Predicting the functional states of human iPSC-derived neurons with single-cell RNA-seq and electrophysiology.

Human neural progenitors derived from pluripotent stem cells develop into electrophysiologically active neurons at heterogeneous rates, which can confound disease-relevant discoveries in neurology and psychiatry. By combining patch clamping, morphological and transcriptome analysis on single-human neurons in vitro, we defined a continuum of poor to highly functional electrophysiological states of differentiated neurons. The strong correlations between action potentials, synaptic activity, dendritic complexity and gene expression highlight the importance of methods for isolating functionally comparable neurons for in vitro investigations of brain disorders. Although whole-cell electrophysiology is the gold standard for functional evaluation, it often lacks the scalability required for disease modeling studies. Here, we demonstrate a multimodal machine-learning strategy to identify new molecular features that predict the physiological states of single neurons, independently of the time spent in vitro. As further proof of concept, we selected one of the potential neurophysiological biomarkers identified in this study-GDAP1L1-to isolate highly functional live human neurons in vitro.

Rapid decay of cocaine-induced behavioral sensitization of locomotor behavior.

Sprague Dawley rats received three daily intraperitoneal (i.p.) injections of saline or 15 mg/kg cocaine. Following an interval of 2, 5 or 8 days, the behavioral response of separate groups of rats to a challenge injection of cocaine (15 mg/kg) was tested in an open field. After repeated cocaine (15 mg/kg) injection, movement in both the vertical and horizontal plane was increased in cocaine-treated rats 2, but not 5 or 8, days after treatment as compared to saline-treated subjects. In addition, behavioral ratings along an ordinal scale designed to reflect increases in behavioral activation were increased in cocaine-treated rats 2, but not 5 or 8, days after treatment. These results stand in contrast to other reports demonstrating long-lasting neural and behavioral changes after similar treatment regimens. Taken together, the results suggest that a treatment regimen of 15 mg/kg per day of cocaine for 3 days produces behavioral sensitization of locomotor behavior; however, this cocaine-induced behavioral sensitization does not persist beyond a few (< 5) days after repeated cocaine treatment, using the current experimental parameters.

(+/-) CPP, an NMDA receptor antagonist, blocks the induction of commissural-CA3 LTP in the anesthetized rat.

Commissural CA3-CA3 (cCA3) long-term potentiation (LTP) was investigated in the anesthetized rat treated with the highly selective NMDA-receptor antagonist D,L-3[(+/-)-2-carboxypiperazin-4-yl]- propyl-1-phosphonic acid (CPP). Intraperitoneal injections of CPP did not significantly affect baseline test responses for either field EPSP slope or amplitude measures but did reduce LTP in a dose-dependent manner, with 3.2 mg/kg as the lowest effective dose. EPSP variability following tetanization was also significantly reduced in both the 3.2 mg/kg and 10.0 mg/kg groups. We interpret these results to suggest that a 3.2 mg/kg dose of CPP may be sufficient for studying the behavioral effects of this NMDA receptor antagonist.

D-Pen2-[D-Pen5]enkephalin impairs acquisition and enhances retention of a one-way active avoidance response in rats.

We reported previously that D-Pen2-[D-Pen5]enkephalin (DPDE), a delta-opioid receptor selective analog of Leu-enkephalin, impairs acquisition of an automated jump-up avoidance response in rats and acquisition of a one-way active avoidance response in mice. In the present study we investigated the effects of DPDPE on one-way avoidance conditioning in rats. The rats received two escape-only trials on day 1 and eight additional training trials on day 2. DPDPE (1.16 micrograms/kg IP) administered prior to training on day 2 impaired acquisition of the avoidance response. On the other hand, DPDPE (0.332 microgram/kg IP) administered following presentation of the two escape-only trials on day 1 significantly enhanced retention, as measured by improved one-way active avoidance performance on day 2. These results indicate that activation of delta-opioid receptors by DPDPE has a modulatory effect on acquisition and retention of aversively motivated performance.