Methylphenidate and Ethanol Interactions in the Visual Cortex and Superior Colliculus: Flash Evoked Potentials, Body Temperature, and Behavior

Methylphenidate (MPD) is a psychostimulant used to treat Attention Deficit Hyperactivity Disorder (ADHD). Most adult ADHD patients use ethanol while under the influence of prescribed MPD. In two studies, this research examined the separate and combined effects of ethanol and MPD on flash-evoked potentials (FEPs) recorded from the visual cortex (VC) and superior colliculus (SC) of chronically implanted male Long-Evans rats, as well as on body temperature and open field behavior. In the first study, on separate days, either saline or ethanol (2.0 g/kg, ip) was given 5 min prior to either saline or MPD (2.9 mg/kg, ip). FEPs were recorded 10 and 20 min after the second injection. In the VC, ethanol decreased the amplitudes of several components, but increased P47. In contrast, MPD increased the amplitudes of N31, P47, and N140, but decreased amplitude for components P23, P87, and P230. Ethanol also increased the latency of several components. In the SC, ethanol decreased the amplitude of all three components, while MPD increased the amplitude of component P39. Ethanol also increased the latency of all three components. During FEP testing, ethanol decreased body movement while MPD increased movement. In subsequent open field observations, line crossings were significantly increased but rearings were significantly decreased by ethanol. Both ethanol and MPD produced significant hypothermia. The second study was conducted with the same procedure, except the MPD dose was 11.6 mg/kg, ip. Results from this study showed that in the VC, ethanol decreased the amplitudes of several components, but increased P54. MPD increased the amplitudes of P54 and N130, and counteracted the depressant effect of ethanol on component P54, but decreased amplitude for 4 components. Both ethanol and MPD increased the latency of several components. In the SC, ethanol decreased the amplitude of all three components, while MPD increased the amplitude of component P38 but decreased N51. Ethanol also increased the latency of all three components, while MPD increased the latency for components P38 and N51. During FEP testing, ethanol decreased body movement while MPD increased movement. In open field observations, line crossings were significantly increased by MPD. Rearings were eliminated by ethanol but increased by MPD. With the combination treatment, MPD counteracted the effects of ethanol on rearings. Both ethanol and MPD produced significant hypothermia