Transcript Problems of Conventional Brain Slice Preparations in Research on

History of Brain Slices
• Until the early 1970s,sorting out the mechanism of
synaptic transmission relied on a few preparations
with large accessible neurons such as the squid
giant synapse, the synapses in mammalian
autonomic ganglia and vertebrate neuromuscular
junction.
• In the late 1960s, C. Yamamoto and H. McIlwain
introduced the use of brain slices—thin sections of
living brain tissue that can be maintained in vitro.
Because oxygen and nutrients rapidly diffuse into
sufficiently thin pieces of tissue , the slices remain
viable for many hours.
Where are brain slices from?
• Brain slices have been prepared from almost all
regions of mammalian central nervous system.
• Including: cortex, thalamus, spinal cord,
hypothalamus, and cerebellum.
• The approach is similar in all these area.
Preparation of Brain Slices
• After animal is killed, the brain is rapidly removed
and the area of interest dissected free.
• A variety of devices—tissue chopper,vibrating razor
blades—are used to section tissue into slices about a
half millimeter thick.
• The slices are then placed in a solution of artificial
cerebrospinal fluid(aCSF) in a warm oxygenated
chamber.
• Under these conditions the neurons in the slices
remain alive and electrically active for up to 24 hours.
Advantages
 Tissue slices are thick enough to preserve many
circuits present in s given brain area.
 Stimulating and recording electrodes can be guided
to desired position using a simple dissecting
microscope.
 Intracellular and extracellular recordings are
straightforward and quite stable, since there is no
heartbeat and respiratory movement to disturb the
placement of electrode.
 Slices recording can be combined with other
methods that would also be difficult to employ in
vivo.
Problems of Conventional Brain Slice
Preparations in Research on Zinc Release
• Research on synaptically-released zinc is frequently done in
vitro with acute brain slice preparations.
• But the in vitro hippocampal slice preparation has two major
pitfalls for zinc research.
•First, up to 50% of the synaptic zinc is lost during slice
cutting and/or the first 10 min of slice incubation, with
the losses being most pronounced on the edges of the
slice.
•Second, the release of the remaining zinc from a slice is
substantially depressed (up to 50%) at the low
temperatures (32°C) typically used for brain slice
studies.
• These two effects reduce zinc release about 75% in vitro,
compared to in vivo.