Plasmin-resistant PSD-95 inhibitors resolve effect-modifying drug-drug interactions between alteplase and nerinetide in acute stroke.

Neuroprotection for acute ischemic stroke is achievable with the eicosapeptide nerinetide, an inhibitor of the protein-protein interactions of the synaptic scaffolding protein PSD-95. However, nerinetide is subject to proteolytic cleavage if administered after alteplase, a standard-of-care thrombolytic agent that nullifies nerinetide's beneficial effects. Here, we showed, on the basis of pharmacokinetic data consistent between rats, primates, and humans, that in a rat model of embolic middle cerebral artery occlusion (eMCAO), nerinetide maintained its effectiveness when administered before alteplase. Because of its short plasma half-life, it can be followed by alteplase within minutes without reducing its neuroprotective effectiveness. In addition, the problem of protease sensitivity is solved by substituting cleavage-prone amino acids from their l- to their d-enantiomeric form. Treatment of rats subjected to eMCAO with such an agent, termed d-Tat-l-2B9c, eliminated protease sensitivity and maintained neuroprotective effectiveness. Our data suggest that both the clinical-stage PSD-95 inhibitor nerinetide and protease-resistant agents such as d-Tat-l-2B9c may be practically integrated into existing stroke care workflows and standards of care.

Laminar differences in field potential morphology and long-term potentiation in motor cortex coronal slices from both unstimulated and previously potentiated rats.

We have reported that long-term potentiation (LTP) can be reliably induced in motor cortex of adult, freely moving rats by the application of spaced and repeated high frequency stimulating trains to the white matter. In the present study, we monitored field potentials (FPs) and LTP in both layer II/III and V in coronal slices of motor cortex taken from implanted control and previously potentiated Long-Evans rats. The baseline FP amplitudes were decreased in layer II/III, and the amplitude of small spikes was significantly increased in layer V in slices from previously potentiated rats compared to unpotentiated control rats. In response to high frequency stimulation applied to the slice itself, both implanted control and previously potentiated rats showed similar levels of LTP in layer II/III. LTP could not be induced in layer V. These results show that layer II/III and V respond differently to high frequency stimulation in vitro. In addition, layer II/III responds very differently in slice compared to chronic preparations.

Presynaptic kainate receptors play different physiological roles in mossy fiber and associational-commissural synapses in CA3 of hippocampus from adult rats.

Mossy fiber (MF) and Associational-commissural (Assoc-com) synaptic responses were recorded simultaneously in CA3 from the same hippocampal slice. Low concentrations of Kainate (KA) (50 and 100 nM) reversibly increased the synaptic response and decreased the paired-pulse facilitation (PPF) in the MF synapse, while reversibly decreasing the synaptic response and increasing the PPF in the Assoc-com synapse. The same concentration of KA had no effect on synaptic transmission or the induction and expression of long-term potentiation (LTP) in area CA1. MF LTP partially occluded the effect of KA on MF responses. These results suggest that KARs function as presynaptic autoreceptors in both MF and Assoc-com synapses but play different roles.