Document Type

Thesis

Date of Award

5-1999

School/College

College of Science, Engineering, and Technology (COSET)

Degree Name

MS in Biology

First Advisor

Yvonne Hogan

Abstract

Long-term potentiation is an activity dependent phenomenon that results from the repeated activation of presynaptic elements. Evidence suggests it is a memory-related phenomenon. Long-term potentiation has been mostly studied in hippocampus area of brain. Several investigators have also been demonstrated LTP in rats superior cervical ganglia. The cellular mechanisms involve in the development of LTP in SCG of rat is need of further investigation. From the results of preliminary data, nitric oxide and carbon monoxide appear to be responsible for changes in cellular mechanisms involving various pathways (e.g. cAMP, cGMP,protein kinases.etc). This project was designed to investigate some of these pathways.The method for the induction of LTP was similar used by the early investigators. The LTP was produced by the tetanic stimulation of the preganglionic nerve at 20 pulses/20 seconds (20Hzl20s). Different drugs were used to characterize the different pathway. Our results show that phosphodiesterase inhibitor, dipyridamole (1 Oulvl) and adenylate cyclase inhibitor, SQ 22,536 (10uM) both were failed to inhibit the induction of LTP. The pretreatment of 8- 1 2 Br-cAMP ( ImM) and 8-Br-cGMP (lmM) enhanced the basal transmission. However, when train was applied there were no LTP and PTP in the potentiated ganglia. The posttetanic treatment of8-Br-cAMP enhanced the expression of LTP. To elucidate the role of CO as a retrograde messenger in superior cervical ganglia of rat oxyhemoglobin (lOuM) was used. The pretreatment of Hb prevented the expression of LTP but when train was applied after wash out of oxyhemoglobin LTP was generated. this result shows that effect of Hb was reversible. To find the effect of phenytion on the of SCG of rat, phenytion (40uMO was administrated before and after the train. The drug completely blocked the established LTP. Pretreatment of phenytion inhibited the induction of LTP without affecting the PTP.

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