RESUMEN
Significant improvements in time-correlated single photon counting (TCSPC) Raman spectroscopy acquisition times can be achieved through exploitation of megahertz (MHz) laser repetition rates. We have developed a TCSPC Raman spectroscopy system based on a high peak power (>40W) pulsed laser, a high pulse repetition rate (40 MHz), a custom f/1.5 spectrometer, and a 512 spectral channel × 16 time bin single photon avalanche diode line sensor. We report millisecond Raman spectrum acquisition times, a peak Raman count rate of 104 kcps, and a linewidth aggregated count rate of 440 kcps with a diamond sample. This represents a three-order-of-magnitude increase in measured Raman count rate in comparison with a 104 kHz pulsed laser operating at 300 W and a four-order-of-magnitude increase over a 0.1 W pulsed laser operating at 40 MHz. A Raman-to-fluorescence ratio of 4.76 is achieved with a sesame oil sample at a 20 MHz repetition rate. Achieving high count rates and Raman-to-fluorescence ratios unlocks the potential of combined Raman/fluorescence lifetime spectroscopy for imaging and other short acquisition time applications.
RESUMEN
Clinical evidence suggests that prenatal exposure to cannabis may be conducive to long-term neurobehavioral impairments in executive and attentional domains. Such sensorimotor alterations might be related to disorders in gating functions. Hence, the present study was undertaken to assess the effects of long-term prenatal exposure to WIN 55,212-2, a potent cannabinoid receptor agonist, on prepulse inhibition of the acoustic startle reflex, a well-validated paradigm to test sensorimotor gating. In utero exposure to WIN 55,212-2 (0.5, 1 mg/kg, from day 5 to 20 of gestation) failed to alter startle magnitude in rats in comparison with controls. Similarly, prepulse inhibition of the startle was not significantly affected by such treatment, regardless of the age when behavioral testing was carried out (40, 60 or 80 days). Interestingly, prenatal treatment with WIN 55,212-2 (0.5 mg/kg, from day 5 to 20 of gestation) induced no differences in the prepulse inhibition-disrupting effects of apomorphine (0.125, 0.25 mg/kg, s.c.) and dizocilpine (0.05, 0.1 mg/kg, s.c.), suggesting that a prenatal exposure to a cannabinoid receptor agonist is likely unable to affect sensitivity of sensorimotor gating substrates to dopaminergic agonists and NMDA receptor antagonists. Our results show that prenatal exposure to cannabis does not affect reflex reactivity to environmental stimuli, ruling out that the observed impairments in executive functions are to refer to sensorimotor gating alterations.