Shaw PJ; Charles SL; Salt TE; (1999) Actions of 8-Bromo-cyclic-GMP on neurones in the rat thalamus in vivo and in vitro. Brain Research, 833: 272-277
The diffusible intercellular messenger nitric oxide may have a modulatory role in the thalamus and this
action may be mediated via activation of soluble guanylate cyclase. In order to investigate this possibility,
we applied the cyclic-GMP analogue 8-Bromo-cyclic-GMP (8-Br-cGMP) onto neurones in the
ventrobasal and lateral geniculate nuclei of the thalamus in anaesthetised rats, and compared its effects
with those of a nitric oxide donor. 8-Br-cGMP enhanced the responses of neurones to iontophoretically
applied NMDA and AMPA . Furthermore, somatosensory and visual responses of ventrobasal and
lateral geniculate neurones were enhanced to 274±76 % and 217±69 % of control values, respectively.
These effects were similar to those seen with nitric oxide donors in this study and previous work from this
laboratory. When applied to thalamic neurones in an in vitro slice preparation, 8-Br-cGMP caused a
membrane depolarisation associated with a decrease in input resistance. These findings indicate that
activation of guanylate cyclase can cause a membrane depolarisation of thalamic neurones in vitro, and
that this effect is sufficient to enhance action responses to ionotropic glutamate receptor stimulation via
either exogenous agonists or sensory stimulation.
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