Abstract 3,4-Methylenedioxymethamphetamine (MDMA, ecstasy) is a drug of abuse that induces learning and memory deficit. However, there are no experimental data that correlate the behavioral evidence ...with models of synaptic plasticity such as long-term potentiation (LTP) or long-term depression (LTD). Using field potential recordings in rat hippocampal slices of young rats, we found that acute application of MDMA enhances LTP in CA3–CA1 synapses without affecting LTD. Using specific antagonists and paired-pulse facilitation protocols we observed that the MDMA-dependent increase of LTP involves presynaptic 5-HT2 serotonin receptors and postsynaptic D1/D5 dopamine receptors. In addition, the inhibition of PKA suppresses the MDMA-dependent increase in LTP, suggesting that dopamine receptor agonism activates cAMP-dependent intracellular pathways. We propose that MDMA exerts its LTP-altering effect involving a polysynaptic interaction between serotonergic and dopaminergic systems in hippocampal synapses. Our results are compatible with the view that the alterations in hippocampal LTP could be responsible for MDMA-dependent cognitive deficits observed in humans and animals.
•Two week's methylphenidate (MPH) treatment enhanced LTP in the rat PFC in vivo.•15–18 days after the end of MPH treatment LTP remained strongly enhanced.•Five months later LTP was no longer ...augmented.•Could not be induced after high MPH doses.•Doses of MPH that improved maze-learning also enhanced LTP in the same animals.
Methylphenidate (MPH) is widely used as a “nootropic” agent and in the treatment of disorders of attention, and has been shown to modulate synaptic plasticity in vitro. Here we present in vivo evidence that this MPH-induced metaplasticity can last long after the end of treatment. MPH (0, 0.2, 1 and 5mg/kg) was administered daily to male rats from postnatal day 42 for 15 days. The animals were tested daily in a radial maze. Long-term potentiation (LTP), a marker of neural plasticity, was induced in vivo in the prefrontal cortex after 2–3h, 15–18 days or 5 months without treatment. The behavioral performance of the 1mg/kg group improved, while that of animals that had received 5mg/kg deteriorated. In the 1 and 5mg/kg groups LTP induced 2–3h after the last MPH treatment was twice as large as in the controls. Further, 15–18 days after the last MPH administration, in groups receiving 1 and 5mg/kg, LTP was about fourfold higher than in controls. However, 5 months later, LTP in the 1mg/kg group was similar to controls and in the 5mg/kg group LTP could not be induced at all. No significant changes of LTP were seen in the low-dose group of animals (0.2mg/kg). Thus, firstly, doses of MPH that improve learning coincide approximately with those that augment LTP. Secondly, MPH-induced increases in LTP can last for several weeks, but these may disappear over longer periods or deteriorate at high doses.
It has previously been demonstrated that the risk of hypoglycemia is low among otherwise healthy elderly fasted patients with type 2 diabetes taking oral sulfonylurea medications. Nevertheless, these ...agents do cause hypoglycemia in clinical practice, suggesting that accompanying factors must typically be present for hypoglycemia to occur. Ethanol is one putative risk factor that has not been evaluated as a mechanism for low blood glucose among sulfonylurea users. We hypothesized that low concentrations of ethanol would reduce blood glucose concentrations in elderly type 2 diabetic patients receiving sulfonylureas during a short-term fast.
A total of 10 type 2 diabetic patients, aged 68 +/- 3 years and receiving 20 mg glyburide daily, participated in a prospective double-blind placebo-controlled in-patient study consisting of two 24-h fasts at least 1 week apart. During hours 14 and 15 of the fasting studies, subjects received intravenous infusions of either 4.35 mmol.kg-1.h-1 ethanol (equivalent to one or two alcoholic beverages) or saline placebo in random order. Ethanol, plasma glucose, insulin, and counterregulatory hormones were assessed very 30-60 min during the final 10 h of the fast.
Blood ethanol levels peaked at 17 +/- 2 mmol/l (the lower legal limit of intoxication in New Mexico) during the ethanol study. Plasma glucose concentrations did not differ at baseline (placebo 8.5 +/- 1.8 vs. ethanol 8.7 +/- 1.7 mmol/l; P = 0.50), but nadir plasma glucose was lower after the ethanol infusion compared with placebo (4.4 +/- 1.2 vs. 5.0 +/- 1.4 mmol/l; P = 0.01), and the absolute decline in plasma glucose was also greater during the ethanol study than the placebo study (4.7 +/- 0.9 vs. 3.6 +/- 1.2 mmol/l; P = 0.01). Counterregulatory hormone levels were increased during the ethanol study and nonesterified fatty acid concentrations were suppressed compared with the placebo study.
Low doses of ethanol predispose fasted elderly type 2 diabetic patients to low blood glucose during a short-term fast. This may be one of several mechanisms by which sulfonylurea-induced hypoglycemia occurs in elderly patients.
Lispro is a new rapidly absorbed insulin analog. At present, there are no recommendations for the optimal injection time of lispro insulin in hyperglycemic patients. In contrast to normoglycemic ...patients with diabetes, we hypothesized that injection of lispro insulin 15-30 min before meal ingestion would improve postprandial glucose excursion in hyperglycemic diabetic subjects.
In 48 randomized overnight studies, 12 healthy adult type 1 diabetic patients received lispro insulin 0.15 U/kg admixed with human ultralente 0.2 U/kg (as background insulin) subcutaneously at minutes (-30, -15, 0, and +15) relative to the ingestion of an American Diabetes Association breakfast of 8.6 kcal/kg. Pre-breakfast hyperglycemia of 10.2 +/- 0.2 mmol/l was established before the study by continuous overnight infusion of intravenous insulin, which was stopped 30 min before lispro insulin injection. Glucose and insulin levels were measured every 30 min for 5 h after breakfast.
Results demonstrated that postprandial glucose excursion was reduced when lispro insulin was administered 15 or 30 min before the meal compared with lispro insulin injected at the meal (P < 0.002). The postprandial glucose excursion (millimoles per liter per hour) was -6.4 +/- 3 for the -30-min group, -5.1 +/- 2.9 for the -15-min group, 3.4 +/- 4.1 for the 0-min group, and 5.7 +/- 4.4 for the +15-min group. Although injecting lispro insulin at 30 min before the meal resulted in a significant reduction in postprandial glycemia, it was accompanied by loss of glucose control at 4 h postmeal in two subjects.
Optimization of lispro insulin in hyperglycemic patients requires timing of the insulin injection at least 15 min before the meal.
Acamprosate (calciumacetylhomotaurinate) is used therapeutically against relapse in weaned alcoholics. In the present study, the mechanism of action was investigated by making intracellular in vitro ...and extracellular in vivo recordings from rat neocortical neurons. Acamprosate (0.1-1 mM) added to the perfusion fluid in vitro reduced excitatory and inhibitory postsynaptic potentials and the depolarizing responses evoked by iontophoretic application of the excitatory amino acids, L-glutamate, L-aspartate, L-homocysteate and N-methyl-D-aspartate, but did not alter the responses to gamma-aminobutyric acid. Acamprosate decreased electrical excitability without apparently changing membrane potential, input resistance, afterhyperpolarization, or threshold and amplitude of the action potential. In vivo iontophoretic application of acamprosate reduced the extracellularly recorded unit activity elicited by iontophoretically applied L-glutamate, whereas spontaneous discharges remained unaffected. These data suggest that acamprosate reduces the postsynaptic efficacy of excitatory amino acid neurotransmitters and lowers neuronal excitability in the neocortex of the rat.
Effects of interleukin-1
β (bath-applied; 500 pM) on rat hippocampal CA3 pyramidal and dentate granule cells were studied using intracellular microelectrode recording in vitro. In both cell types ...membrane input resistance, resting membrane potential and action potential amplitude remained stable throughout. No change was seen in postsynaptic potentials in granule cells. After blocking excitatory synaptic transmission in CA3 pyramids interleukin-1
β was found to consistently decrease synaptic inhibition by about 30%.
Effects of the antiepileptic drug sodium valproate (VPA) were studied on neocortical pyramidal cells (layer II/III) of the rat in vitro by intracellular recording. VPA (0.1-1 mM) in a dose-related ...manner suppressed the characteristic transient depolarizations induced by N-methyl-D-aspartate (NMDA) applied iontophoretically Higher concentrations of VPA (5-10 mM) also reduced L-glutamate responses. At these concentrations VPA increased the duration of orthodromically evoked inhibitory postsynaptic potentials and reduced repetitive spike firing induced by depolarizing currents. All effects were fully reversible within about 30 min. These results suggest that an essential mode of action for the anticonvulsant VPA is the attenuation of NMDA receptor-mediated excitation.
Risks of Complication Following Thyroidectomy Burge, Mark R.; Zeise, Tanja‐Maria; Johnsen, Michael W. ...
Journal of general internal medicine,
January 1998, 1998, 1998-Jan, 1998-1-00, 19980101, Letnik:
13, Številka:
1
Journal Article, Conference Proceeding
Recenzirano
Odprti dostop
OBJECTIVE:
Because hypoparathyroidism is a serious complication of thyroidectomy, we attempted to elucidate factors determining the risk of this postoperative outcome.
SETTING:
Four tertiary care ...hospitals in Albuquerque, New Mexico.
PATIENTS:
A retrospective study of 142 patients who underwent total or subtotal thyroidectomy between 1988 and 1995.
MEASUREMENTS AND MAIN RESULTS:
Permanent hypoparathyroidism was defined as hypocalcemic symptoms plus a requirement for oral vitamin D or calcium 6 months after thyroidectomy. Factors analyzed to determine their contribution to the risk of persistent postoperative hypoparathyroidism were the indication for thyroidectomy, performance of a preoperative thyroid needle biopsy, type of surgery, postoperative pathology, presence and stage of thyroid carcinoma, resident surgeon involvement, and specialty of the surgeon performing the procedure. Surgical specialty and stage of thyroid carcinoma were independent risk factors for persistent postoperative hypoparathyroidism by multivariate analysis. Nine (29%) of 31 patients who had thyroidectomy by otolaryngologists met criteria for permanent hypoparathyroidism, and 6 (5%) of 111 patients who had thyroidectomy by general surgeons met the same criteria ( p < .001). Adjustment for the effect of stage did not eliminate the effect of specialty ( p= .006), and adjustment for the effect of specialty did not eliminate the effect of stage ( p= .02), on the occurrence of postoperative hypoparathyroidism.
CONCLUSIONS:
We conclude from our data that patients undergoing thyroidectomy by an otolaryngologist may be at a higher risk of permanent postoperative hypoparathyroidism than patients who undergo thyroidectomy by a general surgeon. This may reflect differences in case selection or surgical approach or both.
KEY WORDS:
thyroidectomy; surgical complications; hypoparathyroidism; hypocalcemia; thyroid carcinoma.
Previous studies using high-resistance sharp electrodes demonstrated that corticosterone (CORT) reduced GABAergic synaptic inhibition in CA1 neurons of the rat hippocampas in vitro. In the present ...study we used whole-cell gigaseal recordings to investigate the possible role of cytosolic factors in the transduction mechanism underlying this action. The perturbation of the intracellular milieu that occurs under these recording conditions abolished the CORT-induced decrease in inhibitory postsynaptic conductance. CORT actually increased GABA
A receptor-mediated conductances in about 50% of the neurons tested when the whole-cell recording mode was employed. As in the high-resistance microelectrode studies, CORT did not change the resting membrane potential, action potential amplitude or input resistance. The results suggest that the reduction of GABAergic synaptic inhibition in hippocampal CA1 pyramidal neurons induced by CORT critically depends on the presence of cytosolic factors, which wash out during whole-cell gigaseal recordings.
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