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Alteration of GABAergic neurotransmission by pulsed infrared laser stimulation.

ABSTRACT: Transient electrical impulses are conventionally used to elicit physiological responses in excitable tissues. While electrical stimulation has many advantages, it requires an electrode-tissue interface, exhibits relatively low spatial selectivity and always produces a "stimulus artifact". Recently, it has been shown that pulsed, low-energy infrared laser light can evoke nerve, muscle and sensory responses similar to those induced by traditional electrical stimulation in a contact-free, damage-free, artifact-free and spatially selective manner. However, the effect of transient infrared laser light on neurotransmission in the CNS is still largely unknown. Here, we tested the effect of infrared laser light on GABAergic neurotransmission. We recorded spontaneous inhibitory postsynaptic currents (sIPSCs) from cultured rat cortical neurons prior to and after infrared laser stimulation. Using transient infrared laser light, we either stimulated the neuronal soma that had axonal projections to the recorded neuron or directly stimulated the axons that projected to the recorded neuron. Optical stimulation led to enhanced amplitude, decreased decay time constant and increased frequency of sIPSCs. These alterations of sIPSC properties produced by optical stimulation were specifically mediated by GABA(A) receptors and caused by the transient laser light per se since no exogenous substances such as caged compounds were used. These data show that optical stimulation using transient infrared laser light can alter GABAergic neurotransmission and demonstrate that it may be an alternative approach to electrical stimulation in studying GABAergic function.

SUBMITTER: Feng HJ

PROVIDER: S-EPMC3096872 | biostudies-literature | 2010 Sep

REPOSITORIES: biostudies-literature

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Alteration of GABAergic neurotransmission by pulsed infrared laser stimulation.

Feng Hua-Jun HJ Kao Chris C Gallagher Martin J MJ Jansen E Duco ED Mahadevan-Jansen Anita A Konrad Peter E PE Macdonald Robert L RL

Journal of neuroscience methods 20100721 1

Transient electrical impulses are conventionally used to elicit physiological responses in excitable tissues. While electrical stimulation has many advantages, it requires an electrode-tissue interface, exhibits relatively low spatial selectivity and always produces a "stimulus artifact". Recently, it has been shown that pulsed, low-energy infrared laser light can evoke nerve, muscle and sensory responses similar to those induced by traditional electrical stimulation in a contact-free, damage-fr ...[more]

PMID: 20654645

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Project description:A variety of stimuli activating vestibular end organs, including sinusoidal galvanic vestibular stimulation, whole body rotation and tilt, and head flexion have been shown to evoke significant changes in blood pressure (BP) and heart rate (HR). While a role for the vertical semicircular canals in altering autonomic activity has been hypothesized, studies to-date attribute the evoked BP and HR responses to the otolith organs. The present study determined whether unilateral activation of the posterior (PC) or anterior (AC) semicircular canal is sufficient to elicit changes in BP and/or HR. The study employed frequency-modulated pulsed infrared radiation (IR: 1,863 nm) directed via optical fibers to PC or AC of adult male Long-Evans rats. BP and HR changes were detected using a small-animal single pressure telemetry device implanted in the femoral artery. Eye movements evoked during IR of the vestibular endorgans were used to confirm the stimulation site. We found that sinusoidal IR delivered to either PC or AC elicited a rapid decrease in BP and HR followed by a stimulation frequency-matched modulation. The magnitude of the initial decrements in HR and BP did not correlate with the energy of the suprathreshold stimulus. This response pattern was consistent across multiple trials within an experimental session, replicable, and in most animals showed no evidence of habituation or an additive effect. Frequency modulated electrical current delivered to the PC and IR stimulation of the AC, caused decrements in HR and BP that resembled those evoked by IR of the PC. Frequency domain heart rate variability assessment revealed that, in most subjects, IR stimulation increased the low frequency (LF) component and decreased the high frequency (HF) component, resulting in an increase in the LF/HF ratio. This ratio estimates the relative contributions of sympathetic nervous system (SNS) and parasympathetic nervous system (PNS) activities. An injection of atropine, a muscarinic cholinergic receptor antagonist, diminished the IR evoked changes in HR, while the non-selective beta blocker propranolol eliminated changes in both HR and BP. This study provides direct evidence that activation of a single vertical semicircular canal is sufficient to activate and modulate central pathways that control HR and BP.

Dataset Information

Alteration of GABAergic neurotransmission by pulsed infrared laser stimulation.

Publications

Alteration of GABAergic neurotransmission by pulsed infrared laser stimulation.

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