![]() Sep 27, 2016. Because of the hypothalamus's functions, the limbic system is directly in control of your “stress response” and these key functions: Heart rate; Blood. Too much activation of one causes high amounts of anxiety, but too much of the other causes low motivation and symptoms like fatigue. Here are ways to. For example, the amygdala (AM), a key limbic structure, is involved in tagging neutral stimuli with emotional content (LeDoux, 1995; Rolls, 1999), thereby creating chains of associations based on emotional experiences. Connections from the AM to lower (hypothalamic and brainstem) structures activate emotional response. The local anesthetic procaine, when administered to humans intravenously (i.v.), yields brief intense emotional and sensory experiences, and concomitant increases in anterior paralimbic cerebral blood flow, as measured by positron emission tomography (PET). Procaine's high muscarinic affinity, together with the distribution of muscarinic receptors that overlaps with brain regions activated by procaine, suggests a muscarinic contribution to procaine's emotional and sensory effects. This study evaluates the effects of procaine on cerebral muscarinic cholinergic receptors in the anesthetized rhesus monkey. ![]() ![]() ![]() Whole brain and regional muscarinic receptor binding was measured before and after procaine administration on the same day in three anesthetized rhesus monkeys with PET and the radiotracer 3-(3-(3[ 18F]fluoropropylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine ([ 18F]FP-TZTP), a cholinergic ligand that has preferential binding to muscarinic (M 2) receptors. On separate days each animal received six different doses of i.v. Procaine in a randomized fashion. Procaine blocked up to ∼90% of [ 18F]FP-TZTP specific binding globally in a dose-related manner. There were no regional differences in procaine's inhibitory concentration for 50% blockade (IC 50) for [ 18F]FP-TZTP. Tracer delivery, which was highly correlated to cerebral blood flow in previous monkey studies, was significantly increased at all doses of procaine with the greatest increases occurring near procaine's IC 50 for average cortex. Furthermore, anterior limbic regions showed greater increases in tracer delivery than nonlimbic regions. Procaine has high affinity to muscarinic M 2 receptors in vivo in the rhesus monkey. This, as well as a preferential increase of tracer delivery to paralimbic regions, suggests that action at these receptors could contribute to i.v. Procaine's emotional and sensory effects in man. These findings are consistent with other evidence of cholinergic modulation of mood and emotion. The local anesthetic procaine has unique neuropsychopharmacological properties that make it useful as a discrete probe of the limbic system and associated studies of emotion. In this regard, it has been used as an affective challenge in healthy volunteers (; ), and patients with mood disorders () and panic disorder (), as well as in individuals abusing alcohol () and cocaine (). Procaine (1.84 mg/kg), when administered intravenously (i.v.) in healthy volunteers (), results in brief intense emotional (ranging from euphoria to dysphoria) and sensory experiences (visual, auditory, and olfactory illusions/hallucinations) in association with increased relative anterior paralimbic cerebral blood flow (CBF) as measured with [ 15O] water positron emission tomography (PET) (). ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. Archives
April 2018
Categories |