The amount of axonally transported proteins in the nervus splanchnicus of cod ( Gadus morhua ) was found to be temperature‐dependent in vitro, with an optimum at 8°C. The transport was markedly reduced at 2°C, probably caused by decreased protein synthesis rather than disassembly of microtubules. Microtubules were isolated from cod brain by cycles of assembly‐disassembly. These microtubules were cold‐labile, had a low amount of microtubule‐associated proteins and a high critical concentration for assembly. The possibilities exist that a cold‐stabilizing factor or cold‐stable microtubules are lost during the preparation, or that cold‐stable microtubules are components of the peripheral axons only.
