Neurotransmitter Mediation Of The Narcotic Effect On Brain Neurons
Abstract
The septum is a cholinergic system whose fibers serve as the pacemaker for hippocampal theta rhythm. Since acetylcholine is the neurotransmitter involved, cholinergic drugs such as atropine and physostigmine should alter the hippocampal F.EG. Atropine leads to desynchronization of the EEG, but physostigmine will restore theta rhythm. Morphine also alters the EEG and perhaps atropine and physostigmine can be used to reverse the effect of morphine on the hippocampal EEG. Six Wistar rats were implanted with bipolar electrodes in the hippocampus, and the electrical activity was monitored from this hippocampal electrode. The signal was filtered once for an EEG between 3-3000 Hz and again to study theta rhythm by preserving the signal between 1-15 Hz. Various drug regimens incorporating morphine, physostigmine and atropine were tested. It was found that morphine causes an increased amplitude of the EEG signal. Physostigmine could reverse the morphine-induced high amplitude activity and restore theta rhythm; but atropine could not desynchronize the theta rhythm caused by physostigmine. The morphine effect may be due to a depletion of acetylcholine in the septum or, if the entorhinal cortex mediates desynchronization, a stimulation of these neurons. Physostigmine reversed the high amplitude affect of morphine because physostigmine inhibits acetylcholinesterase and thereby prevents the breakdown of the few acetylcholine molecules in the synapse. Such action can restore synchrony. Atropine could not reverse the physostigmine effect probably because the atropine molecules could not compete with the large numbers of acetylcholine molecules for the receptor sites.
Description
Program year: 1976/1977Digitized from print original stored in HDR
Citation
Randall, Randy C. (1977). Neurotransmitter Mediation Of The Narcotic Effect On Brain Neurons. University Undergraduate Fellow. Available electronically from https : / /hdl .handle .net /1969 .1 /CAPSTONE -McFaddenD _1995.