Journal of Neuroscience, Vol 6, 3250-3257, Copyright © 1986 by Society for Neuroscience
The role of spinal cord cyclic AMP in the acoustic startle response in rats
JH Kehne, DI Astrachan, E Astrachan, JF Tallman and M Davis
Drugs thought to increase intracellular levels of cAMP were infused
intrathecally into the subarachnoid space of the lumbar spinal cord, and
the effects on the acoustic startle response in rats were measured.
Intrathecal infusions of the cAMP analogs dibutyryl cAMP or 8-bromo cAMP
(12.5-100 micrograms) produced marked, dose-dependent increases in startle
amplitude compared to the infusion of artificial cerebrospinal fluid (CSF).
Local infusions of dibutyryl cAMP at more rostral levels of the spinal cord
or brain failed to mimic the excitatory effect seen following lumbar
intrathecal infusion. No excitation of startle was seen following
intrathecal infusion of cAMP itself, ATP, 5'-AMP, or dibutyryl cGMP. A weak
excitation of startle was seen following intrathecal, but not
intraventricular, infusion of the water-soluble adenylate cyclase activator
forskolin 7-deacetyl-7-O-hemisuccinic acid (forskolin-DHA; 5.0-100
micrograms, in artificial CSF), whereas forskolin itself [0.01-200
micrograms, in dimethyl sulfoxide (DMSO)] was without consistent effect.
Finally, intrathecal infusion of the selective phosphodiesterase inhibitor
Rolipram (12.5-200 micrograms) produced a marked excitation of startle
similar in magnitude to the effects produced by cAMP analogs. The
excitatory effects of intrathecally infused dibutyryl cAMP, 8-bromo cAMP,
forskolin-DHA, or Rolipram support a functional link between spinal cord
cAMP and the acoustic startle reflex. Possible sites of cAMP action on
startle are discussed.