The effects of physostigmine on the electroretinogram in the beagle dog

Abstract

The purpose of the study was to correlate electroretinogram (ERG) parameters with increasing levels of plasma, erythrocyte and ocular tissue cholinesterase inhibition using the beagle dog as a model for human neurovisual toxicity. The anticholinesterase compound physostigmine was administered at various steady-state intravenous infusion rates based on pharmacokinetic estimates of plasma and red blood cell cholinesterase inhibition. The most sensitive parameter was the b-wave amplitude of the rod response, which was significantly depressed compared to pretreatment at all levels of acute cholinesterase depression. The overall maximal ERG response demonstrated a trend of declining a- and b-wave amplitudes, which corresponded with the increased levels of cholinesterase depression, but these differences were not significant. The depression of the electroretinogram rod and cone amplitudes appeared to parallel plasma cholinesterase inhibition more closely than erythrocyte cholinesterase activity. Ocular tissue cholinesterase activity was significantly depressed in the retina (70%), cornea (60%) and dorsal rectus extraocular muscle (46%). Electroretinography may be a useful physiological tool for evaluating the ocular toxicity of certain chemicals or pharmaceuticals associated with cholinesterase biomarker activity.

Electroretinography recordings using a light emitting diode active corneal electrode in healthy beagle dogs

“…Components of the ERG change before presentation of ophthalmoscopical abnormalities in the retina [6,24]. Therefore, ERG recording is performed prior to cataract extraction [19] to experimentally evaluate retinal toxicity [10] and diagnose retinal disorders such as generalized progressive retinal atrophy (an inherited form of photoreceptor degeneration) and sudden acquired retinal degeneration associated with sudden visual loss due to acute photoreceptor death in dogs [18,19]. …”

Clinical findings in early onset cone‐rod dystrophy in the Standard Wire‐haired Dachshund

“…This was preferred to other means of stabilizing the eye as it avoided losing important data on follow‐ups, and allowed us to compare new data with data obtained by former examiners using the same anesthetic protocol. Also, several reports in the literature show that different drugs may have a significant impact on the ERG amplitudes and implicit times 29–31 …”

“…Also, several reports in the literature show that different drugs may have a significant impact on the ERG amplitudes and implicit times. [29][30][31] The mode of inheritance of crd in the SWHD is believed to be autosomal recessive. Further studies will be carried out in order to confirm the mode of inheritance and a more detailed discussion on the mode of inheritance will be covered in a separate publication.…”

The Future of Neurotoxicology: A Neuroelectrophysiological Viewpoint

“…Changes in the auditory system have been shown following treatment with jet fuel coupled with noise exposure ( Fechter et al, 2007 ), carbonyl sulfide ( Morgan et al, 2004 ; Sills et al, 2004 ; Herr et al, 2007 ), chlordimeform or developmental glutamate ( Janssen et al, 1983 ; Janssen et al, 1991 ), or polychlorinated biphenyls ( Lilienthal et al, 2011 ; Poon et al, 2011 ). Changes in the ERG have been reported after exposure to methanol ( Eells et al, 1996 ; Eells et al, 2000 ), cholinesterase inhibition ( Jones et al, 1995 ), or lead ( Fox and Rubinstein, 1989 ). Additionally, changes in the central nervous system function of the visual system ( Boyes, 1992 ) have been shown following treatment with trichloroethylene ( Boyes et al, 2005 ), carbon disulfide ( Herr et al, 1992 ), 3,3′-iminodipropionitrile ( Herr et al, 1995 ), and carbaryl or propoxur ( Mwanza et al, 2008 ).…”