Perineuronal nets (PNNs) are aggregations of extracellular matrix associated with specific neuronal populations in the central nervous system, suggested to play key roles in neural development, synaptogenesis and experience-dependent synaptic plasticity. pregnancy and lactation are characterized by a dramatic increase in neuroplasticity. However, dynamic changes in the extracellular matrix associated with maternal circuits have been mostly overlooked. We analyzed the structure of pnns in an essential nucleus of the maternal circuit, the medial preoptic area (mpoA), during the reproductive cycle of rats, using the Wisteria floribunda (WfA) label. pnns associated to neurons in the mpoA start to assemble halfway through gestation and become highly organized prior to parturition, fading through the postpartum period. this high expression of pnns during pregnancy appears to be mediated by the influence of estrogen, progesterone and prolactin, since a hormonal simulatedgestation treatment induced the expression of pnns in ovariectomized females. We found that pnns associated neurons in the mpoA express estrogen receptor α and progesterone receptors, supporting a putative role of reproductive hormones in the signaling mechanisms that trigger the assembly of PNNs in the mPOA. This is the first report of PNNs presence and remodeling in mPOA during adulthood induced by physiological variables.

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The presence of Myosin Va (an actin-based molecular motor) in the peripheral nervous system was examined and its subcellular distribution within the axons of the sciatic nerve was demonstrated via immunocytochemistry. Myosin Va (M-Va) in the nerve was detected by using SDS-PAGE and Western blot techniques with a polyclonal antibody specifically raised against the M-Va globular tail domain. In addition, purification of M-Va from the rat sciatic nerve prior to immunoblotting yielded a M-Va standard band. Likewise, optical immunocytochemical procedures revealed the presence of M-Va, particularly in the cortical axoplasmic territory, but also in the Schwann cell soma. The above experiments were carried out both on intact as well as on severed sciatic nerves with similar results. The proximal stumps of severed sciatic nerves (from 0 to 72 h after injury) were labelled in vivo with (35)S-methionine. SDS-PAGE autoradiography of the immunoabsorbed M-Va from the radiolabelled homogenized nerve tissue showed a significant increment of the radioactive intensity of M-Va heavy chain band through time. Moreover, a significant increment of transcripts coding for M-Va heavy chain was detected through time using RT-PCR after nerve injury and compared to intact nerves. This data suggest that M-Va is up-regulated in a time-dependent manner. The latter suggests a possible involvement of M-Va in nerve regeneration processes.

Segmenting self- from allo-generated signals is crucial for active sensory processing. We report a dynamic filter used by South American pulse electric fish to distinguish active electro-sensory signals carried by their own electric discharges from other concomitant electrical stimuli (i.e. communication signals). The filter has a sensory component, consisting of an onset type central electro-sensory neuron, and a motor component, consisting of a change in the fish's discharge rate when allo-generated electrical events occur in temporal proximity to the fish's own discharge. We investigated the sensory component of the filter by in vitro mimicking synaptic inputs occurring during behavioral responses to allo-generated interfering signals. We found that active control of the discharge enhances self-generated over allo-generated responses by forcing allo-generated signals into a central refractory period. This hypothesis was confirmed by field potential recordings in freely discharging fish. Similar sensory-motor mechanisms may also contribute to signal segmentation in other sensory systems.