The present study was aimed to explore the effects of intraperitoneal injection of growth hormone releasing peptide-6 (GHRP-6), a ghrelin receptor agonist, on food intake and neuronal activity of feeding-related nuclei in the hypothalamus of NMRI mice. Accumulated amount of food intake was measured, and total number of c-fos immunoreactive neurons in arcuate nucleus (ARC), paraventricular nucleus (PVN) and supraoptic nucleus (SON) was counted by immunohistochemistry at 1, 3 and 6 h after the GHRP-6 injection. The results showed that GHRP-6 significantly increased the amount of food intake with a peak at 3 h after the GHRP-6 injection. Meanwhile, GHRP-6 could promote c-fos expression in the ARC and PVN independent of food intake, and the total number of c-fos immunoreactive neurons was peaked at 1 h after injection and then decreased gradually. These results suggest that GHRP-6 may increase food intake in time-dependent manner, which is associated with up-regulations of c-fos protein expression in the ARC and PVN.
Animals ; Arcuate Nucleus of Hypothalamus ; Eating ; Immunohistochemistry ; Male ; Mice ; Neurons ; Oligopeptides ; Paraventricular Hypothalamic Nucleus ; Proto-Oncogene Proteins c-fos ; Receptors, Ghrelin ; Supraoptic Nucleus

In addition to classical synaptic transmission, information is transmitted between cells via the activation of extrasynaptic receptors that generate persistent tonic current in the brain. While growing evidence supports the presence of tonic NMDA current (INMDA) generated by extrasynaptic NMDA receptors (eNMDARs), the functional significance of tonic I(NMDA) in various brain regions remains poorly understood. Here, we demonstrate that activation of eNMDARs that generate I(NMDA) facilitates the α-amino-3-hydroxy-5-methylisoxazole-4-proprionate receptor (AMPAR)-mediated steady-state current in supraoptic nucleus (SON) magnocellular neurosecretory cells (MNCs). In low-Mg2+ artificial cerebrospinal fluid (aCSF), glutamate induced an inward shift in I(holding) (I(GLU)) at a holding potential (V(holding)) of -70 mV which was partly blocked by an AMPAR antagonist, NBQX. NBQX-sensitive I(GLU) was observed even in normal aCSF at V(holding) of -40 mV or -20 mV. I(GLU) was completely abolished by pretreatment with an NMDAR blocker, AP5, under all tested conditions. AMPA induced a reproducible inward shift in I(holding) (I(AMPA)) in SON MNCs. Pretreatment with AP5 attenuated I(AMPA) amplitudes to ~60% of the control levels in low-Mg2+ aCSF, but not in normal aCSF at V(holding) of -70 mV. I(AMPA) attenuation by AP5 was also prominent in normal aCSF at depolarized holding potentials. Memantine, an eNMDAR blocker, mimicked the AP5-induced I(AMPA) attenuation in SON MNCs. Finally, chronic dehydration did not affect I(AMPA) attenuation by AP5 in the neurons. These results suggest that tonic I(NMDA), mediated by eNMDAR, facilitates AMPAR function, changing the postsynaptic response to its agonists in normal and osmotically challenged SON MNCs.
alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid* ; Brain ; Cerebrospinal Fluid ; Dehydration ; Glutamic Acid ; Memantine ; N-Methylaspartate* ; Neurons ; Receptors, AMPA ; Receptors, N-Methyl-D-Aspartate* ; Supraoptic Nucleus ; Synaptic Transmission

The present study was designed to investigate the inhibitory effects of intravenous general anesthetic propofol (0.1-3.0 mmol/L) on excitatory synaptic transmission in supraoptic nucleus (SON) neurons of rats, and to explore the underlying mechanisms by using intracellular recording technique and hypothalamic slice preparation. It was observed that stimulation of the dorsolateral region of SON could elicit the postsynaptic potentials (PSPs) in SON neurons. Of the 8 tested SON neurons, the PSPs of 7 (88%, 7/8) neurons were decreased by propofol in a concentration-dependent manner, in terms of the PSPs' amplitude (P < 0.01), area under curve, duration, half-width and 10%-90% decay time (P < 0.05). The PSPs were completely and reversibly abolished by 1.0 mmol/L propofol at 2 out of 7 tested cells. The depolarization responses induced by pressure ejection of exogenous glutamate were reversibly and concentration-dependently decreased by bath application of propofol. The PSPs and glutamate-induced responses recorded simultaneously were reversibly and concentration-dependently decreased by propofol, but 0.3 mmol/L propofol only abolished PSPs. The excitatory postsynaptic potentials (EPSPs) of 7 cells increased in the condition of picrotoxin (30 µmol/L, a GABA(A) receptor antagonist) pretreatment. On this basis, the inhibitory effects of propofol on EPSPs were decreased. These data indicate that the presynaptic and postsynaptic mechanisms may be both involved in the inhibitory effects of propofol on excitatory synaptic transmission in SON neurons. The inhibitory effects of propofol on excitatory synaptic transmission of SON neurons may be related to the activation of GABA(A) receptors, but at a high concentration, propofol may also act directly on glutamate receptors.
Anesthetics, Intravenous ; pharmacology ; Animals ; Excitatory Postsynaptic Potentials ; drug effects ; GABA-A Receptor Antagonists ; pharmacology ; Glutamic Acid ; pharmacology ; In Vitro Techniques ; Neurons ; drug effects ; Propofol ; pharmacology ; Rats ; Receptors, Glutamate ; metabolism ; Supraoptic Nucleus ; cytology

The purpose of this study is to investigate the antinociceptive effects of ginsenosides on toothache. c-Fos immunoreactive (IR) neurons were examined after noxious intrapulpal stimulation (NS) by intrapulpal injection of 2 M KCl into upper and lower incisor pulps exposed by bone cutter in Sprague Dawley rats. The number of Fos-IR neurons was increased in the trigeminal subnucleus caudalis (Vc) and the transitional region between Vc and subnucleus interpolaris (Vi) by NS to tooth. The intradental NS raised arterial blood pressure (BP) and heart rate (HR). The number of Fos-IR neurons was also enhanced in thalamic ventral posteromedial nucleus (VPMN) and centrolateral nucleus (CLN) by NS to tooth. The intradental NS increased the number of Fos-IR neurons in the nucleus tractus solitarius (NTS) and rostral ventrolateral medulla (RVLM), hypothalamic supraoptic nucleus (SON) and paraventricular nucleus (PVN), central cardiovascular regulation centers. Ginsenosides reduced the number of c-Fos-IR increased by NS to tooth in the trigeminal Vc and thalamic VPMN and CLN. Naloxone, an opioid antagonist, did not block the effect of ginsenoside on the number of Fos-IR neurons enhanced by NS to tooth in the trigeminal Vc and thalamic VPMN and CLN. Ginsenosides ameliorated arterial BP and HR raised by NS to tooth and reduced the number of Fos-IR neurons increased by NS to tooth in the NTS, RVLM, hypothalamic SON, and PVN. These results suggest that ginsenosides have an antinociceptive effect on toothache through non-opioid system and attenuates BP and HR increased by NS to tooth.
Animals ; Arterial Pressure ; Brain ; Ginsenosides ; Heart Rate ; Incisor ; Naloxone ; Neurons ; Paraventricular Hypothalamic Nucleus ; Rats ; Rats, Sprague-Dawley ; Solitary Nucleus ; Supraoptic Nucleus ; Tooth ; Toothache ; Ventral Thalamic Nuclei

Arginine vasopressin (AVP) is a neuropeptide with vasoconstrictive, antidiuretic, cardiovascular regulative and hepatic glycogenolysis effects, that also affects other behaviors including modulating learning. A number of studies on AVP regulation have been conducted in various metabolic diseases (disorders). In this study, the immunoreactivities of AVP in the paraventricular nucleus (PVN) and supraoptic nucleus (SON) and mRNA expressions in the hypothalamus were investigated by immunohistochemistry and quantitative real-time PCR (RT-qPCR) in stroke-prone spontaneously hypertensive rats at different ages (i.e., at postnatal months [PM] 1, 8, and 12). Blood glucose levels in the PM 8 group were higher than in the other groups. However, cresyl violet positive neurons were detected in the PVN and SON of all animals, and numbers of cresyl violet positive neurons were similar in all aged groups. In addition, AVP immunoreactivity was detected in the PVN and SON of all age groups, and AVP immunoreactivity and mRNA expression levels were found to be increased in proportion to age by immunohistochemistry and RT-qPCR. These results suggest that the diabetic condition is temporally generated after hypertension has developed. Furthermore, our findings suggest that increased AVP expressions in the hypothalamic PVN and SON are associated with hypertension by age.
Aged ; Animals ; Arginine ; Arginine Vasopressin ; Benzoxazines ; Blood Glucose ; Glycogenolysis ; Humans ; Hypertension ; Hypothalamus ; Immunohistochemistry ; Learning ; Metabolic Diseases ; Molybdenum ; Neurons ; Neuropeptides ; Oxides ; Paraventricular Hypothalamic Nucleus ; Rats, Inbred SHR ; Real-Time Polymerase Chain Reaction ; RNA, Messenger ; Supraoptic Nucleus ; Viola

To investigate the effects of novel intravenous general anesthetic propofol on membrane electrophysiological characteristics and action potential (AP) of the supraoptic nucleus (SON) neurons and possible ionic mechanisms, intracellular recordings were conducted in SON neurons from the coronal hypothalamic slice preparation of adult male Sprague Dawley (SD) rats. The results showed that bath application of 0.1 mmol/L propofol induced a significant decline in resting potential (P < 0.01), and higher concentrations of propofol (0.3 and 1.0 mmol/L) decreased time constant and slope resistance of cell membrane (P < 0.01). Under the hyperpolarizing current pulses exceeding 0.5 nA, an anomalous rectification was induced by hyperpolarization-activated cation channel (I(h) channel) in 11 out of 18 tested SON neurons. Bath of propofol reversibly decreased the anomalous rectification. Moreover, 0.1 mmol/L propofol elevated threshold level (P < 0.01) and decreased Max L. slope (P < 0.05) of the spike potential in SON neurons. Interestingly, 0.3 and 1.0 mmol/L propofol nullified APs in 6% (1/18) and 71% (12/17) tested SON neurons, respectively. In the SON neurons where APs were not nullified, propofol (0.3 mmol/L) decreased the amplitude of spike potential (P < 0.05). The higher concentrations of propofol (0.3 and 1.0 mmol/L) decreased firing frequencies evoked by depolarizing current pulses (0.1-0.7 nA), and shifted the current intensity-firing frequency relation curves downward and to the right. These results suggest that propofol decreases the excitability of SON neurons by inhibiting I(h) and sodium channels.
Action Potentials ; drug effects ; Anesthetics, Intravenous ; pharmacology ; Animals ; Cyclic Nucleotide-Gated Cation Channels ; antagonists & inhibitors ; Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels ; Hypothalamus ; drug effects ; physiology ; In Vitro Techniques ; Male ; Potassium Channels ; Propofol ; pharmacology ; Rats ; Rats, Sprague-Dawley ; Sodium Channel Blockers ; pharmacology ; Supraoptic Nucleus ; drug effects ; physiology

BDNF belongs to the neurotrophin family and important molecular mediator of functional and structural plasticity. The highest levels of BDNF are found in the hippocampus and hypothalamus of the adult rat. Hypothalamus is important because of its high degree of plasticity, but little is known about distribution of BDNF in hypothalamic nuclei. Therefore, it is necessary to study distribution and expression pattern of BDNF in each hypothalamic nuclei to understand changes of BDNF through various neural damages including spinal cord injury. Through this experiment, we found specific BDNF expression pattern in some regions of hypothalamus and the results are as follows. 1) BDNF expressions were found in median eminence, arcuate nucleus, supraoptic nucleus, and periventricular nucleus of rat hypothalamus. 2) BDNF immunoreactive cells and nerve fibers were of various shapes and sizes. 3) Glial cells also express BDNF in certain hypothalamic nuclei. These results seem to be useful for future investigations of neurochemical changes in the hypothalamus induced by various neural trauma or degenerative changes
Adult ; Animals ; Arcuate Nucleus ; Brain-Derived Neurotrophic Factor ; Hippocampus ; Humans ; Hypothalamus ; Median Eminence ; Nerve Fibers ; Neuroglia ; Plastics ; Rats ; Spinal Cord Injuries ; Supraoptic Nucleus

In the present study, we performed immunohistochemical studies to investigate the detailed distribution of insulin-like growth factor binding protein 7 (IGFBP7) in the central nervous system of adult rats. Twelve adult (4~6 month old) Sprague-Dawley rats were examined in this study. Immunohistochemistry using specific antibodies against IGFBP7 was performed in accordance with the free-floating method. In the present study, IGFBP7 immunoreactivity was observed in the cerebral cortex, hippocampus, brainstem, cerebellum and spinal cord. In the cerebral cortex, heavily stained neurons were seen in layers II-VI. In the hippocampus, pyramidal cells in CA1-3 region were strongly immunoreactive for IGFBP7. Strong immunoreactive neurons were also found in the supraoptic nucleus, paraventricular nucleus, periaqueductal gray and oculomotor nucleus. In the cerebellum, IGFBP7 immunoreactivity was prominent in the Purkinje cells and cerebellar output neurons. IGFBP7-immunoreactive neurons were prominent in the superior vestibular nucleus, cochlear nucleus, trigeminal motor nucleus, nucleus of the trapezoid, and facial nucleus. IGFBP7-immunoreactive neurons were also observed mainly in the anterior horn of the spinal cord. The first demonstration of IGFBP7 localization in the whole brain may provide useful data for the future investigations on the structural and functional properties of IGFBP7.
Adult ; Animals ; Antibodies ; Brain ; Brain Stem ; Carrier Proteins ; Central Nervous System ; Cerebellum ; Cerebral Cortex ; Cochlear Nucleus ; Hippocampus ; Horns ; Humans ; Immunohistochemistry ; Neurons ; Paraventricular Hypothalamic Nucleus ; Periaqueductal Gray ; Purkinje Cells ; Pyramidal Cells ; Rats ; Rats, Sprague-Dawley ; Spinal Cord ; Supraoptic Nucleus ; Trigeminal Nuclei

OBJECTIVETo study the changes in the plasticity of the neurons and astrocytes in the paraventricular nucleus (PVN) and supraoptic nucleus (SON) of the hypothalamus of rats exposed to a humid and hot environment.

METHODSThe rats were subjected to stimulation with a humid and hot environment for 120 min in a climate chamber (dry bulb temperature of 40.0-/+0.5 degrees C with relative humidity of 60-/+5%). During the exposure, the behavioral responses of the rats were observed, and the changes in the expressions of Fos and GFAP in the PVN and SON in response to the exposure evaluated using immunohistochemical ABC methods.

RESULTSExposure to a humid and hot environment caused restlessness and agitation in the rats, which showed increased respiratory frequency and scratching of the face with the forelimbs. Two rats died after the 120-min exposure. Significantly increased expressions of Fos and GFAP were detected in the PVN and SON following the exposure as compared with the control group.

CONCLUSIONThe neurons and astrocytes in the PVN and SON both participate in the regulation of responses to exposure to a humid and hot environment.

Animals ; Astrocytes ; cytology ; physiology ; Glial Fibrillary Acidic Protein ; analysis ; Hot Temperature ; Humidity ; Hypothalamus ; cytology ; metabolism ; Immunohistochemistry ; Male ; Neuronal Plasticity ; physiology ; Neurons ; cytology ; physiology ; Oncogene Proteins v-fos ; analysis ; Paraventricular Hypothalamic Nucleus ; cytology ; metabolism ; Random Allocation ; Rats ; Rats, Sprague-Dawley ; Supraoptic Nucleus ; cytology ; metabolism

The role of neuropeptides in the central nervous system (CNS) has received increasing attention. Numerous peptide molecules are found in the mammalian CNS and many of them are thought to act as either neurotransmitters or neuromodulators. The neuropeptides found in high concentration in the hypothalamus include vasopressin (VP), vasoactive intestinal polypeptide, somatostatin, and oxytocin. The main approches to assess the involvement of neuropeptides can be focused on functions affecting the aging of the brain. Morphological aging of the CNS has been characterized by degenerative changes of fiber connections and cell loss, although degeneration does not always occur to the same extent throughout various parts of the brain and, moreover, varies for different cell types. Despite of many studies in VP containing neurons , there exist discrepancies in results about the changes of aged rat brain. The aim of the present study is, therefore, to investigative possible changes in the number and morphology of VPimmunoreactive neurons with aging in each area of the hypothalmus of the aged rats. As a result, the number of VP-immunoreactive neurons was decreased in hypothalamus nucleus of aged group. Especially, in VP-immunoreactive neurons of hypothalamus, the size of neuronal cell body and nuclei in aged group is larger than in young group and the fiber density of immunoreactivity neurons of median eminance (ME) in aged group is stronger than in young group. But, the total number of VP-immunoreactive neurons in the suprachiasmatic nucleus (SCN) of the aged group is larger than in the young group. These studies indicate the involvement of VP-immunoreactive neurons in aging process of hypothalamus, and aging process may affect the synthesis of VP in the neurons of hypothalamic nuclei. Whereas, in VP expression, aging process induces an enlargement of the cell size of surviving neurons to compensate.
Aging ; Animals ; Brain ; Cell Size ; Central Nervous System ; Hypothalamus* ; Neurons* ; Neuropeptides ; Neurotransmitter Agents ; Oxytocin ; Paraventricular Hypothalamic Nucleus ; Rats* ; Somatostatin ; Suprachiasmatic Nucleus ; Supraoptic Nucleus ; Vasoactive Intestinal Peptide ; Vasopressins