Animal studies electrophysiological effects

An intermediate-duration oral MRL of 0.0007 mg/kg/day was derived for methyl parathion based on the observation of electrophysiological effects in the central and peripheral nervous systems of male rats exposed to methyl parathion through gavage administration of 0.22 mg/kg/day to the dams on days 5-15 of gestation and days 2-28 of lactation, followed by direct administration of the same dose to the male pups for 8 weeks. More marked effects occurred at the two higher doses, 0.44 and 0.88 mg/kg/day. The effects were dose-related, and were statistically significant at all three dose levels. The MRL was derived by dividing the LOAEL from this study (0.22 mg/kg/day) by an uncertainty factor of 300 (3 for a minimal LOAEL, 10 for extrapolation from animals to humans, and 10 for human variability). 

Electrophysiological effects Extracts of hypericum were examined for their electrophysiological effects in animals. The onset of effects occurred 3-4 hours after administration. Frequencies affected first were in the alpha range and were maximal in the frontal cortex (Dimpfel and Hofmann 1995). Another study examined the EEG effects for two hypericum extracts in rats one extract high in hyperforin and lacking naphthodi-anthrones (C02), and another extract (LI 160) low in hyperforin. Both extracts showed similar early alpha effects, but only LI 160 had a late effect of increased delta frequencies. The alpha effects are comparable to... 

A large number of functional and electrophysiologic studies in transected animals support the conclusion that hallucinogens facilitate spinal MSRs and PSRs in both flexor and extensor muscles. Furthermore, these studies show that 5-HT antagonists effectively block the observed excitatory behavioral effects, suggesting mediation by spinal excitatory 5-HT receptors. 

The assumption that the effects on brain reward mechanisms in animals produced by acute administration of addictive drugs (the brain reward enhancement measured electrophysiologically and the DA enhancement measured neurochemically in Acb) has relevance to self-reported euphoria at the human level is supported by real-time, in-vivo, positron emission tomography studies of DA transporter occupancy in human brain loci following acute cocaine administration (Volkow et al. 

Electroconvulsive therapy has been used as antidepressive, mood-stabilizing and antipsychotic treatments (Eitan and Lerer 2006 Shapira et al., 1991). It is reported that electroconvulsive shocks (ECS), an animal model for the ECT, affect the NE system. Thus, both acute and chronic ECS increase cortical and hippocampal NE release. Chronic ECS also desensitize a2-adrenergic autoreceptors in the PFC (Thomas et al., 1992). Paradoxically, electrophysiological studies report that chronic ECS suppress the firing activity of NE neurons in the ECS (Grant and Weiss 2001). Based on the evidences of ECS-induced increase in brain NE levels, it can be concluded that the benefitial effect of the ECT is mediated, at least in part, via NE system. 

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