Measurement of some small-molecule and peptide neurotransmitters in-vitro using a fiber-optic probe with pulsed ultraviolet resonance Raman spectroscopy.

Many techniques have been developed to investigate the chemistry associated with brain activity. These techniques generally fall into two categories: fast techniques with species-limited sensitivity; and generally slower techniques with broader species sensitivity. Therefore, a need exists for a fast, minimally invasive technique that is sensitive to a wide array of biologically relevant compounds in order to measure chemical brain events in real time. The work presented here describes the development of a novel spectroscopic neurotransmitter probe for the rapid and simultaneous detection of a variety of neurotransmitters. A fiber-optic-linked Raman and tunable ultraviolet resonance Raman system was assembled with custom designed optical fiber probes. Using this system, the ultraviolet resonance Raman spectra of some small-molecule and peptide neurotransmitters were measured in-vitro with a fiber-optic probe and are reported here for the first time. The probe has furthermore been used to measure neurotransmitter secretions obtained from depolarized rat pheochromocytoma (PC12) cells. These results demonstrate the general utility of this approach which, due to the fiber-optic implementation, could potentially also be applied to in-vivo neurotransmitter determinations.