Acute effects of estrogen upon methamphetamine induced neurotoxicity of the nigrostriatal dopaminergic system.
3; 4-Dihydroxyphenylacetic Acid/metabolism; Animals; Dopamine/metabolism; Drug Interactions; Estrogens/metabolism/*pharmacology; Female; Methamphetamine/antagonists & inhibitors/*toxicity; Mice; Neostriatum/*drug effects/metabolism/physiopathology; Neural Pathways/*drug effects/metabolism/physiopathology; Neuroprotective Agents/metabolism/pharmacology; Neurotoxins/antagonists & inhibitors/toxicity; Ovariectomy; Parkinson Disease/drug therapy/metabolism/physiopathology; Presynaptic Terminals/drug effects/metabolism; Reaction Time/drug effects/physiology; Sex Factors; Substantia Nigra/*drug effects/metabolism/physiopathology
Estrogen acts as a neuroprotectant of the nigrostriatal dopaminergic system when given chronically to female mice prior to Methamphetamine (MA) insult. In this report, we tested the acute effects of Estradiol Benzoate (EB-10 microg in Oil) in ovariectomized CD-1 mice to function as a neuroprotectant when administered prior to (Experiment 1) or after (Experiment 2) MA treatment. Striatal dopamine (DA) concentrations and DOPAC/DA ratios were measured to assess the neuroprotective effects of EB. In Experiment 1, we observed that EB exerted a neuroprotective effect upon striatal dopamine concentrations when administered at 24 and 12, but not at 0.5, hours prior to MA injection and upon DOPAC/DA ratios when administered at 24, 12 and 0.5 hours prior to MA. In Experiment 2, no evidence for estrogen to protect the striatum from MA insult was obtained when EB was administered at 15, 30, 60 or 120 minutes after MA. These results show that EB can act as a modulator of MA-induced nigrostriatal dopaminergic neurotoxicity suggestive of a neuroprotectant, when administered within 0.5 hour of MA insult as assessed by measures of DOPAC/DA, but fails to prevent depletion of DA when given after MA insult. The data suggest that estrogen may exert this rapid neuroprotective effect through a non-genomic mechanism.
Gajjar T M; Anderson L I; Dluzen D E
Journal of neural transmission (Vienna, Austria : 1996)
2003
2003-11
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
<a href="http://doi.org/10.1007/s00702-003-0045-3" target="_blank" rel="noreferrer noopener">10.1007/s00702-003-0045-3</a>
High concentrations of divalent cations isolate monosynaptic inputs from local circuits in the auditory midbrain.
inferior colliculus; Animals; Mice; Acoustic Stimulation; Neural Inhibition/drug effects/*physiology; high divalents; local circuits; monosynaptic; first spike latency; Inferior Colliculi/drug effects/*physiology; Reaction Time/drug effects/physiology; Synapses/drug effects/*physiology; Cations; Divalent/*pharmacology
Hierarchical processing of sensory information occurs at multiple levels between the peripheral and central pathway. Different extents of convergence and divergence in top down and bottom up projections makes it difficult to separate the various components activated by a sensory input. In particular, hierarchical processing at sub-cortical levels is little understood. Here we have developed a method to isolate extrinsic inputs to the inferior colliculus (IC), a nucleus in the midbrain region of the auditory system, with extensive ascending and descending convergence. By applying a high concentration of divalent cations (HiDi) locally within the IC, we isolate a HiDi-sensitive from a HiDi-insensitive component of responses evoked by afferent input in brain slices and in vivo during a sound stimulus. Our results suggest that the HiDi-sensitive component is a monosynaptic input to the IC, while the HiDi-insensitive component is a local polysynaptic circuit. Monosynaptic inputs have short latencies, rapid rise times, and underlie first spike latencies. Local inputs have variable delays and evoke long-lasting excitation. In vivo, local circuits have variable onset times and temporal profiles. Our results suggest that high concentrations of divalent cations should prove to be a widely useful method of isolating extrinsic monosynaptic inputs from local circuits in vivo.
Sivaramakrishnan Shobhana; Sanchez Jason Tait; Grimsley Calum Alex
Frontiers in neural circuits
2013
1905-07
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
<a href="http://doi.org/10.3389/fncir.2013.00175" target="_blank" rel="noreferrer noopener">10.3389/fncir.2013.00175</a>