PC-2, linear homoglucan with α-linkages, peripherally enhances the hippocampal long-term potentiation

To investigate central effectiveness of PC-2, a glucan from lichen Parmelia caperata with alpha(1-3)(1-4) linkages in the ratio 3:2, with regard to the long-term potentiation (LTP) of evoked potential. The extent of LTP, induced by high-frequency stimulation of medial perforant pathway, was evaluated as fractional increase in population spike amplitude in dentate gyrus in anesthetized rats. Oral and intravenous application of PC-2 resulted in significant enhancement of LTP elicited by a weak, but not by a strong, tetanic stimulation. No influence of PC-2 on basal evoked synaptic potential was found. Bilateral adrenalectomy profoundly suppressed the positive impact of the glucan on the formation of LTP, but showed no effect upon the magnitude and time-course of population spike enhancement in vehicle-treated subjects. Two related alpha-glucans with different chemical structures did not show any effect comparable to that of PC-2. Peripheral application of PC-2 significantly enhances LTP in dentate gyrus in rats. Results indicate that the effect of PC-2 might be peripherally mediated and that the specific higher structure of PC-2 is crucial for its biological activity.