PURPOSE: Modafinil is a wake-promoting agent that has been proposed to improve cognitive performance at the preclinical and clinical levels. Since there is insufficient evidence for modafinil to be regarded as a cognitive enhancer, the aim of this study was to investigate the effects of chronic modafinil administration on behavioral learning in healthy adult rats. METHODS: Y-maze training was used to assess learning performance, and the whole-cell patch clamp technique was used to assess synaptic transmission in pyramidal neurons of the hippocampal CA1 region of rats. RESULTS: Intraperitoneal administration of modafinil at 200 mg/kg or 300 mg/kg significantly improved learning performance. Furthermore, perfusion with 1mM modafinil enhanced the frequency and amplitude of spontaneous postsynaptic currents and spontaneous excitatory postsynaptic currents in CA1 pyramidal neurons in hippocampal slices. However, the frequency and amplitude of spontaneous inhibitory postsynaptic currents in CA1 pyramidal neurons were inhibited by treatment with 1mM modafinil. CONCLUSIONS: These results indicate that modafinil improves learning and memory in rats possibly by enhancing glutamatergic excitatory synaptic transmission and inhibiting GABAergic (gamma-aminobutyric acid-ergic) inhibitory synaptic transmission.
Adult ; Animals ; CA1 Region, Hippocampal ; Excitatory Postsynaptic Potentials ; Humans ; Inhibitory Postsynaptic Potentials ; Learning* ; Memory ; Neurons ; Perfusion ; Rats* ; Synaptic Potentials ; Synaptic Transmission*

AIMTo investigate the effects of morphine on synaptic transmission of neurons of central nervous system and reveal the mechanism underlying it.

METHODSNew born wistar rats were used for primary culture of hippocampus neurons. Using whole-cell patch-clamp technique, we observed the excitatory and spontaneous inhibitory postsynaptic current (EPSC, sIPSC) and glutamate-induced current before and after morphine treatment.

RESULTS(1) sEPSC of hippocampal neurons was markedly increased after morphine application. The effect of morphine was blocked by opioid antagonist naloxone (n=18, P < 0.01). (2) The frequency of mEPSC and the amplitude of glutamate-induced current of hippocampal neurons had no significant changes after morphine treatment (P > 0.05). (3) Morphine inhibited sIPSC of hippocampal neurons markedly and naloxone could block this effect (n=13, P < 0.01).

CONCLUSIONThe results suggest that the exciting effect of morphine on hippocampal neurons are not due to direct influence of morphine on glutamate synapses transmission, but may result from the inhibition on interneurons, that is "disinhibition" way.

Animals ; Animals, Newborn ; Cells, Cultured ; Excitatory Postsynaptic Potentials ; physiology ; Hippocampus ; cytology ; Inhibitory Postsynaptic Potentials ; Morphine ; pharmacology ; Neurons ; drug effects ; physiology ; Patch-Clamp Techniques ; Rats ; Rats, Wistar ; Synaptic Transmission ; drug effects ; physiology

The medial vestibular nucleus (MVN) neurons are controlled by excitatory synaptic transmission from the vestibular afferent and commissural projections, and by inhibitory transmission from interneurons. Spontaneous synaptic currents of MVN neurons were studied using whole cell patch clamp recording in slices prepared from 13- to 17-day-old rats. The spontaneous inhibitory postsynaptic currents (sIPSCs) were significantly reduced by the GABAA antagonist bicuculline (20micrometer), but were not affected by the glycine antagonist strychnine (1micrometer). The frequency, amplitude, and decay time constant of sIPSCs were 4.3 0.9 Hz, 18.1 2.0 pA, and 8.9 0.4 ms, respectively. Spontaneous excitatory postsynaptic currents (sEPSCs) were mediated by non-NMDA and NMDA receptors. The specific AMPA receptor antagonist GYKI-52466 (50micrometer) completely blocked the non-NMDA mediated sEPSCs, indicating that they are mediated by an AMPA-preferring receptor. The AMPA mediated sEPSCs were characterized by low frequency (1.5 0.4 Hz), small amplitude (13.9 1.9 pA), and rapid decay kinetics (2.8 0.2 ms). The majority (15/21) displayed linear I-V relationships, suggesting the presence of GluR2-containing AMPA receptors. Only 35% of recorded MVN neurons showed NMDA mediated currents, which were characterized by small amplitude and low frequency. These results suggest that the MVN neurons receive excitatory inputs mediated by AMPA, but not kainate, and NMDA receptors, and inhibitory transmission mediated by GABAA receptors in neonatal rats.
alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid ; Animals ; Bicuculline ; Excitatory Postsynaptic Potentials* ; Glycine ; Inhibitory Postsynaptic Potentials ; Interneurons ; Kainic Acid ; Kinetics ; N-Methylaspartate ; Neurons* ; Rats* ; Receptors, AMPA ; Receptors, N-Methyl-D-Aspartate ; Strychnine ; Synaptic Transmission ; Vestibular Nuclei*

Following peripheral nerve injury, excessive nociceptive inputs result in diverse physiological alterations in the spinal cord substantia gelatinosa (SG), lamina II of the dorsal horn. Here, I report the alterations of excitatory or inhibitory transmission in the SG of a rat model for neuropathic pain ("spared nerve injury"). Results from whole-cell recordings of SG neurons show that the number of distinct primary afferent fibers, identified by graded intensity of stimulation, is increased at 2 weeks after spared nerve injury. In addition, short-term depression, recognized by paired-pulse ratio of excitatory postsynaptic currents, is significantly increased, indicating the increase of glutamate release probability at primary afferent terminals. The peripheral nerve injury also increases the amplitude, but not the frequency, of spontaneous inhibitory postsynaptic currents. These data support the hypothesis that peripheral nerve injury modifies spinal pain conduction and modulation systems to develop neuropathic pain.
Animals ; Depression ; Excitatory Postsynaptic Potentials ; Glutamic Acid ; Horns ; Inhibitory Postsynaptic Potentials ; Models, Animal ; Neuralgia ; Neurons ; Patch-Clamp Techniques ; Peripheral Nerve Injuries* ; Peripheral Nerves* ; Rats* ; Spinal Cord* ; Substantia Gelatinosa* ; Synaptic Transmission*

Isoliquiritigenin (ILTG) is a chalcone compound and shows various pharmacological properties, including antioxidant and anti-inflammatory activities. In recent study, we have reported a novel role of ILTG in sleep through a positive allosteric modulation of gamma-aminobutyric acid type A (GABA(A))-benzodiazepine (BZD) receptors. However, the effect of ILTG in GABA(A)R-mediated synaptic response in brain has not been tested yet. Here we report that ILTG significantly prolonged the decay of spontaneous inhibitory postsynaptic currents (sIPSCs) mediated by GABA(A)R in mouse hippocampal CA1 pyramidal neurons without affecting amplitude and frequency of sIPSCs. This enhancement was fully inhibited by flumazenil (FLU), a specific GABA(A)-BZD receptor antagonist. These results suggest a potential role of ILTG as a modulator of GABAergic synaptic transmission.
Animals ; Brain ; Chalcone* ; Flumazenil ; gamma-Aminobutyric Acid ; Inhibitory Postsynaptic Potentials ; Mice ; Neurons ; Synaptic Transmission

Previous studies have suggested that brain stem noradrenergic inputs differentially modulate neurons in the paraventricular nucleus (PVN). Here, we compared the effects of norepinephrine (NE) on spontaneous GABAergic inhibitory postsynaptic currents (sIPSCs) in identified PVN neurons using slice patch technique. In 17 of 18 type I neurons, NE (30-100microM) reversibly decreased sIPSC frequency to 41+/-7% of the baseline value (4.4+/-0.8 Hz, p<0.001). This effect was blocked by yohimbine (2-20microM), an alpha2-adrenoceptor antagonist and mimicked by clonidine (50 microM), an alpha2-adrenoceptor agonist. In contrast, NE increased sIPSC frequency to 248+/-32% of the control (3.06+/-0.37 Hz, p<0.001) in 31 of 54 type II neurons, but decreased the frequency to 41+/-7% of the control (5.5+/-1.3 Hz) in the rest of type II neurons (p<0.001). In both types of PVN neurons, NE did not affect the mean amplitude and decay time constant of sIPSCs. In addition, membrane input resistance and amplitude of sIPSC of type I neurons were larger than those of type II neurons tested (1209 vs. 736 M omega, p<0.001; 110 vs. 81 pS, p<0.001). The results suggest that noradrenergic modulation of inhibitory synaptic transmission in the PVN decreases the neuronal excitability in most type I neurons via alpha2-adrenoceptor, however, either increases in about 60% or decreases in 40% of type II neurons.
Brain Stem ; Clonidine ; Inhibitory Postsynaptic Potentials* ; Membranes ; Neurons ; Norepinephrine ; Paraventricular Hypothalamic Nucleus* ; Synaptic Transmission ; Yohimbine

The technique of extracellular recording was used and the changes in the slope of field excitatory postsynaptic potential (S-EPSP) and the amplitude of population spike (A-PS) were observed when homosynaptic long-term depression (LTD) was induced by low-frequency stimulation (LFS) in the CA1 region of rat hippocampal slices. After LFS of 900 pulses at 1 Hz was delivered, S-EPSP and A-PS were reduced by 35.4 +/- 5.3% and 68.0 +/- 7.2%, respectively. When LFS of 450 pulses at 1 Hz was delivered, S-EPSP and A-PS were reduced by 14.3 +/- 2.3% and 36.8 +/- 6.7%, respectively. In both groups, the change in A-PS was significantly greater than that in S-EPSP (P<0.01). The changes in both indexes in the group of 900 pulses were greater than those in the group of 450 pulses (P<0.05). High Mg(2+) (4 mmol/L) could attenuate the synaptic transmission, but did not affect the induction of LTD. In the high Mg(2+) medium, the change in A-PS induced by LFS was also markedly greater than that in S-EPSP (P<0.01). These results indicate that the level of homosynaptic LTD induced by LFS is dependent not only on the numbers of pulses of LFS delivered, but also on the selection of evaluating index.
Animals ; Electric Stimulation ; Excitatory Postsynaptic Potentials ; physiology ; Hippocampus ; physiology ; In Vitro Techniques ; Long-Term Synaptic Depression ; Male ; Rats ; Rats, Sprague-Dawley ; Synaptic Transmission ; physiology

The aim of the present study is to observe the receptor kinetics property of long-term potentiation (LTP) of excitatory postsynaptic potential (EPSP) in spinal cord motoneurons (MNs) by descending activation. The intracellular recording techniques were conducted in spinal cord MNs of neonatal rats aged 8-14 days. The changes of EPSP induced by ipsilateral ventrolateral funiculus (iVLF) stimulation (iVLF-EPSPs) were observed, and receptor kinetics of iVLF-EPSPs were analyzed. The results showed that, the amplitude, area under curve and maximum left slope of EPSP were positively correlated with stimulus intensity (P < 0.05 or P < 0.01), while the apparent receptor kinetic parameters apparent dissociation rate constant (K(2)), apparent equilibrium dissociation constant (K(T)) of EPSP were negatively correlated with stimulus intensity (P < 0.01 or P < 0.05). The iVLF-EPSPs were persistently increased after tetanic stimulation (100 Hz, 50 pulses/train, duration 0.4-1.0 ms, 6 trains, main interval 10 s, 10-100 V) in 5 of 11 tested MNs. The amplitude of iVLF-EPSPs was potentiated to more than 120% of baseline and lasted at least 30 min, which could be referred to as iVLF-LTP. Meanwhile, the area under curve and maximum left slope of EPSPs were also increased to more than 120% of baseline. During iVLF-LTP, apparent receptor kinetics analyses of iVLF-EPSPs indicated that K(2) and KT were decreased significantly to less than 80% of the baseline within 10 min and gradually and partially recovered in 3 MNs. These results of receptor kinetics analyses of iVLF-EPSPs suggest a possible enhancement in affinity of postsynaptic receptors in the early stage of iVLF-LTP in some MNs.
Animals ; Excitatory Postsynaptic Potentials ; Kinetics ; Long-Term Potentiation ; Motor Neurons ; physiology ; Rats ; Spinal Cord ; cytology ; Synaptic Transmission

In the present experiments, the characteristics of the electrical responses to stimulation of the cerebellum in crucian carp Mauthner cell were explored with microeletrode intracellular recording technique. A composite excitatory postsynaptic potential (cerebellum-evoked EPSP) could be induced from the soma, the ventral dendrite and the proximal end of the lateral dendrite in crucian carp Mauthner cell (M-cell) on either side by stimulation of the ventrolateral region of the cerebellum. The cerebellum-evoked EPSP presented characteristics of relatively short latency (0.63+/-0.09 ms), longer duration (5.49+/-1.13 ms), graded amplitude and dependence on stimulation frequency. Stimulation of the cerebellum with higher intensity always activated the M-cell orthodromically. Multiple intracellular recordings showed that the cerebellum-evoked EPSP originated in the distal end of the ventral dendrite. The results suggest that the cerebellum-M-cell pathway is probably composed of a group of neuron chains with different numbers of synaptic relays projecting to the distal end of the ventral dendrite in order of length of the chains.
Animals ; Carps ; physiology ; Cerebellum ; physiology ; Dendrites ; physiology ; Electric Stimulation ; Excitatory Postsynaptic Potentials ; physiology ; Neurons ; physiology ; Synapses ; physiology ; Synaptic Transmission ; physiology

Fluoxetine, widely used for the treatment of depression, is known to be a selective serotonin reuptake inhibitor (SSRI), however, there are also reports that fluoxetine has direct effects on several receptors. Employing whole-cell patch clamp techniques in rat brain slice, we studied the effects of fluoxetine on corticostriatal synaptic transmission by measuring the change in spontaneous excitatory postsynaptic currents (sEPSC). Acute treatment of rat brain slice with fluoxetine (10microM) significantly decreased the amplitude of sEPSC (84.1+/-3.3%, n=7), but did not alter its frequency (99.1+/-4.7%, n=7). Serotonin (10microM) also significantly decreased the amplitude (81.2+/-3.9%, n=4) of sEPSC, but did not affect its frequency (105.8+/-8.0, n=4). The effect of fluoxetine was found to have the same trend as that of serotonin. We also found that the inhibitory effect of fluoxetine on sEPSC amplitude (93.0+/-1.9%, n=8) was significantly blocked, but not serotonin (84.3+/-1.6%, n=4), when the brain slice was incubated with p-chloroamphetamine (10microM), which depletes serotonin from the axon terminals and blocks its reuptake. These results suggest that fluoxetine inhibits corticostriatal synaptic transmission through postsynaptic, and that these effects are exerted through both serotonin dependent and independent mechanism.
Animals ; Brain ; Depression ; Excitatory Postsynaptic Potentials ; Fluoxetine* ; p-Chloroamphetamine ; Patch-Clamp Techniques ; Presynaptic Terminals ; Rats ; Serotonin ; Synaptic Transmission*