Injection of colchicine intra-hippocampal cortical area 1 enhances novelty seeking behavior

Objective: Colchicine, a potent neurotoxin derived of plant has been recently identified as a degenerative toxin of small pyramidal cells in the hippocampal cortical area 1 (CA1). In this study, the effect of the alkaloid intra hippocampal CA1 on the novelty seeking behavior in the conditioning task was measured. Materials and Methods: Injections of colchicine (1-75 μg/rat, intra-CA1) were performed in cannulated male Wistar rats while being settled in the stereotaxic apparatus. Control group was solely injected saline (1 μl/rat, intra-CA1). One week later, after recovery, all the animals passed the novelty seeking paradigm using an unbiased conditioning task. They were habituated with the conditioned place preference (CPP) apparatus on day 1. Then they were confined in one part of the CPP box for 3 more days. Finally, the animals were tested in the last day. To evaluate, the possible cell injury effect of the toxin on the pyramidal cells of the CA1 both the motivational staying signal in the parts of the box and the non-motivational locomotive signs of the rats were measured. Results: Based on the present study, the alkaloid caused significant novelty seeking behavior at higher doses. It also affected the compartment entering behavior in the colchicine received group. However, the alkaloid did not show the significant effect on sniffing, rearing or grooming in the rats. Conclusion: Injection of colchicine intra-CA1 may impair the neuronal transmission of motivational information by the pyramidal cells in the dorsal hippocampus.