Presentation on theme: "History of Brain Slices Until the early 1970s,sorting out the mechanism of synaptic transmission relied on a few preparations with large accessible neurons."— Presentation transcript:
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. These two effects reduce zinc release about 75% in vitro, compared to in vivo. 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.