The PCP site of the NMDA receptor complex

Vices-paradox in trauma: Positive alcohol and drug screens associated with decreased mortality

BACKGROUND

Improved survival in trauma patients with acute alcohol intoxication has been previously reported. The effect of illegal and controlled substances on mortality is less clear. We hypothesized that alcohol, illegal and controlled substances are each independently associated with lower odds of mortality in adult trauma patients.

METHODS

The Trauma Quality Improvement Program (2010-2016) was queried for patients screening positive for alcohol, illegal or controlled substances on admission. A multivariate logistic regression analysis was used to determine odds of mortality. A similar analysis was used after stratification by injury severity scale (ISS).

RESULTS

From 1,299,705 adult patients, 660,135 were screened for substance use. Of these patients, 497,872 were male, 227,995 (34.5 %) screened positive for alcohol, 155,437 (23.5 %) for illegal substances and 90,259 (13.7 %) for controlled substances. Mortality rate was 6.2 % with alcohol, 5.1 % with illegal substances, and 5.7 % with controlled substances compared to 8.0 % with no substance use (p < 0.001). After controlling for covariates, all groups had lower odds of mortality: alcohol (OR = 0.88, CI = 0.84-0.92, p < 0.001), illegal substances (OR = 0.83, CI = 0.77-0.90, p < 0.001), controlled substances (OR = 0.72, CI = 0.67-0.79, p < 0.001). When stratified by ISS, alcohol and illegal substances continued to be associated with decreased mortality until ISS 50. Controlled substances were associated with decreased mortality when ISS > 16.

CONCLUSION

Patients positive for alcohol, illegal or controlled substances have 12 %, 17 %, and 28 % decreased odds of mortality, respectively. This paradoxical association should be confirmed with future clinical studies and merits basic science research to identify biochemical or physiological components conferring a protective effect on survival in trauma patients.

Gender dimorphism in aspartame-induced impairment of spatial cognition and insulin sensitivity

Previous studies have linked aspartame consumption to impaired retention of learned behavior in rodents. Prenatal exposure to aspartame has also been shown to impair odor-associative learning in guinea pigs; and recently, aspartame-fed hyperlipidemic zebrafish exhibited weight gain, hyperglycemia and acute swimming defects. We therefore investigated the effects of chronic lifetime exposure to aspartame, commencing in utero, on changes in blood glucose parameters, spatial learning and memory in C57BL/6J mice. Morris Water Maze (MWM) testing was used to assess learning and memory, and a random-fed insulin tolerance test was performed to assess glucose homeostasis. Pearson correlation analysis was used to investigate the associations between body characteristics and MWM performance outcome variables. At 17 weeks of age, male aspartame-fed mice exhibited weight gain, elevated fasting glucose levels and decreased insulin sensitivity compared to controls (P<0.05). Females were less affected, but had significantly raised fasting glucose levels. During spatial learning trials in the MWM (acquisition training), the escape latencies of male aspartame-fed mice were consistently higher than controls, indicative of learning impairment. Thigmotactic behavior and time spent floating directionless was increased in aspartame mice, who also spent less time searching in the target quadrant of the maze (P<0.05). Spatial learning of female aspartame-fed mice was not significantly different from controls. Reference memory during a probe test was affected in both genders, with the aspartame-fed mice spending significantly less time searching for the former location of the platform. Interestingly, the extent of visceral fat deposition correlated positively with non-spatial search strategies such as floating and thigmotaxis, and negatively with time spent in the target quadrant and swimming across the location of the escape platform. These data suggest that lifetime exposure to aspartame, commencing in utero, may affect spatial cognition and glucose homeostasis in C57BL/6J mice, particularly in males.

In vitro and in vivo characterization of a novel negative allosteric modulator of neuronal nAChRs

In this study, we compared the in vitro and in vivo neuronal nicotinic acetylcholine receptor (nAChR) properties of 1,2,3,3a,4,8b-hexahydro-2-benzyl-6-N,N-dimethylamino-1-methylindeno[1,2,-b]pyrrole (HDMP, 4) to that of negative allosteric modulator (NAM), PCP. Patch-clamp experiments showed that HDMP exhibited an inhibitory functional activity at α7 nAChRs with an IC(50) of 0.07 μM, and was 357- and 414-fold less potent at α4β2 and α3β4 nAChRs, with IC(50)s of 25.1 and 29.0 μM, respectively. Control patch-clamp experiments showed that PCP inhibited α7, α4β2 and α3β4 nAChRs with IC(50)s of to 1.3, 29.0 and 6.4 μM, respectively. Further, HDMP did not exhibit any appreciable binding affinity to either α7 or α4β2 nAChRs, suggesting its action via a non-competitive mechanism at these neuronal nAChR subtypes. The in vivo study showed that HDMP was a potent antagonist of nicotine-induced analgesia in the tail-flick (AD(50)=0.008 mg/kg), but not in the hot-plate test. All together, our in vitro and in vivo data suggest that HDMP is a novel NAM of neuronal nAChRs with potent inhibitory activity at α7 nAChR subtype at concentrations ≤ 1μM that are not effective for α4β2 and α3β4 nAChRs.

Repeated postnatal phencyclidine administration in female juvenile rat delays onset of puberty but has no effect on pentylenetetrazol-induced seizure-susceptibility

The effects of chronic phencyclidine (PCP) treatment on sexual maturation and seizure-susceptibility in the developing female rat were studied. Postnatal female rats were injected once daily with 5 mg/kg PCP from Day 5 till Day 15 and were observed for sexual maturation--vaginal opening and estrus cyclicity were used as indices of sexual maturation. PCP-treated rats showed a delay in both vaginal opening and in estrus cyclicity compared to saline-treated pair-fed controls. On postnatal Day 21, PCP-treated rats and saline-treated controls were tested for seizure-susceptibility using the pentylenetetrazol (PTZ)-induced seizure paradigm. PCP-treated female rats did not differ from saline-treated controls in their susceptibility to PTZ-induced seizures. In conclusion, chronic PCP administration during development in female rats disrupts sexual maturation but has no short-term effect on seizure susceptibility.

Laminar distribution of NMDA receptors in cat and monkey visual cortex visualized by [3H]-MK-801 binding

Glutamate is the major excitatory neurotransmitter of the mammalian central nervous system. Two major classes of glutamate receptors have been reported. The actions of glutamate on its N-methyl-D-aspartate (NMDA)-type receptor may underlie developmental and adult plasticity as well as neurotoxicity. The NMDA-type of glutamate receptor in cat and monkey visual cortex was visualized by means of in vitro receptor autoradiography with the noncompetitive NMDA-receptor antagonist [3H]-MK-801. The kinetics, performed on tissue sections, revealed an apparently single, saturable site with an approximate dissociation constant (KD) of 18.5 nM in cat and 15.9 nM in monkey visual cortex. Autoradiography, performed on frontal sections of cat and monkey visual cortex, revealed a heterogeneous laminar distribution of NMDA receptors. Cat areas 17, 18, 19, and the lateral suprasylvian areas exhibited a similar NMDA-receptor distribution. In these areas, NMDA receptors were most prominent in layer II and the upper part of layer III. In monkey striate cortex, NMDA receptors were primarily concentrated in layers II, upper III, IVc, V, and VI. In monkey secondary visual cortex, [3H]-MK-801 labeling was most prominent in layers II, V, and VI; whereas in the temporal visual areas included in this study layer II displayed the heaviest receptor labeling. In neither cat nor monkey could we observe significant differences in NMDA-receptor distribution between different retinotopic subdivisions within a single visual area. Neither did we detect any periodic changes in NMDA-receptor distribution that would correspond to the compartments defined by cytochrome-oxidase in monkey V1 and V2.

Protection against dendrotoxin-induced clonic seizures in mice by anticonvulsant drugs

Various anticonvulsant drugs were evaluated for their ability to protect against clonic seizures induced in mice by intraventricular injection of the K+ channel blocking peptide dendrotoxin (DTX). Phenytoin, the phenytoin-like anticonvulsant carbamazepine and the broad spectrum drug valproate were effective in this model, whereas the GABA-enhancers diazepam and tiagabine, the NMDA antagonists (+/-)-CPP and (+)-MK-801, the AMPA antagonist NBQX, the antiabsence drug ethosuximide and the Ca2+ channel antagonist nimodipine were inactive. In contrast to the lack of activity of other NMDA antagonists, phencyclidine and ADCI [(+/-)-aminocarbonyl-10,11-dihydro-5H-dibenzo [a,d]cyclohepten-5,10-imine] were potent antagonists of DTX-induced seizures.

Effects of anticonvulsant drugs on 4-aminopyridine-induced seizures in mice

The K+ channel blocker 4-aminopyridine (4-AP) causes epileptiform activity in in vitro preparations and is a potent convulsant in animals and man. In mice, 4-AP produces behavioral activation, clonic limb movements and wild running, followed by tonic hindlimb extension and death (ED97, 13.3 mg/kg, s.c.). We evaluated the ability of a series of anticonvulsant drugs to protect against 4-AP-induced seizures using lethality as the endpoint. Drugs with a phenytoin-like profile of activity were protective with ED50 values (all in mg/kg, i.p.) of 34.4 for phenytoin, 18.6 for carbamazepine, 26.9 for felbamate, and 41.5 for zonisamide. Phenobarbital and valproate also protected against 4-AP-induced seizures and lethality (ED50s, 30.6 and 301, respectively). In contrast the NMDA antagonists (+/-)-CPP and (+)-MK-801 were inactive as were the GABA enhancers diazepam, vigabatrin and tiagabine; the antiabsence drug ethosuximide; and the L-type Ca2+ channel blocker nimodipine. We conclude that drugs like phenytoin which block seizure spread are effective antagonists of seizures induced by K+ channel blockade. Drugs with specific actions on other cellular targets may be weak or inactive, presumably because they are unable to attenuate the spread of intense (non-NMDA receptor mediated) excitation evoked by 4-AP.