Volatile anesthetics rapidly increase dendritic spine density in the rat medial prefrontal cortex during synaptogenesis.
BACKGROUND
Recent experimental observations suggest that, in addition to induce neuroapoptosis, anesthetics can also interfere with synaptogenesis during brain development. The aim of this study was to pursue this issue by evaluating the exposure time-dependent effects of volatile anesthetics on neuronal cytoarchitecture in 16-day-old rats, a developmental stage characterized by intense synaptogenesis in the cerebral cortex.


METHODS
Whistar rats underwent isoflurane (1.5%), sevoflurane (2.5%), or desflurane (7%) anesthesia for 30, 60, and 120 min at postnatal day 16, and the effect of these treatments on neuronal cytoarchitecture was evaluated 6 h after the initiation of anesthesia. Cell death was assessed using Fluoro-Jade B staining and terminal deoxynucleotidyl transferase deoxyuridine triphosphate nick-end labeling assay. Ionotophoretic injections into layer 5 pyramidal neurons in the medial prefrontal cortex allowed visualization of dendritic arbor. Tracing of dendritic tree was carried out using the Neurolucida station (Microbrightfield, Williston, VT), whereas dendritic spines were analyzed using confocal microscopy.


RESULTS
Up to a 2-h-long exposure, none of the volatile drugs induced neuronal cell death or significant changes in gross dendritic arbor pattern of layer 5 pyramidal neurons in pups at postnatal day 16. In contrast, these drugs significantly increased dendritic spine density on dendritic shafts of these cells. Importantly, considerable differences were found between these three volatile agents in terms of exposure time-dependent effects on dendritic spine density.


CONCLUSIONS
These new results suggest that volatile anesthetics, with different potencies and without inducing cell death, could rapidly interfere with physiologic patterns of synaptogenesis and thus might impair appropriate circuit assembly in the developing cerebral cortex.
Briner
Adrian
A
Department of Anesthesiology, University Hospital of Geneva, Geneva, Switzerland.
De Roo
Mathias
M
Dayer
Alexandre
A
Muller
Dominique
D
Habre
Walid
W
Vutskits
Laszlo
L
D018685:Anesthetics, Inhalation / Q000494:pharmacology*; D000818:Animals; D016923:Cell Death / Q000187:drug effects; D004396:Coloring Agents; D049229:Dendritic Spines / Q000187:drug effects*; D000077335:Desflurane; D005452:Fluoresceins; D007150:Immunohistochemistry; D020287:In Situ Nick-End Labeling; D007478:Iontophoresis; D007530:Isoflurane / Q000031:analogs & derivatives / Q000494:pharmacology; D008738:Methyl Ethers / Q000494:pharmacology; D009930:Organic Chemicals; D017397:Prefrontal Cortex / Q000166:cytology* / Q000187:drug effects / Q000254:growth & development; D017966:Pyramidal Cells / Q000187:drug effects / Q000648:ultrastructure; D051381:Rats; D020318:Rats, Long-Evans; D017208:Rats, Wistar; D000077149:Sevoflurane; D013569:Synapses / Q000187:drug effects*
D018685:Anesthetics, Inhalation; D004396:Coloring Agents; D005452:Fluoresceins; D008738:Methyl Ethers; D009930:Organic Chemicals; C435731:fluoro jade; D000077149:Sevoflurane; D000077335:Desflurane; D007530:Isoflurane