NIH
Related Products: Orexin-B-SAP (Cat. #IT-20)
Insomnia following hypocretin2-saporin lesions of the substantia nigra.
Gerashchenko D, Blanco-Centurion CA, Miller JD, Shiromani PJ (2006) Insomnia following hypocretin2-saporin lesions of the substantia nigra. Neuroscience 137(1):29-36. doi: 10.1016/j.neuroscience.2005.08.088
Objective: To investigate which regions of major arousal areas might be responsible for the changes in sleep-wake architecture
Summary: It is known that orexin (also known as hypocretin) is involved in waking. The results suggest that motor activity is under inhibitory control of the substantia nigra.
Usage: Bilateral injection of Orexin-SAP (92 and 184 ng/ml, 0.25 ml in the ventral tegmental area and 0.5 ml in the substantia nigra) of rats induced insomnia, as well as hyperactivity and stereotypic movements.
Related Products: Orexin-B-SAP (Cat. #IT-20)
Featured Article: Effects of intraseptal orexin-saporin on spatial memory
Pang K, Smith H (2005) Featured Article: Effects of intraseptal orexin-saporin on spatial memory. Targeting Trends 6(4)
Related Products: Orexin-B-SAP (Cat. #IT-20)
Read the featured article in Targeting Trends.
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Orexin-saporin lesions of the medial septum impair spatial memory.
Smith HR, Pang KC (2005) Orexin-saporin lesions of the medial septum impair spatial memory. Neuroscience 132(2):261-271. doi: 10.1016/j.neuroscience.2004.12.037
Summary: The medial septum and diagonal band of Broca (MSDB) have been shown to be important for spatial learning and memory. The authors investigated the role orexin-containing neurons from the hypothalamus play in these processes. Rats were treated with three injections of 40-120 ng of orexin-SAP (Cat. #IT-20) into the MSDB. Performance in spatial working and spatial reference memory tasks indicate that orexin innvervation of the MSDB may modulate spatial memory through both GABAergic and cholinergic septohippocampal neurons.
Related Products: Orexin-B-SAP (Cat. #IT-20)
Effects of lesions of the histaminergic tuberomammillary nucleus on spontaneous sleep in rats.
Gerashchenko D, Chou TC, Blanco-Centurion CA, Saper CB, Shiromani PJ (2004) Effects of lesions of the histaminergic tuberomammillary nucleus on spontaneous sleep in rats. Sleep 27(7):1275-1281. doi: 10.1093/sleep/27.7.1275
Summary: Although evidence suggests that histaminergic neurons in the tuberomammillary nucleus (TMN) promote wakefulness, this has not been investigated using specific lesioning agents. In this study, the authors utilize the fact that TMN neurons express the orexin-B receptor by eliminating these neurons with an injection of 50 ng of orexin-SAP (Cat. #IT-20) into the posterior hypothalamus. The data indicate that histaminergic neurons are not required for the homeostatic regulation of sleep.
Related Products: Orexin-B-SAP (Cat. #IT-20)
Effects of hypocretin2-saporin and antidopamine-beta-hydroxylase-saporin neurotoxic lesions of the dorsolateral pons on sleep and muscle tone.
Blanco-Centurion C, Gerashchenko D, Salin-Pascual RJ, Shiromani PJ (2004) Effects of hypocretin2-saporin and antidopamine-beta-hydroxylase-saporin neurotoxic lesions of the dorsolateral pons on sleep and muscle tone. Eur J Neurosci 19(10):2741-2752. doi: 10.1111/j.0953-816X.2004.03366.x
Summary: Narcolepsy is linked to the loss of orexin (or hypocretin)-containing neurons in the brain. These neurons are located in the perifornical region of the posterior hypothalamus and innervate the locus coeruleus (LC). To investigate the role of the LC in sleep the authors injected 0.3 µl of 192-Saporin (Cat. IT-01) or anti-DBH-SAP (Cat. #IT-03) at 1 µg/µl. They also used 0.3 µl of orexin-SAP (Cat. #IT-20) at either 90 ng/µl or 60 ng/µl in a separate group of animals. The results indicate that orexin innervation to the pons plays a role in arousal from sleep.
Related Products: 192-IgG-SAP (Cat. #IT-01), Anti-DBH-SAP (Cat. #IT-03), Orexin-B-SAP (Cat. #IT-20)