PC-2, LINEAR HOMOGLUCAN WITH ALPHA-LINKAGES, PERIPHERALLY ENHANCES THE HIPPOCAMPAL LONG-TERM POTENTIATION

Purpose. To investigate central effectiveness of PC-2, a glucan from l ichen 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. Methods. The extent of LTP, induced by high-frequency stimulation of medial perforant pathway, was evaluated as fractional increase in popu lation spike amplitude in dentate gyrus in anesthetized rats. Results. Oral and intravenous application of PC-2 resulted in significant enha ncement of LTP elicited by a weak, but not by a strong, tetanic stimul ation. No influence of PC-2 on basal evoked synaptic potential was fou nd. Bilateral adrenalectomy profoundly suppressed the positive impact of the glucan on the formation of LTP, but showed no effect upon the m agnitude and time-course of population spike enhancement in vehicle-tr eated subjects. Two related alpha-glucans with different chemical stru ctures did not show any effect comparable to that of PC-2. Conclusions . Peripheral application of PC-2 significantly enhances LTP in dentate gyrus in rats. Results indicate that the effect of PC-2 might be peri pherally mediated and that the specific higher structure of PC-2 is cr ucial for its biological activity.