Extracellular adenosine, AMP, cyclic AMP and ammonia: Sampling and analysis techniques.

摘要

Ammonia, adenosine 3′:5′-cyclic monophosphate (CAMP) and adenosine have been implicated as neuromodulators. Neither their roles nor their sources have been completely defined. This thesis describes experiments that examine the source of extracellular ammonia, explore methods of quantitating extracellular cAMP and study the source and role of extracellular adenosine.; First, ammonia is not found to be present as a counterion to glutamate within hippocampal synaptic vesicles. Next, a molecular intracellular cAMP probe is determined to be inappropriate for use as a sensor for measurements of urinary cAMP. Finally, an extracellular metabolic source of adenosine is hypothesized.; Adenosine has previously been shown to produce analgesia via A, receptors. Behavioral experiments, outlined here, demonstrate that adenosine 5 ′-monophosphate (AMP) produces antinociception in an intraplantar capsaicin model of secondary hyperalgesia. The action of AMP is shown to be specific to A₁ receptors, implicating the intermediate conversion of AMP to adenosine. These results suggest that there is a metabolic source of adenosine that is involved in antinociception.; A novel, linear transverse push-pull micro-probe is designed to overcome the limitations of microdialysis. The recovery of the probe is characterized in terms of flow rate, gap distance and the ability to assay enzymatic activity. The micro-probe is used to sample the extracellular environment of the rat dorsal spinal cord.; Low adenosine concentrations are detected in the extracellular space of the spinal cord dorsal horn. High ecto 5′-nucleotidase activity is assayed by the production of adenosine in this region using the micro-probe. These results suggest that AMP plays a role in the generation of the antinociceptive, neuromodulator adenosine.; Together these experiments illustrate the close association of chemistry and neuroscience. The tools of analytical chemistry can be utilized to investigate questions in the field of neuroscience and phenomena of the neurosciences can lead to the development of novel analytical chemical techniques.