Huntington's disease / edited by Thomas N. Chase, Nancy S. Wexler, André Barbeau.
- Date:
- 1979
Licence: Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)
Credit: Huntington's disease / edited by Thomas N. Chase, Nancy S. Wexler, André Barbeau. Source: Wellcome Collection.
764/856 page 732
![732 EFFECTS OF GABA-MIMETICS s. N. pars compacta MUSC « í ч 50i О- Т Т Т Т Т Т У т 5 min п S. N. pars reticulata MUSC I 100-] O-l I^ÉÉl'IMMÊKléÊi^iKMiâàiMâàâiiàÊàÊiillÊllii N О MUSC I т т т т т т PIC I lOOl ijJi 5 min FIG. 2. Effects of systemic muscimol upon the firing rates of rat nigral neurons. Top trace: Effects of increasing doses of muscimol on the firing rate of a substantia nigra pars compacta neuron. Successive doses were injected l.v. at 2-min intervals in increasing increments so that each dose doubled the previously administered cumulative dose (i.e., 0.05, .0.05, 0.1, 0.2, 0.4, 0.8, 1.6, 3.2, and 6.4 mg/kg; total administered dose, 12.8 mg/kg). Middle trace: Effect of a single i.v. dose of 1.6 mg/kg muscimol on the firing rate of a substantia nigra pars reticulata neuron. Bottom trace: Effect of cumulative (see above) i.v. doses of muscimol on the firing rate of a pars reticulata neuron. This cell was completely inhibited by a cumulative dose of 3.2 mg/kg. The inhibition was reversed by the subsequent i.v. administration of Picro¬ toxin, 4.5 mg/kg. Evidence Suggesting Actions of Muscimol on Pars Reticulata Cells Are Mediated at Central GABA Receptors Several lines of evidence support the assumption that the inhibition of reticu¬ lata cells by intravenous muscimol is due to a direct action of the drug at central GABA receptors. First, the inhibition of reticulata neurons was reversible by subsequent intravenous administration of GABA antagonists. Both picrotoxin (Fig. 2) and bicuculline hydrochloride (0.8 /xmoles/kg; not shown) were able to restore firing of cells after complete muscimol-induced inhibition. However,](https://iiif.wellcomecollection.org/image/b18021888_0765.JP2/full/800%2C/0/default.jpg)
