Neuroscience
-
Comparative Study
Photoperiod differentially regulates clock genes' expression in the suprachiasmatic nucleus of Syrian hamster.
The suprachiasmatic nuclei (SCN) contain the master circadian pacemaker in mammals. Generation and maintenance of circadian oscillations involve clock genes which interact to form transcriptional/translational loops and constitute the molecular basis of the clock. There is some evidence that the SCN clock can integrate variations in day length, i.e. photoperiod. ⋯ Bmal1 expression is phase advanced without a change of duration in SP compared with LP. Furthermore, the expression of Clock is rhythmic under SP whereas no rhythm is observed under LP. These results, which provide further evidence that the core clock mechanisms of the SCN integrate photoperiod, are discussed in the context of the existing molecular model.
-
The effect of food hardness during mastication on nociceptive transmission in the spinal cord was studied by analyzing complete Freund's adjuvant (CFA) induced nocifensive behavior and Fos expression. The behavioral study showed that the shortening of the withdrawal latency following CFA injection into the hind paw was depressed after a change in the given food hardness from soft to hard. The depression of nocifensive behavior in the rats with hard food was reversed after i.v. injection of naloxone. ⋯ Furthermore, the depression of Fos protein-LI cells following hard food intake was significantly inhibited after bilateral inferior alveolar nerve transection or bilateral ablation of the somatosensory cortex. These findings suggest that the change in food hardness during mastication might drive an opioid descending system through the trigeminal sensory pathway and somatosensory cortex resulting in an antinociceptive effect on chronic pain. However, IAN transection and cortical ablation did not induce 100% reversal of Fos expression, suggesting other than trigeminal sensory system may be involved in this phenomena, such as the pathway through the brainstem reticular formation.
-
Comparative Study
Methamphetamine-induced deficits of brain monoaminergic neuronal markers: distal axotomy or neuronal plasticity.
We examined the effects of methamphetamine (METH) on monoaminergic (i.e. dopamine and serotonin) axonal markers and glial cell activation in the rat brain. Our findings indicate that the loss of dopamine transporters (DAT), serotonin transporters (5-HTT), vesicular monoamine transporter type-2 (VMAT-2) and glial cell activation induced by METH in the striatum and in the central gray are consistent with a degenerative process. Our novel finding of METH effects on monoaminergic neurons in the central gray may have important implications on METH-induced hyperthermia. ⋯ In summary, our findings suggest two neurotoxic endpoints in the brain of METH-exposed animals. Brain regions exhibiting DAT and 5-HTT deficits that co-localize with decreased VMAT-2 levels and glial cell activation may represent monoaminergic terminal degeneration. However, the DAT and 5-HTT deficits in brain regions lacking a deficit in VMAT-2 and glial cell activation may reflect drug-induced modulation of these plasma membrane proteins.
-
A large body of evidence suggests that nitric oxide (NO) and ATP act as neurotransmitters in the regulatory mechanisms concerning several autonomic functions at the level of both the hypothalamus and the brain stem. In the present study, we investigated whether neuronal NO synthase containing neurones also express P2X(2) receptor subunit of the ATP-gated ion channel via double-labelling fluorescence immunohistochemistry. Our data demonstrate that a high percentage of neuronal NO synthase-immunoreactive neurones are also P2X(2)-immunoreactive in the rostral ventrolateral medulla (98%) and supraoptic nucleus of the hypothalamus (92%). ⋯ In contrast to the supraoptic nucleus, there was a lower percentage of co-localisation between NO synthase and P2X(2) receptor subunit in the paraventricular nucleus of the hypothalamus. In summary, this study demonstrates for the first time that there is a widespread co-localisation of neuronal NO synthase and P2X(2) receptor subunit in the hypothalamus and brain stem of the rat. Further studies are required to elucidate whether NO and ATP functionally interact within the hypothalamus and the brain stem.
-
Comparative Study
Region-specific changes in immediate early gene expression in response to sleep deprivation and recovery sleep in the mouse brain.
Previous studies have documented changes in expression of the immediate early gene (IEG) c-fos and Fos protein in the brain between sleep and wakefulness. Such expression differences implicate changes in transcriptional regulation across behavioral states and suggest that other transcription factors may also be affected. In the current study, we examined the expression of seven fos/jun family member mRNAs (c-fos, fosB, fos related antigen (fra)1, fra-2, junB, c-jun, and junD) and three other IEG mRNAs (egr-1, egr-3, and nur77) in mouse brain following short-term (6 h) sleep deprivation (SD) and 4 h recovery sleep (RS) after SD. ⋯ Among other IEGs, nur77 mRNA expression across conditions was similar to c-fos and fosB, egr-1 mRNA was elevated during SD in the cortex and basal forebrain, and egr-3 mRNA was elevated in the cortex during both SD and RS. The similarity of fosB and nur77 expression to c-fos expression indicates that these genes might also be useful markers of functional activity. Along with our previous results, the increased levels of fra-2 and egr-3 mRNAs during RS reported here suggest that increased mRNA expression during sleep is rare and may be anatomically restricted.