dizocilpine-maleate and saclofen

Levetiracetam (LEV) is a broad-spectrum antiepileptic drug with neuroprotective properties and novel mechanisms of action. Some evidence suggests that LEV may impact adult neurogenesis, but the results are controversial. The present study was aimed to evaluate the effects of LEV on the proliferation and differentiation of rat embryonic neural stem cells (NSCs) and to explore the role of GABA. NSCs were isolated from rat fetal ganglionic eminence at embryonic day 14.5. The effects of LEV on viability, proliferation, neurosphere formation, and neuronal or astroglial differentiation of NSCs were assessed using resazurin, BrdU incorporation, immunocytochemistry, quantitative real-time PCR, and western blotting. Additionally, we addressed the relationship between treatment with NMDA and GABA. The data showed that LEV (50 μM) significantly increased the number (p < 0.01) and diameter of neurospheres (p < 0.05), enhanced proliferation (p < 0.01), and promoted neuronal differentiation, as revealed by significantly increased expressions of DCX and NeuN. The expressions of astroglial markers, GFAP and Olig2, were markedly reduced. The addition of MK801 (10 μM) significantly diminished neurospheres growth (p < 0.001), decreased the number of proliferating cells (p < 0.01), and reduced the number of new neurons (p < 0.001) but increased the astroglial cells (p < 0.001) induced by LEV. Co-treatment with saclofen (25 μM) did not significantly affect LEV-induced NSCs proliferation and differentiation.. Our findings suggest that LEV may enhance rat embryonic neurogenesis mainly through an NMDA receptor-mediated mechanism.

Topics: Animals; Baclofen; Biomarkers; Cell Differentiation; Cell Proliferation; Cell Survival; Dizocilpine Maleate; Doublecortin Protein; Embryo, Mammalian; Female; Levetiracetam; Male; Nerve Tissue Proteins; Neural Stem Cells; Neurogenesis; Neurons; Rats, Wistar; Receptors, N-Methyl-D-Aspartate; RNA, Messenger; Spheroids, Cellular

The second-order relay neurons of the slowly-adapting pulmonary stretch receptors (SARs) are called pump neurons (P cells) and are located in the nucleus tractus solitarii (NTS). We have shown recently that P cells do not act merely as simple relay neurons of SAR afferents but also receive rhythmic inputs from the central respiratory system. This study aimed to analyze two aspects of the respiratory inputs to P cells: (1) suppression of P cell firing at early inspiration (eI suppression) and (2) facilitation of P cell firing at around the period from late inspiration to early expiration (IE facilitation). This study employed extracellular recordings combined with iontophoretic applications of neuroactive drugs to single P cells, in Nembutal-anesthetized, paralyzed, and artificially ventilated rats. The results showed that several excitatory and inhibitory neurotransmitters were involved in these synaptic events. First, the glycine antagonist strychnine and the GABA(A) antagonist bicuculline were applied to identify the neurotransmitters acting in eI suppression. Strychnine greatly diminished eI suppression, but bicuculline had little effect. This suggested that eI suppression was elicited by inspiratory neurons that were glycinergic and had a decrementing firing pattern. Second, on the other hand bicuculline markedly enhanced IE facilitation as well as the baseline frequency of P cell firing. The enhancement of IE facilitation was distinctive even when the effects of increased baseline firing on this enhancement were taken into account. Third, IE facilitation was diminished by applications of the NMDA glutamate receptor antagonists D-2-amino-5-phosphonovaleric acid (APV) and dizocilpine (MK-801). These results suggested that glutamatergic synapses on P cells from some unidentified respiratory neurons form excitatory inputs for IE facilitation and GABA(A) receptor-mediated processes control the strength of IE facilitation, possibly at the presynaptic level. Finally, iontophoretic application of the non-NMDA glutamate receptor antagonist, 6-cyano-7-nitroquinoxaline-2, 3-dione disodium (CNQX), almost completely abolished P cell firing in response to both lung inflation and electrical stimulation of the vagus nerve. This confirmed the previous report that glutamate is the primary neurotransmitter at the synapses between SAR afferents and P cells. We concluded that complicated synaptic inputs involving glycinergic and GABAergic inhibitions, and non-NMDA and NM

Topics: 2-Amino-5-phosphonovalerate; 6-Cyano-7-nitroquinoxaline-2,3-dione; Action Potentials; Animals; Baclofen; Bicuculline; Dizocilpine Maleate; Excitatory Amino Acid Antagonists; GABA Antagonists; gamma-Aminobutyric Acid; Glycine; Glycine Agents; Neural Inhibition; Neurons; Rats; Rats, Wistar; Reaction Time; Receptors, N-Methyl-D-Aspartate; Solitary Nucleus; Strychnine; Synapses

To elucidate the role of GABAB receptors in the regulation of the electrical activity of magnocellular neurons of the supraoptic nucleus (SON), the effects of GABAB agonist and antagonist on the firing rate of spontaneous action potentials were studied in SON slice preparations of rats by extracellular recordings. In the presence of the gamma-amino butyric acid (GABA)-gated chloride channel blocker, picrotoxin, the selective GABAB agonist, baclofen, reduced the firing rate of action potentials in both phasic and non-phasic neurons in a dose-dependent manner. The reduction in the firing rate induced by baclofen was reversed by the selective GABAB antagonist, 2-hydroxy saclofen (2OH-saclofen), also in a dose-dependent manner. In non-phasic neurons, 2OH-saclofen significantly increased the firing rate and the effect was additive to the effect of picrotoxin. In phasic neurons, 2OH-saclofen alone did not increase the firing rate, but it reversed suppression of the firing induced by increasing extracellular Ca2+ concentration to 2.1 mM. Baclofen also reduced the firing rate of non-phasic neurons of virgin and lactating female rats, indicating that the GABAB receptor-mediated inhibition is not confined to SON neurons of male rats. The evidence indicates that activation of GABAB receptors inhibits electrical activity of SON neurons of both male and female rats and that GABAB receptors may play an important role in the inhibitory regulation of the electrical activity of SON neurons by GABA.

Topics: 6-Cyano-7-nitroquinoxaline-2,3-dione; Action Potentials; Animals; Baclofen; Dizocilpine Maleate; Excitatory Amino Acid Antagonists; Female; GABA Agonists; GABA Antagonists; In Vitro Techniques; Male; Neural Inhibition; Picrotoxin; Rats; Rats, Wistar; Receptors, GABA-B; Supraoptic Nucleus

We examined the involvement of the GABAB receptor in central respiratory mechanisms. Respiratory neurons (RNs) from the ventral respiratory group in the medulla of the cat were subjected to iontophoretic applications of the GABAB receptor agonist baclofen and the antagonists saclofen and CGP 35348. In all types of RNs baclofen decreased the firing rate. This reduction was antagonized by CGP 35348. Application of either antagonist increased the spontaneous discharge in both inspiratory and expiratory RNs. CGP 35348 excited 57% of the neurons tested, on the average by 34% with ejection currents of 100 nA. Saclofen excited 6 of 9 neurons tested. Baclofen administered systemically (8-12 mg/kg i.v.) to either anesthetized, decerebrate or intact freely moving cats, induced a selective lengthening of the inspiratory phase, an effect comparable to the apneusis induced by the NMDA antagonist MK-801. Baclofen also produced either a pronounced decrease in the amplitude of phrenic nerve discharge or an apnea, both of which were reversed by increasing paCO2. The results suggest that endogenously released GABA acting on GABAB receptors may be involved in the control of respiratory neuronal discharge.

Topics: Animals; Baclofen; Cats; Decerebrate State; Dizocilpine Maleate; Evoked Potentials; Extracellular Space; GABA-A Receptor Antagonists; gamma-Aminobutyric Acid; Iontophoresis; Medulla Oblongata; Nerve Net; Organophosphorus Compounds; Plethysmography; Receptors, GABA-A; Respiration