Journal of Neuroscience, Vol 5, 2618-2625, Copyright © 1985 by Society for Neuroscience
Decreased cerebellar 3',5'-cyclic guanosine monophosphate levels and insensitivity to harmaline in the genetically dystonic rat (dt)
JF Lorden, GA Oltmans, TW McKeon, J Lutes and M Beales
The dystonic rat (dt) is an autosomal recessive mutant displaying a complex
motor syndrome that includes sustained axial twisting movements. The
syndrome is correlated with increased glutamic acid decarboxylase activity
in the deep cerebellar nuclei and increased cerebellar norepinephrine
levels in comparison with phenotypically normal littermates. Biochemical,
behavioral, and anatomical techniques were used to investigate the
possibility that the abnormalities noted in the cerebellum of the dt rat
were indicative of altered function of the major projection neurons of the
cerebellar cortex, the Purkinje cells. Phenotypically normal rats showed
tremor in response to harmaline, a drug that acts on the inferior olive to
produce bursting in the climbing fiber pathway. Dystonic rats were
insensitive to the effects of harmaline but did respond to oxotremorine.
Levels of the cyclic nucleotide 3',5'-cyclic guanosine monophosphate, a
biochemical marker for Purkinje cells, increased in response to harmaline
in normal rats but were significantly lower in dystonic rats under both
basal and harmaline-stimulated conditions. Purkinje cell soma size was
reduced in the dystonic rats but no other morphological correlates of the
behavioral or biochemical deficits were noted. Taken together with other
observations on this mutant, the results suggest an impairment in the
cerebellum or in its connections with lower brainstem and spinal cord
sites.