Mice treated with tetrahydrocannabinol (THC) show suppression of long-term potentiation in the hippocampus, a process that is essential for the formation and storage of long-term memory.  These results may concur with anecdotal evidence suggesting that smoking cannabis impairs short-term memory.  Consistent with this finding, mice without the CB receptor show enhanced memory and long-term potentiation indicating that the endocannabinoid system may play a pivotal role in the extinction of old memories. One study found that the high-dose treatment of rats with the synthetic cannabinoid HU-210 over several weeks resulted in stimulation of neural growth in the rats' hippocampus region, a part of the limbic system playing a part in the formation of declarative and spatial memories, but did not investigate the effects on short-term or long-term memory. Taken together, these findings suggest that the effects of endocannabinoids on the various brain networks involved in learning and memory may vary.