| Long-term changes in neurons are believed to contribute to the formation of long-term memory. These changes include dendritic growth, synaptogenesis, increased protein synthesis, protein kinase activation, and protein phosphorylation. Some of the proteins that are associated with structural changes in cells include neuronal growth-associated protein family (nGAPs, e.g., GAP-43 and superior cervical ganglion-10 (SCG10)), extracellular matrix proteins (e.g., agrin), and the heat shock protein family (e.g., HSC70). These same proteins might also be associated with learning. The hypothesis presented here is that changes in expression levels of gap-43 and hsc70 genes in the rat brain occur with the acquisition and storage of spatial memory. To localize and quantify changes in the levels of gap-43 and hsc70 mRNA expression in the brain during spatial learning we used in situ hybridization, Northern blotting, and Reverse Transcriptase-Polymerase Chain Reaction (RT-PCR). In addition, we used immunoblotting to quantify changes in the levels of the brain's GAP-43 and HSC70 proteins during spatial learning as measured by a rat's performance in a Morris water maze were measured by densitometric analysis of Western blots. Training of animals in the Morris water maze task consisted of 10 trials per day in which the animals were given 60 seconds to find a submerged platform. Rats were trained for either 1, 2, 3, 4, or 5 days and sacrificed 24 h after their final training trial. Results showed significant increases in the levels of gap-43 and hsc70 mRNA with spatial learning. These findings suggest that these two genes may contribute to the neurobiological basis of memory formation. |
