PubMed · 4872497
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O Gisvold, H V Maulding. 1968. Basically substituted dioxolanes and dioxanes.. https://doi.org/10.1002/jps.2600570512
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gamma-Hydroxybutyric acid (GHB), a naturally occurring analog of GABA, induces absence-like seizures in rats. We characterized the interaction of 3alpha-hydroxy steroids, alphaxalone and tetrahydrodeoxycorticosterone (which are potent modulators of GABAA receptors) with GHB binding sites in rat brain cortical membranes. The steroids inhibited [3H]GHB binding in a dose-dependent fashion (IC50 approximately 1 microM). Neither bicuculline nor GABA altered the dose-response of steroids in the [3H]GHB assay, suggesting that there was no GABAA component involved in the steroid-inhibition of [3H]GHB binding. Also, non 3alpha-hydroxy steroids were inactive in displacing [3H]GHB. Because GHB-induced absence seizures evolve most readily from layers I-IV of frontoparietal cortex and thalamic relay nuclei, we determined if the interaction of steroids with GHB binding sites in layers I-IV of frontoparietal cortex and thalamic relay nuclei was altered during GHB-induced absence seizures. We found that during GHB-seizures steroid-inhibition of [3H]GHB binding was increased selectively in thalamic relay nuclei but not in the layers I-IV of frontoparietal cortex or any other brain regions tested. This increase in steroid-inhibition of [3H]GHB binding in thalamus was apparent about 30 min after the onset of seizures, but not at the seizure-onset. As the seizures dissipated, the IC50 values for steroids rose to the pre-seizure level. These data suggest that the enhancement in steroid-inhibition of [3H]GHB binding in thalamic relay nuclei observed during GHB-seizures was caused by absence seizures.
Studies of drug distribution to brain should be controlled for the experimental method used. Numerous methods have been employed to ascertain brain distribution and many of these approaches use anesthetic agents. The in situ rat brain perfusion method is one of the most sensitive and widely used methods for evaluating brain distribution profiles. There has been no evaluation of the effects of anesthetic agents on parameters associated with this method (i.e. cerebral perfusion fluid flow, brain vascular volume and blood-brain barrier permeability). We evaluated the effects of the anesthetic agents pentobarbital and ketamine combinations on these baseline parameters. The results suggest that the anesthetic agent has no effect on these parameters and anesthetic selection is open to the choice of the investigator when using the perfusion method.
To investigate the possible mechanisms by which neurons in the caudate-putamen (CPu) and globus pallidus (GP) participate in pain and nociception, the present study characterized the response properties of CPu and GP neurons to non-noxious and noxious thermal stimuli in anesthetized rats. Nociceptive CPu and GP neurons were capable of encoding noxious thermal stimuli and 79% of these thermally responsive neurons also responded to noxious mechanical stimuli. Thermally responsive neurons were activated during the phasic rise and fall of the thermal shift in addition to the plateau temperature. The ability of CPu and GP neurons to encode noxious thermal stimulation intensity and respond during the dynamic phase of the stimulus suggests that these neurons may contribute to the behavioral response to minimize bodily harm.