David A. Johnson, Ph.D.Division Head of Pharmaceutical Sciences and Associate Professor of Pharmacology and Toxicology
Mylan School of Pharmacy
411 Mellon Hall
Education:Ph.D., Pharmacology, Mass. College of Pharmacy & A.H.S., 1990
M.S., Pharmacology, Mass. College of Pharmacy & A.H.S., 1986
B.A., Biology, Hofstra University, 1974
Since coming to Duquesne in 1992, the primary focus of my scholarship has been the role of acetylcholine (ACh) in memory function and the investigation of novel approaches for enhancing memory via the facilitation of central cholinergic neurotransmission. In particular, my laboratory investigated:
1. The effects of caffeine and choline on the release of ACh in the hippocampus and associated reversal of pharmacologically induced memory impairments in male rats.
2.The effects of estrogen supplementation on ACh release and memory function in ovariectomized female rats.
3. The effects of the neurosteroid dehydroepiandrosterone sulfate (DHEAS) and steroid sulfatase inhibitors on cholinergic neurotransmission and memory in male rats.
4. The role of cholinergic neurons that project from the medial septum of the basal forebrain to the hippocampus on memory and other cognitive functions in male and female rats.
The above research was initially funded by internal grants from the university, then small grants from industry and organizations such as Proctor & Gamble Pharmaceuticals and the Hunkle Foundation. Later research was funded by substantial grants from the National Institutes of Health. My laboratory is one of only three in the Myaln School of Pharmacy to receive a prestigious -RO-1- award. One outcome from these studies was the award of two patents for drugs that demonstrated potential as memory enhancers.
Primary insights gained from these studies include:
1. The administration of the synthetic precursor for ACh, choline in combination with the adenosine antagonist caffeine enhances not only ACh release, but facilitates memory in rats.
2. Estrogen and agonists that act at estrogen receptors such as Raloxifine enhance both ACh release and memory function in ovariectomized female rats.
3. Steroid sulfatase inhibitors can facilitate memory in rats impaired by amnestic agents, but potentiates memory impairment in rats with selective lesion of the septal-hippocampal cholinergic tract.
4. For rats with selective lesion of the cholinergic component of the septal-hippocampal tract, impairment in certain working memory tasks is not related to memory loss per se, but delays in shifts to more efficient strategies for navigating a maze.
Taken together, the findings of these studies suggest that drugs and hormones that enhance cholinergic function can facilitate memory. However, a cholinergic tract that had earlier been identified as having a central role in memory in fact plays a smaller part in this function. Nonetheless, we discovered that the cholinergic component of the septal-hippocampal tract is important for other cognitive functions such as strategy selection.
In addition to continuing research on memory, I have also overseen research in a different area, the effect of concentrated platelets on bone healing following tooth extraction. The expected outcome from this research will be an increase in the use of protein rich plasma in clinical dental practice.
My research has been funded by grants without interruption since 1992 for a total of over $800,000. Among these were awards totaling over $700,00 from highly competitive agencies such as the National Institutes of Health and the American Association of Colleges of Pharmacy that typically fund fewer than 20% of proposals received.
Since coming to Duquesne, I have taught a number of classes in both the professional programs of the Mylan School of Pharmacy and the Graduate School of Pharmaceutical Sciences. My philosophy of teaching is to facilitate learning by emphasizing basic concepts rather than minor factual details that are not retained, placing topics within context by using real life examples, and maximizing retention via active learning techniques including the Socratic method, writing exercises and computerized interactive testing programs.
During my years at Duquesne I have developed and introduced a number of new courses into both the Professional and Graduate Curricula:
Health Care and Religion: The intent of this team taught course is give Pharmacy students insights into a patient's/customer's religion affects how they relate to medical care and drug therapy.
Drug Action, Design and Delivery: The goal of this course is to provide exposure to the graduate students of one of the disciplines in the Pharmaceutical Sciences with foundational concepts in the other disciplines. This provides the students with a better understanding of how their research fits in and impacts research in the other disciplines.
Neuronal Biochemistry: This course is intended to give Pharmacology students specializing in Neuropharmacology an understanding of how neurons synthesize release and degrade the various classes of neurotransmitters and how those transmitters affect post-synaptic neurons via receptor binding to produce a particular effect.
Neuronal Pharmacology and General Toxicological Principles: The intent of the course is to survey the pharmacological mechanisms of various drug classes that affect the peripheral and central nervous systems. A second goal is to examine effects of toxicants from the perspective of mechanism(s) of action at the cellular and molecular level.