Cerebellar cyclic GMP in p,p'-DDT myoclonus: effects of antimyoclonic agents

Area of Science:

• Neuroscience
• Pharmacology
• Toxicology

Background:

• DDT (dichlorodiphenyltrichloroethane) is an insecticide known to cause neurological effects, including myoclonus.
• Cyclic guanosine monophosphate (cGMP) is a key second messenger in the central nervous system, particularly in cerebellar function.
• The precise mechanisms linking DDT-induced myoclonus, cerebellar cGMP levels, and the action of antimyoclonic agents remain unclear.

Purpose of the Study:

• To investigate the relationship between DDT-induced myoclonus and cerebellar cGMP concentrations.
• To determine if antimyoclonic agents counteract DDT-induced elevations in cerebellar cGMP.
• To elucidate the pathways involved in the antimyoclonic effects of these agents on cerebellar cGMP.

Main Methods:

• Mice were administered DDT (600 mg/kg) intragastrically to measure cerebellar cGMP levels.
• The effects of various antimyoclonic agents (L-5HTP plus fluoxetine, clonazepam, phenoxybenzamine, prostaglandin E2, harmaline) on DDT-induced cGMP elevation were assessed.
• The role of the inferior olive-climbing fiber pathway was examined in rats with lesions induced by 3-acetylpyridine.

Main Results:

• DDT administration significantly increased cerebellar cGMP levels approximately fourfold.
• Several antimyoclonic agents successfully counteracted the DDT-induced rise in cerebellar cGMP.
• Cinnanserin, a 5-HT receptor blocker, blocked the antimyoclonic actions but not the cGMP modulation by certain agents.
• Lesioning the inferior olive-climbing fiber pathway did not prevent DDT-induced cGMP elevation, and antimyoclonic agents still affected cGMP levels in these lesioned animals, despite losing their antimyoclonic effect.

Conclusions:

• DDT-induced elevation of cerebellar cGMP is dissociated from DDT-induced myoclonus.
• Antimyoclonic agents counteract DDT-induced cerebellar cGMP increases through mechanisms independent of the olivo-cerebellar tract.