Impaired lactate release in dCA1 astrocytes contributed to nociceptive sensitization and comorbid memory deficits in rodents
Shuang Han, Bin Jiang, Jiale Ren, Feng Gao, Junjian Wen, Taihe Zhou, Laijian Wang, Xuhong Wei- Anesthesiology and Pain Medicine
Background
Memory deficits are a common comorbid disorder in patients suffering from neuropathic pain. The mechanisms underlying the comorbidities remain elusive. We hypothesized that impaired lactate release from dysfunctional astrocytes in dorsal hippocampal CA1 contributed to memory deficits.
Methods
A spared nerve injury model was established to induce both pain and memory deficits in rats and mice of both sexes. Von Frey tests, novel object recognition and conditioned place preference tests were applied to evaluate the behaviors. Whole-cell recording, fiber photometry, Western blotting, and immunohistochemistry combined with intracranial injections were used to explore the underlying mechanisms.
Results
Animals with spared sciatic nerve injury that had displayed nociception sensitization/memory deficit comorbidities demonstrated a reduction in the intrinsic excitability of pyramidal neurons, accompanied by reduced Ca 2+ activation in astrocytes (ΔF/F, sham: 6±2%; comorbidity: 2±0.4%), and a decrease in the expression of glial fibrillary acidic protein and lactate levels in the dorsal CA1. Exogenous lactate supply or increasing endogenous lactate release by chemogenetic activation of astrocytes alleviated this comorbidity by enhancing the cell excitability (129±4 vs. 88 ± 10 for 3.5 mM lactate) and potentiating N-methyl-D-aspartate receptor-mediated excitatory postsynaptic potentials of pyramidal neurons. In contrast, inhibition of lactate synthesis, blocking lactate transporters, or chemogenetic inhibition of astrocytes resulted in comorbidity-like behaviors in naive animals. Notably, β2-adrenergic receptors in astrocytes but not neurons were downregulated in dorsal CA1 after spared nerve injury. Microinjection of a β2 receptor agonist into dorsal CA1 or activation of the noradrenergic projections onto the hippocampus from locus coeruleus, alleviated the comorbidity, possibly by increasing lactate release.
Conclusions
Impaired lactate release from dysfunctional astrocytes, which could be rescued by activation of locus coeruleus, led to nociception/memory deficits following peripheral nerve injury.