Habenula
Epithalamus
Neuroanatomical Tract-Tracing Techniques
Tegmentum Mesencephali
Electrolysis
Ibogaine
Lithium Carbonate
Azocines
Involvement of medullary tail-flick related neurons in descending facilitation evoked by chemical stimulation of rat lateral habenular nucleus. (1/111)
AIM: To study effects of sodium L-glutamate microinjection into lateral habenular nucleus (LHN) of rats on the firing of medullary tail-flick related neurons and tail-flick reflex (TF). METHODS: Using synchronous recording of unitary neuronal discharges and TF induced by noxious heat. RESULTS: Chemical stimulation of LHN induced an excitement of the on-cell spontaneous activity, an inhibition of the off-cell spontaneous activity with an enhancement of their TF related responses. The spontaneous firing rate of on-cells increased from 5.8 +/- 2.2 Hz to 10.9 +/- 3.4 Hz while the spontaneous firing rate of off-cells decreased from 11.8 +/- 2.2 Hz to 6.1 +/- 2.2 Hz. Meanwhile the TFL was shortened from 4.04 +/- 0.17 s to 2.97 +/- 0.13 s. CONCLUSION: The chemical stimulation of LHN produced a facilitating action on nociceptive spinal defensive reflex. This effect is brought out by the cooperation of on- and off-cells. (+info)Ca2+ permeability and kinetics of glutamate receptors in rat medial habenula neurones: implications for purinergic transmission in this nucleus. (2/111)
1. We have previously investigated P2X receptor-mediated synaptic currents in medial habenula neurones and shown that they can be calcium permeable. We now investigate the receptor properties of glutamate, the other, more abundant excitatory transmitter, to determine its receptor subtypes and their relative calcium permeability. This may have implications for the physiological role of the P2X receptors which mediate synaptic currents. 2. Using fast application of ATP, L-glutamate or kainate to nucleated patches, glutamate receptors were determined to be of the AMPA subtype but no functional P2X receptors were detected. 3. The deactivation and desensitization rates of the AMPA channel were determined to have time constants of 1.77 +/- 0.21 ms (n = 10) and 4.01 +/- 0.85 ms (n = 9) at -60 mV, respectively. AMPA receptors recovered from desensitization with two exponential components with time constants of 21.08 +/- 2.95 and 233.60 +/- 51.1 ms (n = 3). None of the deactivation or desensitization properties of the GluR channels depended on membrane potential. 4. The current-voltage relationship under different ionic conditions revealed that the GluR channel was equally permeable to Cs+ and Na+ but relatively impermeable to Ca2+ (PCa/PCs = 0.13, n = 6). 5. For both synaptic currents and somatic currents activated by fast application of L-glutamate to nucleated patches, decay time constants were similar at +/-60 mV in the presence of Mg2+ ions. Thus GluR channels appear to be of the AMPA subtype and not the NMDA subtype. 6. Thus, under the conditions of this study, neurones of the medial habenula lack functional NMDA receptors and possess AMPA receptors that have low permeability to Ca2+. We conclude that the P2X receptor-mediated synaptic currents are the only calcium-permeable fast-transmitter gated currents in these neurones which may be important for their physiological function. (+info)Neuropilin-2 is required in vivo for selective axon guidance responses to secreted semaphorins. (3/111)
Neuropilins are receptors for class 3 secreted semaphorins, most of which can function as potent repulsive axon guidance cues. We have generated mice with a targeted deletion in the neuropilin-2 (Npn-2) locus. Many Npn-2 mutant mice are viable into adulthood, allowing us to assess the role of Npn-2 in axon guidance events throughout neural development. Npn-2 is required for the organization and fasciculation of several cranial nerves and spinal nerves. In addition, several major fiber tracts in the brains of adult mutant mice are either severely disorganized or missing. Our results show that Npn-2 is a selective receptor for class 3 semaphorins in vivo and that Npn-1 and Npn-2 are required for development of an overlapping but distinct set of CNS and PNS projections. (+info)Neuropilin-2 regulates the development of selective cranial and sensory nerves and hippocampal mossy fiber projections. (4/111)
Neuropilin-1 and neuropilin-2 bind differentially to different class 3 semaphorins and are thought to provide the ligand-binding moieties in receptor complexes mediating repulsive responses to these semaphorins. Here, we have studied the function of neuropilin-2 through analysis of a neuropilin-2 mutant mouse, which is viable and fertile. Repulsive responses of sympathetic and hippocampal neurons to Sema3F but not to Sema3A are abolished in the mutant. Marked defects are observed in the development of several cranial nerves, in the initial central projections of spinal sensory axons, and in the anterior commissure, habenulo-interpeduncular tract, and the projections of hippocampal mossyfiber axons in the infrapyramidal bundle. Our results show that neuropilin-2 is an essential component of the Sema3F receptor and identify key roles for neuropilin-2 in axon guidance in the PNS and CNS. (+info)Neuroprotective role of dopamine against hippocampal cell death. (5/111)
Glutamate excitotoxicity plays a key role in the induction of neuronal cell death occurring in many neuropathologies, including epilepsy. Systemic administration of the glutamatergic agonist kainic acid (KA) is a well characterized model to study epilepsy-induced brain damage. KA-evoked seizures in mice result in hippocampal cell death, with the exception of some strains that are resistant to KA excitotoxicity. Little is known about the factors that prevent epilepsy-related neurodegeneration. Here we show that dopamine has such a function through the activation of the D2 receptor (D2R). D2R gene inactivation confers susceptibility to KA excitotoxicity in two mouse strains known to be resistant to KA-induced neurodegeneration. D2R-/- mice develop seizures when administered KA doses that are not epileptogenic for wild-type (WT) littermates. The spatiotemporal pattern of c-fos and c-jun mRNA induction well correlates with the occurrence of seizures in D2R-/- mice. Moreover, KA-induced seizures result in extensive hippocampal cell death in D2R-/- but not WT mice. In KA-treated D2R-/- mice, hippocampal neurons die by apoptosis, as indicated by the presence of fragmented DNA and the induction of the proapoptotic protein BAX. These results reveal a central role of D2Rs in the inhibitory control of glutamate neurotransmission and excitotoxicity. (+info)Regulation of the sensitivity of acetylcholine receptors to nicotine in rat habenula neurons. (6/111)
Time-dependent changes in nicotinic acetylcholine receptor (nAChR) function were studied in acutely isolated medial habenula neurons during whole-cell perfusion. The peak amplitude of inward currents induced by 1 s pulses of nicotinic agonists, applied at 30 s intervals, gradually increased over the first several minutes of whole-cell recording. The ratio of response amplitudes at 1 and 15 min (t15/t1) was 1.9. Run-up of responses occurred independently of channel activation and was specific to nAChRs. The channel blocker chlorisondamine (30 microM), co-applied with nicotine, was used to irreversibly block the majority (91 %) of the nAChRs that opened in the first 2 min of recording. Run-up in the remaining 9 % unblocked channels assessed at 15 min (t15/t2 = 3.4) was similar to that in control cells not exposed to nicotine and chlorisondamine simultaneously, implying that run-up is not due to the incorporation of new receptors. A marked alteration in the sensitivity of nAChRs to extracellular Ca2+ was also observed during whole-cell perfusion. The ratio of current amplitudes obtained in 0.2 and 4.0 mM Ca2+ changed from 0.54 (t = 5 min) to 0.82 (t = 30 min). Inward rectification of nicotine-induced responses was reduced during internal dialysis. Voltages for half-maximal conductance were -23.0 and -13.8 mV at 2 and 15 min, respectively. Inclusion of either free Mg2+ ( approximately 2 mM) or spermine (100 microM) in the internal solution counteracted the change in rectification, but did not prevent run-up. The period of run-up was followed by a use-dependent run-down phase. Little run-down in peak current amplitude was induced provided that agonist was applied infrequently (5 min intervals), whereas applications at 30 s intervals produced a loss of channel function after approximately 15 min whole-cell perfusion. The time at which run-down began ( approximately 5-30 min) was correlated with the initial rate of nAChR desensitization ( approximately 200-4000 ms); slowly desensitizing nicotinic currents demonstrated delayed run-down. We suggest that run-up of nAChR-mediated responses does not require receptor activation and may result from a change in channel open probability. We also hypothesize that channel run-down reflects accumulation of nAChRs in long-lived desensitized/inactivated states. (+info)A nodal signaling pathway regulates the laterality of neuroanatomical asymmetries in the zebrafish forebrain. (7/111)
Animals show behavioral asymmetries that are mediated by differences between the left and right sides of the brain. We report that the laterality of asymmetric development of the diencephalic habenular nuclei and the photoreceptive pineal complex is regulated by the Nodal signaling pathway and by midline tissue. Analysis of zebrafish embryos with compromised Nodal signaling reveals an early role for this pathway in the repression of asymmetrically expressed genes in the diencephalon. Later signaling mediated by the EGF-CFC protein One-eyed pinhead and the forkhead transcription factor Schmalspur is required to overcome this repression. When expression of Nodal pathway genes is either absent or symmetrical, neuroanatomical asymmetries are still established but are randomized. This indicates that Nodal signaling is not required for asymmetric development per se but is essential to determine the laterality of the asymmetry. (+info)Inhibitory effects of barbiturates on nicotinic acetylcholine receptors in rat central nervous system neurons. (8/111)
BACKGROUND: Neuronal nicotinic acetylcholine receptors (nAChRs) are widely expressed in the central and autonomic nervous systems. The authors have previously shown that depressant and convulsant barbiturates both inhibit the ganglion-type nAchRs in PC12 cells. However, the central and gangliontype receptors have different subunit composition and pharmacologic properties. In this study, the authors investigated the effects of thiopental, depressant [R(-)] and convulsant [S(+)] stereoisomers of 1-methyl-5 phenyl-5-propyl barbituric acid (MPPB) on neuronal nAChRs in the rat central nervous system to explore significance of these effects in barbiturate anesthesia. METHODS: Whole-cell currents were measured in acutely dissociated rat medial habenula (MHb) neurons by applying 10 or 100 microM nicotine in the absence or presence of thiopental 3-100 microM. Effects of R(-)- and S(+)-MPPB on the nicotine-induced current were also studied. RESULTS: Thiopental suppressed the nicotine-elicited inward current and accelerated the current decay dose-dependently at the clinical relevant concentrations. R(-)- and S(+)-MPPB both inhibited the nicotine-induced current dose-dependently without augmenting the current decay. There was no significant difference in the magnitudes of inhibition by R(-)- and S(+)-MPPB. CONCLUSIONS: Although thiopental suppressed the current mediated through native nAchRs in rat MHb neurons at the clinically relevant concentrations, the depressant and convulsant stereoisomers of MPPB both inhibited the current in the same extent. These findings are consistent with the results previously obtained in the ganglion-type receptors of PC12 cells and suggest that inhibition of nAChRs in MHb neurons is not directly relevant to the hypnotic or anticonvulsive actions of barbiturates. (+info)The habenula is a small, paired nucleus located in the epithalamus region of the brain. It plays a crucial role in the modulation of various functions such as mood, reward, and motivation. The habenula can be further divided into two subregions: the medial and lateral habenula.
The medial habenula is involved in the regulation of emotional behaviors, including responses to stress and anxiety. It receives inputs from several brain regions associated with emotion, such as the amygdala and hippocampus, and projects to the interpeduncular nucleus (IPN) in the midbrain.
The lateral habenula is primarily involved in processing aversive stimuli and modulating dopaminergic reward pathways. It receives inputs from various regions associated with motivation, learning, and memory, such as the prefrontal cortex, basal ganglia, and thalamus. The lateral habenula then projects to the midbrain's dopamine-producing neurons in the ventral tegmental area (VTA) and substantia nigra pars compacta (SNc), which are critical components of the brain's reward system.
Dysfunction of the habenula has been implicated in several neurological and psychiatric disorders, including depression, anxiety, addiction, and schizophrenia.
The epithalamus is a part of the brain that is located in the diencephalon, near the thalamus. It includes several small structures, such as the habenula and the pineal gland. The epithalamus plays a role in regulating sleep-wake cycles, hormone production, and emotional responses. It also has connections to other parts of the brain that are involved in vision, hearing, and movement.
The main function of the epithalamus is to regulate the release of hormones from the pituitary gland, which is located at the base of the brain. The epithalamus contains specialized cells called neurosecretory cells, which produce and release hormones that control various bodily functions, such as growth, development, and reproduction.
The epithalamus also plays a role in regulating mood and emotional responses. It has connections to the limbic system, which is a network of structures involved in emotion, behavior, and long-term memory. The habenula, which is part of the epithalamus, is thought to be involved in processing rewarding and aversive stimuli, and may play a role in addiction and depression.
In addition, the pineal gland, which is also part of the epithalamus, produces melatonin, a hormone that helps regulate sleep-wake cycles. The production of melatonin is influenced by light exposure, with higher levels produced at night and lower levels during the day.
Overall, the epithalamus is an important part of the brain that plays a role in various physiological and psychological processes. Dysfunction of the epithalamus has been implicated in several neurological and psychiatric disorders, such as Parkinson's disease, depression, and addiction.
Neuroanatomical tract-tracing techniques are a set of neuroanatomical methods used to map the connections and pathways between different neurons, neural nuclei, or brain regions. These techniques involve introducing a tracer substance into a specific population of neurons, which is then transported through the axons and dendrites to other connected cells. The distribution of the tracer can be visualized and analyzed to determine the pattern of connectivity between different brain areas.
There are two main types of neuroanatomical tract-tracing techniques: anterograde and retrograde. Anterograde tracing involves introducing a tracer into the cell body or dendrites of a neuron, which is then transported to the axon terminals in target areas. Retrograde tracing, on the other hand, involves introducing a tracer into the axon terminals of a neuron, which is then transported back to the cell body and dendrites.
Examples of neuroanatomical tract-tracing techniques include the use of horseradish peroxidase (HRP), fluorescent tracers, radioactive tracers, and viral vectors. These techniques have been instrumental in advancing our understanding of brain circuitry and function, and continue to be an important tool in neuroscience research.
The tegmentum mesencephali, also known as the mesencephalic tegmentum, is a region in the midbrain (mesencephalon) of the brainstem. It contains several important structures including the periaqueductal gray matter, the nucleus raphe, the reticular formation, and various cranial nerve nuclei. The tegmentum mesencephali plays a crucial role in various functions such as pain modulation, sleep-wake regulation, eye movement control, and cardiovascular regulation.
Electrolysis is a medical procedure that involves the use of electrical current to permanently remove hair growth. It works by passing a thin, solid metal electrode (called a probe) into the natural opening of the hair follicle and applying an electrical charge to destroy the hair root. This process can be used to remove hair from any part of the body, including the face, legs, arms, underarms, and bikini area.
During electrolysis, a trained professional called an electrologist inserts a small needle into the hair follicle and applies a mild electrical current. The current heats up and destroys the hair root, preventing future growth. Multiple treatments are usually necessary to achieve permanent hair removal, as only one or two hairs can be treated at a time.
Electrolysis is considered a safe and effective method for permanent hair removal, but it can cause some discomfort during and after treatment. Common side effects include redness, swelling, and tenderness in the treated area. These side effects typically resolve within a few hours to a few days after treatment.
It's important to note that electrolysis should only be performed by a licensed and trained electrologist. Improper technique can cause scarring, infection, or other complications. Before undergoing electrolysis, it's recommended to consult with a dermatologist or other healthcare provider to discuss the risks and benefits of the procedure.
Ibogaine is a naturally occurring psychoactive alkaloid found in the root bark of the African shrub, Tabernanthe iboga. It has been used traditionally in West African spiritual practices and healing rituals for centuries. In the medical field, ibogaine has been explored as an experimental treatment for substance abuse disorders, particularly for opioid addiction, due to its ability to reduce withdrawal symptoms and cravings. However, its use is not widely accepted or approved by regulatory agencies due to safety concerns, including potential cardiac toxicity and psychological adverse effects. Therefore, it's essential to conduct thorough research and consult with medical professionals before considering ibogaine treatment.
Lithium carbonate is a medical inorganic salt that is commonly used as a medication, particularly in the treatment of bipolar disorder. It works by stabilizing mood and reducing the severity and frequency of manic episodes. Lithium carbonate is available in immediate-release and extended-release forms, and it is typically taken orally in the form of tablets or capsules.
The medical definition of lithium carbonate is: "A white, crystalline powder used as a mood-stabilizing drug, primarily in the treatment of bipolar disorder. It acts by reducing the availability of sodium and potassium ions within nerve cells, which alters the electrical activity of the brain and helps to regulate mood. Lithium carbonate is also used in the treatment of cluster headaches and to reduce aggression in patients with behavioral disorders."
It's important to note that lithium carbonate requires careful medical supervision due to its narrow therapeutic index, meaning there is a small range between an effective dose and a toxic one. Regular monitoring of blood levels is necessary to ensure safe and effective treatment.
Azocines are a class of organic compounds that contain a seven-membered ring with two nitrogen atoms adjacent to each other, connected by a single bond. This results in an unusual structure where the two nitrogen atoms share a double bond, creating a unique azoxy functional group. The name "azocine" is derived from the fact that it contains both azo (-N=N-) and cyclic structures.
Azocines are not commonly found in nature, but they can be synthesized in the laboratory for use in various applications, such as pharmaceuticals or materials science. However, due to their unique structure and reactivity, they may pose challenges during synthesis and handling.
It's worth noting that azocines do not have a specific medical definition, as they are not a type of drug or treatment. Instead, they are a class of chemical compounds with potential applications in various fields, including medicine.
Neural pathways, also known as nerve tracts or fasciculi, refer to the highly organized and specialized routes through which nerve impulses travel within the nervous system. These pathways are formed by groups of neurons (nerve cells) that are connected in a series, creating a continuous communication network for electrical signals to transmit information between different regions of the brain, spinal cord, and peripheral nerves.
Neural pathways can be classified into two main types: sensory (afferent) and motor (efferent). Sensory neural pathways carry sensory information from various receptors in the body (such as those for touch, temperature, pain, and vision) to the brain for processing. Motor neural pathways, on the other hand, transmit signals from the brain to the muscles and glands, controlling movements and other effector functions.
The formation of these neural pathways is crucial for normal nervous system function, as it enables efficient communication between different parts of the body and allows for complex behaviors, cognitive processes, and adaptive responses to internal and external stimuli.