Anterior thalamic nucleus stimulation: issues in study design
Hans O Lüders in Deep Brain Stimulation and Epilepsy, 2020
Mirski et al.16 demonstrated that high frequency stimulation of the mammillary bodies significantly increased the PTZ dose needed to produce clonic and tonic seizures compared to control animals or animals in which the stimulating electrode missed the hypothalamus (Figure 25.2). High frequency (100 Hz) stimulation behaved as an inhibitory stimulus, to judge by comparison with injection of the GABA agonist, muscimol, into mammillary bodies. Both high frequency stimulation and muscimol inhibited the time to clonic seizures and prolonged the duration of the EEG discharge prior to onset of the behavioral seizure. The posterior hypothalamus is a relatively difficult clinical stereotactic target, deep in the brain and near important basal vessels. Hemorrhage in the mammillary bodies might precipitate Wernicke’s encephalopathy. However, the mammillothalamic tracts link the mammillary bodies to the more accessible anterior thalamus. This connection is part of the so-called limbic circuit of Papez: hippocampus → fornix → mammillary bodies → anterior thalamus → cingulate → cingulum bundle → entorhinal cortex, then back to hippocampus.
Synthesis, Enzyme Localization, and Regulation of Neurosteroids
Sheryl S. Smith in Neurosteroid Effects in the Central Nervous System, 2003
Recently we have extended the analysis of estradiol modulation of GABA-mediated calcium influx to cultured hippocampal neurons. A similar preparation to that used for hypothalamic neurons was employed with the exception that neurons were cultured at a later stage of development, beginning on embryonic day 18 and imaged on what would be considered the developmental equivalent of the day of birth. Muscimol exerted a depolarizing effect in the majority of hippocampal neurons imaged at this age, as evidenced by calcium influx. The source of the increased intracellular free calcium was again confirmed to be via the L-type calcium channel, and the magnitude of the calcium transient was again increased by pretreatment of cultured neurons with estradiol. Representative traces and color-enhanced images of calcium influx into cultured hippocampal neurons are presented in Figure 8.4. The ability of estradiol to enhance calcium influx in hippocampal neurons depolarized by GABA could be the causal variable in sex differences in hippocampal damage following excitatory GABA, as well as the increased cell death observed after estradiol pretreatment in vivo and in vitro.
The Circuitry Mediating the Translation of Motivational Stimuli Into Adaptive Motor Responses
Peter W. Kalivas, Charles D. Barnes in Limbic Motor Circuits and Neuropsychiatry, 2019
Compared to the VTA and nucleus accumbens, the pharmacology of the VP is less well characterized. Table 1 reveals that motor activity can be elicited pharmacologically from the VP by the stimulation of mu opioid,91,92 DA,24 EAA73 and tachykinin receptors (unpublished personal observation) or inhibition of GABAA receptors.92 The stimulation of GABAA receptors produces a biphasic effect with respect to dose. Thus, at low doses muscimol inhibits motor activity elicited pharmacologically from the nucleus accumbens while at higher doses it increases locomotion.91,92 The microinjection of neurotensin into the VP was found to partly inhibit motor activity elicited by the administration of opioids or DA into the nucleus accumbens.76
Toxicity of muscimol and ibotenic acid containing mushrooms reported to a regional poison control center from 2002–2016
Published in Clinical Toxicology, 2019
Michael J. Moss, Robert G. Hendrickson
There are several Amanita mushroom species throughout the world which contain ibotenic acid and muscimol including Amanita. Muscaria (AM), A. pantherina (AP), A. gemmata, A. aprica, and A. regalis [1–3]. AM has been used by various cultures for religious activities, supporting work and physical exercise, and medicinal purposes [4]. Modern usage is generally for recreational and psychoactive effects [5]. Ibotenic acid and muscimol are isoxazole derivatives that resemble the neurotransmitters glutamate and GABA, respectively [6]. Thus, ibotenic acid may induce excitatory effects while muscimol causes sedative effects. There are numerous other chemical constituents in these species of mushrooms that have unknown effects. Muscarine, once thought to be the primary toxin in AM, has been shown to be present only in miniscule quantities [7].
The White Panther – Rare exposure to Amanita multisquamosa causing clinically significant toxicity
Published in Clinical Toxicology, 2021
V. Vohra, I. V. Hull, K. T. Hodge
Scant literature exists surrounding Amanita multisquamosa exposures. Toxicity has been compared to Amanita muscaria ingestion, with primarily neurological features and mild gastrointestinal (GI) effects [2,3]. Previous cases include a Canadian family who experienced GI symptoms and demonstrated erratic behavior three hours after eating cooked specimens, resembling Amanita muscaria toxicosis [3]. High concentrations of ibotenic acid and muscimol have been found in Amanita multisquamosa samples, supporting comparisons to Amanita muscaria [4]. Ibotenic acid exerts excitatory central nervous system (CNS) effects while muscimol produces CNS depression [5]. Symptoms may appear within 30–120 min and can last 10–24 h [4,5]. Symptomatic and supportive care is indicated [5]. Our patient had a cardiac conduction abnormality of unknown etiology. Comprehensive molecular characterization of other toxins in Amanita multisquamosa has not been elucidated, therefore this exposure cannot be ruled out as a potential cause.
Suckling induced activation pattern in the brain of rat pups
Published in Nutritional Neuroscience, 2018
János Barna, Eva Renner, Antónia Arszovszki, Melinda Cservenák, Zsolt Kovács, Miklós Palkovits, Arpád Dobolyi
The Ins is known to receive gustatory input, but sensory perception of food-related stimuli including seeing and smelling and its association with the rewarding/hedonic aspects of food items also elicits its increased activation.28–30 In addition, the Ins integrates perception, emotion, interoceptive awareness, and cognition and may participate in the decision-making processes regarding eating behavior in humans.31,32 Thus, muscimol-mediated inactivation of the Ins diminishes intake, total feeding duration, and average feeding bout duration.33 Since a portion of insular cortical neurons were activated in response to suckling, it is conceivable that the Ins plays similar roles in suckling pups, as well.
Related Knowledge Centers
- Amanita Muscaria
- Depressant
- Gabaa Receptor
- Hallucinogen
- Ibotenic Acid
- Psychoactive Drug
- Agonist
- Sedative
- Isoxazole
- Opioid