Traumatic brain injury (TBI) induces cachexia, hyper

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Abstracts / Frontiers in Neuroendocrinology 27 (2006) 91–94

Traumatic brain injury (TBI) induces cachexia, hyperthermia, and delayed neuronal damage. The adipokine leptin is implicated in the etiology of cachexia and may also possess neuroprotective properties. Another member of this family, FIAF, is increased during fasting and may also modulate angiogenesis. We previously demonstrated that: (a) leptin and FIAF are expressed in various regions of the brain, and (b) leptin protein levels are increased in brain following TBI. We hypothesized that TBI elevates leptin and FIAF mRNA levels as part of the brain’s response to injury. In the present study, adult male rats were subjected to a fluid percussion brain injury of moderate severity. Twelve hours post-injury rats were killed and ipsilateral and contralateral cerebral cortex (CTX), hippocampus (HIPPO), and thalamus (THAL) were dissected out for analysis. Following total RNA isolation, leptin (ob) and FIAF mRNA levels were measured in triplicate by TaqMan realtime RT-PCR. Ob gene expression was significantly elevated in the ipsilateral THAL (227%; p < 0.02) and CTX (255%; p < 0.0001) 12 h post-injury, but was only slightly increased in the ipsilateral HIPPO. Levels in the contralateral CTX, HIPPO, and THAL were unaffected. FIAF mRNA levels were markedly increased in the ipsilateral CTX (602%; p < 0.001), HIPPO (728%; p < 0.001), and THAL (484%; p < 0.01). However, unlike the changes in ob mRNA, FIAF gene expression was also upregulated in the contralateral CTX (188%; p < 0.01), HIPPO (255%; p < 0.01), and THAL (202%; p < 0.05) . These data suggest that gene expression changes in centrally derived leptin and FIAF are predominantly, but not exclusively, localized to the site of injury, and may play a role in local neuroprotection and angiogenesis. In addition, increases in brain-derived leptin could act via the hypothalamus to suppress appetite and increase weight loss, both of which are associated with TBI. Further investigations are required to clarify the mechanisms by which central adipokines promote altered metabolism and cell survival. (Funded by NSHRF, UIMRF/Capital Health, IWK, and NIH.) doi:10.1016/j.yfrne.2006.03.211

Analysis of GABAergic neurons in the medial preoptic nucleus and anteroventral periventricular nucleus of the guinea pig hypothalamus by single-cell RT-PCR Emma Coddington a, Jian Qiu a, Martin J. Kelly a, Oline K. Rønnekleiv a,b a Physiology and Pharmacology, Oregon Health and Science University, Portland, OR, USA

b

Oregon National Primate Research Center, Beaverton, OR, USA The mammalian hypothalamic–pituitary–gonadal axis is regulated at the level of the hypothalamus by estrogen, neuropeptides, and transmitters. GABAergic neurons are a target of estrogen feedback that is critical for controlling GnRH neurons. We have shown that estrogen attenuates the autoinhibition of GABAergic POA neurons during the initial LH suppressive phase and subsequently reduces GABAergic function during the LH surge [Wagner et al., J. Neurosci. (2001)]. Another hypothesis would place the site of positive feedback of estrogen at the level of the AVPV, where estrogen enhances the release of GnRH by action on Kisspeptin neurons [Han et al., J. Neurosci. (2005)]. The aim of this study was threefold: (1) to determine whether glutamic acid decarboxylase 65 (GAD65) co-localizes with signaling peptides in the MPN and AVPV of the guinea pig, (2) to determine the pattern of co-localization, and (3) to determine whether the co-localization pattern of transcripts is regulated by estrogen. To address these aims the contents of acutely dispersed cells were individually harvested from the MPN or AVPV from guinea pigs that were gonadectomized and injected with estrogen or oil (vehicle) and sacrificed 24 h later. Primers were designed using known guinea pig sequences (GAD65, GnRH) or by consensus sequence alignment using human and rodent sequence data. PCR product was confirmed by sequence analysis. Of the 42 cells harvested from the MPN (n = 6), 51% were positive for GAD65, indicating that approximately half of the harvested cells are GABAergic. The majority of GABAergic neurons (55%) express the mu opiate receptor transcript, which is consistent with our electrophysiological analysis of this region. Seven percent of the cells were positive for gonadotropin releasing hormone (GnRH), all of which express the transcript for mu opiate receptor. The co-localization of GnRH and mu opiate receptor is consistent with electrophysiology and in situ hybridization data [Lagrange et al., Endocrinol. (1995); Zeng et al., J. Comp. Neurol. (2005)]. Of the 41 cells harvested from the AVPV (n = 5), 63.5% were positive for GAD65, indicating that a higher proportion of harvested cells from this region compared to the larger MPN are GABAergic. Work is in progress to determine the cellular expression and modulation by estrogen of neurotransmitters and signaling molecules in AVPV and MPN neurons. (Supported by NIH Grants NS38809, NS43330, and DK68098.) doi:10.1016/j.yfrne.2006.03.212