Aquaporin-4 (AQP-4) is the predominant water channel in the central nervous system (CNS) and primarily expressed in astrocytes. Astrocytes have been generally believed to play important roles in regulating synaptic plasticity and information processing. However, the role of AQP-4 in regulating synaptic plasticity, learning and memory, cognitive function is only beginning to be investigated. It is well known that synaptic plasticity is the prime candidate for mediating of learning and memory. Long term potentiation (LTP) and long term depression (LTD) are two forms of synaptic plasticity, and they share some but not all the properties and mechanisms. Hippocampus is a part of limbic system that is particularly important in regulation of learning and memory. This article is to review some research progresses of the function of AQP-4 in synaptic plasticity, learning and memory, and propose the possible role of AQP-4 as a new target in the treatment of cognitive dysfunction.
Animals ; Aquaporin 4 ; physiology ; Hippocampus ; physiology ; Humans ; Learning ; Long-Term Potentiation ; Long-Term Synaptic Depression ; Memory ; Neuronal Plasticity

Animals ; Brain ; physiology ; Extinction, Psychological ; physiology ; Humans ; Long-Term Potentiation ; Long-Term Synaptic Depression ; Neural Pathways ; physiology ; Neuronal Plasticity ; Neurons ; physiology ; Receptors, AMPA ; physiology

BACKGROUNDTraumatic brain injury (TBI) often causes cognitive deficits and remote symptomatic epilepsy. Hippocampal regional excitability is associated with the cognitive function. However, little is known about injury-induced neuronal loss and subsequent alterations of hippocampal regional excitability. The present study was designed to determine whether TBI may impair the cellular circuit in the hippocampus.

METHODSForty male Wistar rats were randomized into control (n = 20) and TBI groups (n = 20). Long-term potentiation, extracellular input/output curves, and hippocampal parvalbumin-immunoreactive and cholecystokinin-immunoreactive interneurons were compared between the two groups.

RESULTSTBI resulted in a significantly increased excitability in the dentate gyrus (DG), but a significantly decreased excitability in the cornu ammonis 1 (CA1) area. Using design-based stereological injury procedures, we induced interneuronal loss in the DG and CA3 subregions in the hippocampus, but not in the CA1 area.

CONCLUSIONSTBI leads to the impairment of hippocampus synaptic plasticity due to the changing of interneuronal interaction. The injury-induced disruption of synaptic efficacy within the hippocampal circuit may underlie the observed cognitive deficits and symptomatic epilepsy.

Animals ; Brain Injuries ; physiopathology ; Hippocampus ; physiopathology ; Long-Term Potentiation ; Male ; Neuronal Plasticity ; physiology ; Rats ; Rats, Wistar

Ventral tegmental area (VTA) is an important relay station of signal transmission in the reward system. The plasticity of VTA dopaminergic neurons directly influences actions of other regions of the reward system. Studies concerning the plasticity of VTA dopaminergic neurons focus mainly on synaptic plasticity, while much less attention has been given to the plasticity of intrinsic excitability of the neurons. The aim of the present study was to investigate the effect of high-frequency stimulation (HFS) on the plasticity of excitability of VTA neuron. Whole-cell patch-clamping was performed on VTA dopaminergic neurons in midbrain slices bathed with PTX, AP-5 and CNQX, and HFS was introduced to cell soma. The result showed that, after HFS induction the pharmacologically isolated neurons showed increased input resistance and firing frequency, as well as decreased rheobase. Meanwhile, the steady-state whole-cell current decreased, and the hyperpolarization-activated current (I(h)) decreased. These results suggest that HFS on soma induces a long-term potentiation of excitability in VTA dopaminergic neurons, and the underlying mechanism involves the changes of membrane current.
Animals ; Dopaminergic Neurons ; cytology ; Long-Term Potentiation ; Patch-Clamp Techniques ; Ventral Tegmental Area ; physiology

The physiological functions of endogenous amyloid-β (Aβ), which plays important role in the pathology of Alzheimer's disease (AD), have not been paid enough attention. Here, we review the multiple physiological effects of Aβ, particularly in regulating synaptic transmission, and the possible mechanisms, in order to decipher the real characters of Aβ under both physiological and pathological conditions. Some worthy studies have shown that the deprivation of endogenous Aβ gives rise to synaptic dysfunction and cognitive deficiency, while the moderate elevation of this peptide enhances long term potentiation and leads to neuronal hyperexcitability. In this review, we provide a new view for understanding the role of Aβ in AD pathophysiology from the perspective of physiological meaning.
Humans ; Alzheimer Disease/pathology* ; Amyloid beta-Peptides/metabolism* ; Long-Term Potentiation ; Synaptic Transmission/physiology* ; Hippocampus

In the present research, patch-clamp whole-cell recording was used to study the developmental changes of the internal horizontal synaptic plasticity in layer II/III of rats' primary visual cortices. Pairing stimulation was used to induce long term potentiation (LTP) of neurons in layer II/III from layer II/III and layer IV. The data indicate that: (1) Responses of layer II/III neurons can be evoked independently at II/III-II/III and IV-II/III synapses by horizontal and vertical stimulations; (2) LTP can be induced from neurons in the layer II/III by horizontal tetanic stimulation at II/III-II/III synapses till postnatal day12 (P12, before eyes open); (3) Meanwhile, only short term potentiation (STP) at IV-II/III synapses can be induced by horizontal tetanic stimulation before eyes open; (4) After P12, a robust LTP at IV-II/III synapses can be induced by horizontal tetanic stimulation; (5) At P14, when vertical and horizontal tetanic stimulations were given to the same neuron, the LTP at IV-II/III synapses was weaker than that induced by vertical stimulation alone, suggesting that vertical synaptic modification was negatively regulated by horizontal inputs when two-direction synaptic inputs were presented at the same time; (6) Spontaneous responses of AMPA receptors (AMPARs) in the layer II/III neuron of rats' primary visual cortices are regulated by the development. The frequency of AMPARs-mediated postsynaptic currents was at a low level before eyes open, increased sharply at P12-P14, and slightly decreased after P18. And the amplitude of spontaneous AMPARs currents slowly decreased after P12. The results demonstrated that both the strength of horizontal synaptic modification and the effects of horizontal inputs on the vertical synaptic connection are regulated by the development. II/III-II/III synaptic communication has dual effects on the IV-II/III synapses, which may be involved in a competitive machinery of neural circuitry maturation and the formation of visual function columns.
Animals ; Long-Term Potentiation ; Neuronal Plasticity ; Neurons ; physiology ; Patch-Clamp Techniques ; Rats ; Receptors, AMPA ; physiology ; Synapses ; physiology ; Visual Cortex ; physiology

Long-term potentiation (LTP) can be induced by various tetanic parameters in the mammalian visual cortex. However, little researches have been done on the relationship between the expression of the long-lasting LTP (late phase LTP or L-LTP) lasting more than 3 h and the tetanic parameters. In the present study, the effects of 2 Hz and 100 Hz tetanic parameters on L-LTP of the field potentials were recorded from the layer II/III of the rat visual cortical slices in response to stimulation of the layer IV. As a result, tetanic parameters that had more than 300 pulses reliably induced L-LTP in the postnatal day 15-21 rats. Obviously different L-LTP expressions were induced by 2 Hz and 100 Hz tetani. There was no difference in L-LTP expression induced by the parameters with the same frequency and different total pulses. These data suggest that L-LTPs induced by different frequency parameters may have different induction and maintenance mechanisms; L-LTPs induced by the parameters with the same frequency may have the same mechanisms.
Animals ; Electric Stimulation ; methods ; Long-Term Potentiation ; physiology ; Male ; Rats ; Rats, Sprague-Dawley ; Synaptic Transmission ; physiology ; Visual Cortex ; physiology

Animals ; Corticosterone ; pharmacology ; Hippocampus ; drug effects ; physiology ; In Vitro Techniques ; Long-Term Potentiation ; drug effects ; physiology ; Male ; Rats ; Rats, Wistar

Long-term potentiation (LTP) of C-fiber evoked field potentials in spinal dorsal horn is first reported in 1995. Since then, the mechanisms underlying the long-lasting enhancement in synaptic transmission between primary afferent C-fibers and neurons in spinal dorsal horn have been investigated by different laboratories. In this article, the related data were summarized and discussed.
Animals ; Evoked Potentials ; Long-Term Potentiation ; Nerve Fibers, Unmyelinated ; physiology ; Posterior Horn Cells ; cytology ; Rats, Sprague-Dawley ; Synaptic Transmission

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