Specific inhibitory synapses shift the balance from feedforward to feedback inhibition of hippocampal CA1 pyramidal cells.

Feedforward and feedback inhibition are two fundamental modes of operation widespread in the nervous system. We have functionally identified synaptic connections between rat CA1 hippocampal interneurons of the stratum oriens (SO) and interneurons of the stratum lacunosum moleculare (SLM), which can act as feedback and feedforward interneurons, respectively. The unitary inhibitory postsynaptic currents (uIPSCs) detected with K-gluconate-based patch solution at -50 mV had an amplitude of 20.0 +/- 2.0 pA, rise time 2.2 +/- 0.2 ms, decay time 25 +/- 2.2 ms, jitter 1.4 +/- 0.2 ms (average +/- SEM, n = 39), and were abolished by the gamma-aminobutyric acid (GABA)(A) receptor antagonist 2-(3-carboxypropyl)-3-amino-6-methoxyphenyl-pyridazinium bromide (SR 95531). Post hoc anatomical characterization revealed that all but one of the identified presynaptic neurons were oriens-lacunosum moleculare (O-LM) cells, whereas the postsynaptic neurons were highly heterogeneous, including neurogliaform (n = 4), basket (n = 4), Schaffer collateral-associated (n = 10) and perforant path-associated (n = 9) cells. We investigated the short-term plasticity expressed at these synapses, and found that stimulation at 10-40 Hz resulted in short-term depression of uIPSCs. This short-term plasticity was determined by presynaptic factors and was not target-cell specific. We found that the feedforward inhibition elicited by the direct cortical input including the perforant path onto CA1 pyramidal cells was modulated through the inhibitory synapses we have characterized. Our data show that the inhibitory synapses between interneurons of the SO and SLM shift the balance between feedback and feedforward inhibition onto CA1 pyramidal neurons

Comparative study of commercially available anti-alpha-synuclein antibodies.

Immunohistochemistry for alpha-synuclein has become the histological technique of choice for the diagnosis for Parkinson's disease, Dementia with Lewy bodies and Multiple System Atrophy (http://www.ICDNS.org). Nevertheless, no standardised protocol has been proposed. We have reviewed 242 of the 270 studies published until June 2005 that mentioned immunohistochemistry for anti-alpha synuclein on human tissue and we found that only 75 (31%) used commercial antibodies. We also noted that protocols, particularly dilution and antigen unmasking, varied between studies, even when the same antibody was employed. In order to establish a standardised protocol for alpha-synuclein immunohistochemistry, which can be applied in diagnostic neuropathology we tested seven commercial monoclonal antibodies in brains of subjects with Parkinson's disease, dementia with Lewy bodies, multiple system atrophy, multiple sclerosis with incidental Lewy bodies and aged-matched normal brain and determined for each antibody the best suited protocol for antigen unmasking. We evaluated the intensity of immunolabelling in Lewy bodies, neuropil threads, dendrites, pre-synaptic terminals, granular cytoplasmic positivity, peri-axonal positivity, glial inclusions and non-specific immunolabelling. Although our results showed that all the antibodies detected alpha-synuclein inclusions, differences were noted between antibodies, particularly with regard to the detection of glial inclusions. From our study, the best antibodies of the seven tested appeared to be those directed against amino acids 116-131 and 15-123 and we suggest them to be used in routine diagnostic practice for alpha-synucleinopathies

Slow GABA transient and receptor desensitization shape synaptic responses evoked by hippocampal neurogliaform cells.

The kinetics of GABAergic synaptic currents can vary by an order of magnitude depending on the cell type. The neurogliaform cell (NGFC) has recently been identified as a key generator of slow GABA(A) receptor-mediated volume transmission in the isocortex. However, the mechanisms underlying slow GABA(A) receptor-mediated IPSCs and their use-dependent plasticity remain unknown. Here, we provide experimental and modeling data showing that hippocampal NGFCs generate an unusually prolonged (tens of milliseconds) but low-concentration (micromolar range) GABA transient, which is responsible for the slow response kinetics and which leads to a robust desensitization of postsynaptic GABA(A) receptors. This strongly contributes to the use-dependent synaptic depression elicited by various patterns of NGFC activity including the one detected during theta network oscillations in vivo. Synaptic depression mediated by NGFCs is likely to play an important modulatory role in the feedforward inhibition of CA1 pyramidal cells provided by the entorhinal cortex