Nanoscale channels realized at the conducting interface between LaAlO3 and SrTiO3 provide a perfect playground to explore the effect of dimensionality on the electronic properties of complex oxides. Here we compare the electric transport properties of devices realized using the atomic force microscope-writing technique and conventional photolithography. We find that the lateral size of the conducting paths has a strong effect on their transport behavior at low temperature. We observe a crossover from a metallic to an insulating regime occurring at about 50 K for channels narrower than 100 nm. The insulating upturn can be suppressed by the application of a positive backgate. We compare the behavior of nanometric constrictions in lithographically patterned channels with the result of model calculations, and we conclude that the experimental observations are compatible with the physics of a quantum point contact.