Effect Of Antagonization Of M4 Receptors With Tropicamide, Catalysis And Motor Changes Induced By Nitrergic Inhibition, In Mice

The Parkinson's disease is characterized by the depletion of dopamine, however, there are strong indicators of interactions among other neurotransmitters in the base nuclei, such as in cholinergic neurotransmition. The aim of this study was to evaluate the effect of tropicamide, an M4 receptor antagonist, on the mice’s motor behavior induced by inhibition of nitric oxide synthase with L-NOARG. 48 male Swiss mice were subdivided into 6 experimental groups. Each animal was subjected to stereotaxic surgery for implantation of cannulae, in the striatum. After 7 days, each animal received an intraperitoneal injection of saline or L-NOARG and then received intracerebral injection of saline or tropicamide at doses of 25 or50 nM. The animals were subjected to the bar catalepsy test and the Open Field test. p<0.05Tropicamide, both doses (was able to completely reverse the catalepsy of these animals at moments 5, 35 and 65 minutes after the application of the drugs (p<0.05). L-NOARG (L NOARG + saline) led to significant changes in the horizontal and vertical exploitation behavior in the animals (Tukey post-test, p< 0.05). These motor alterations were reversed by tropicamide (50 nM). In conclusion, L-NOARG significantly altered the animals’ motor behavior, and these changes were reversed with tropicamide.