Cortical cup

The cortical cup has been used for many years to monitor changes in transmitter release induced by physiological and pharmacological stimuli (Fig. 4.5). In the past, it was used most commonly to study release of amino acids and acetylcholine. More recently, it has... 

Figure 4.5 The cortical cup. The cup size obviously varies with the animal on which it is used. For the rat, the overall diameter is 6-7 mm and a typical flow rate is 50 pl/min...

Figure 6.8 ACh release and cortical activity. Correlation between acetylcholine release and EEG activity after injections of leptazol (LEPmgkg intravenously) into the urethane anaesthetised rat. ACh was collected in a cortical cup incorporating EEG recording electrodes. Mean values SE, n — 6 (unpublished data, but see Gardner and Webster 1977)...

ATP certainly fulfils the criteria for a NT. It is mostly synthesised by mitochondrial oxidative phosphorylation using glucose taken up by the nerve terminal. Much of that ATP is, of course, required to help maintain Na+/K+ ATPase activity and the resting membrane potential as well as a Ca +ATPase, protein kinases and the vesicular binding and release of various NTs. But that leaves some for release as a NT. This has been shown in many peripheral tissues and organs with sympathetic and parasympathetic innervation as well as in brain slices, synaptosomes and from in vivo studies with microdialysis and the cortical cup. There is also evidence that in sympathetically innervated tissue some extracellular ATP originates from the activated postsynaptic cell. While most of the released ATP comes from vesicles containing other NTs, some... 

In addition to the loss of GAD staining (i.e. GABA) neurons and inhibitory symmetrical synapses around an alumina focus in primates (see above), studies with a chronically implanted cortical cup over a cobalt lesion (focus) in rats show an increased release of glutamate that is associated with spiking (Dodd and Bradford 1976). 

Glutamate Cerebral cortex In vivo cortical cup technique O Regan et al. 1992... 

Fig. 4. Diagram of a cortical cup used by Jasper and Koyama to collect amino acids fronn the cortex surface. The cup is fixed in the skull with dental cement and sealed to the surface of the cortex with silicone gel. The inside diameter of the cup is approximately 1.1 cm, covering a surface of 1 cm (from Jasper and Koyama, 1%9).

The final chapter of this volume deals with the various techniques used to measure amino acid uptake and release both in vitro (slices and synaptosome preparations) and in vivo (cortical cups and push-pull cannulae). 

In low and moderate doses, the methylxanthines—especially caffeine—cause mild cortical arousal with increased alertness and deferral of fatigue. The caffeine contained in beverages—eg, 100 mg in a cup of coffee—is sufficient to cause nervousness and insomnia in sensitive individuals and slight bronchodilation in patients with asthma. The larger doses necessary for more effective bronchodilation commonly cause nervousness and tremor in some patients. Very high doses, from accidental or suicidal overdose, cause medullary stimulation and convulsions and may lead to death. 

The cups are small plastic cylinders that are used to investigate the release of ammo acids from cortical structures m acute and chronic experiments. For acute experiments, Clark and Collins (1976) used a Perspex cup, 4 mm id, that was placed on the surface of the visual cortex. The junction between the brain and cup was sealed with soft white paraffin The cup contained 50 jjlL Ringer solution and was exchanged every 10 mm see Fig. 4) The ion composition of the solution could be changed to study effects on the release The ammo acids in the "exchanged" solution were determined and the temperature in the cup and the electrocorti-cogram of the surface in the cup were monitored. A bipolar platinum electrode was inserted 0.5 mm below the surface of the cortex either within or outside the cup for electrical stimulation During these experiments the animal was anesthetized... 

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