Impact of a Neuroscience-Based Health Education Course on High School Students' Health Knowledge, Beliefs, and Behaviors.

PURPOSE: The purpose of this pilot study was to evaluate the potential of an innovative high school neuroscience-based health course for implementation feasibility and impact on student outcomes. METHODS: Thirteen teachers from two high schools participated in this quasi-experimental pilot study including 395 students (202 in the intervention classes and 193 in the comparison classes). Students completed pre/post online surveys assessing their knowledge, beliefs, and behaviors. Our analysis strategy for multi-item measures was to estimate the effects of the intervention on latent change scores in structural equation models. RESULTS: Students in the neuroscience health classes showed a significant increase in neuroscience knowledge as compared to students in the comparison group (difference estimate in proportion correct metric, adjusted for covariates = .04; 95% confidence interval [.01, .06]). However, none of the other primary outcomes showed a significant difference between conditions. Teachers in the intervention group were observed implementing the neuroscience and health components more often than the self-regulation and growth mindset components. Students in the neuroscience group were more likely to mention the importance of caring for their brain and its link to health behaviors. CONCLUSIONS: Findings demonstrate that information about the link between health behaviors and brain functioning can be successfully integrated into a high school health education course, although effects on student health beliefs and behaviors were not observed. Additional development work should focus on clarifying the theoretical mechanisms of change, integrating the neuroscience content with self-regulation and growth mindset, and providing additional professional development for teachers.

Adolescent Intermittent Alcohol Exposure: Dysregulation of Thrombospondins and Synapse Formation are Associated with Decreased Neuronal Density in the Adult Hippocampus.

BACKGROUND: Adolescent intermittent alcohol exposure (AIE) has profound effects on neuronal function. We have previously shown that AIE causes aberrant hippocampal structure and function that persists into adulthood. However, the possible contributions of astrocytes and their signaling factors remain largely unexplored. We investigated the acute and enduring effects of AIE on astrocytic reactivity and signaling on synaptic expression in the hippocampus, including the impact of the thrombospondin (TSP) family of astrocyte-secreted synaptogenic factors and their neuronal receptor, alpha2delta-1 (α2δ-1). Our hypothesis is that some of the influences of AIE on neuronal function may be secondary to direct effects on astrocytes. METHODS: We conducted Western blot analysis on TSPs 1 to 4 and α2δ-1 from whole hippocampal lysates 24 hours after the 4th and 10th doses of AIE, then 24 days after the last dose (in adulthood). We used immunohistochemistry to assess astrocyte reactivity (i.e., morphology) and synaptogenesis (i.e., colocalization of pre- and postsynaptic puncta). RESULTS: Adolescent AIE reduced α2δ-1 expression, and colocalized pre- and postsynaptic puncta after the fourth ethanol (EtOH) dose. By the 10th dose, increased TSP2 levels were accompanied by an increase in colocalized pre- and postsynaptic puncta, while α2δ-1 returned to control levels. Twenty-four days after the last EtOH dose (i.e., adulthood), TSP2, TSP4, and α2δ-1 expression were all elevated. Astrocyte reactivity, indicated by increased astrocytic volume and area, was also observed at that time. CONCLUSIONS: Repeated EtOH exposure during adolescence results in long-term changes in specific astrocyte signaling proteins and their neuronal synaptogenic receptor. Continued signaling by these traditionally developmental factors in adulthood may represent a compensatory mechanism whereby astrocytes reopen the synaptogenic window and repair lost connectivity, and consequently contribute to the enduring maladaptive structural and functional abnormalities previously observed in the hippocampus after AIE.

Adolescent intermittent alcohol exposure: persistence of structural and functional hippocampal abnormalities into adulthood.

BACKGROUND: Human adolescence is a crucial stage of neurological development during which ethanol (EtOH) consumption is often at its highest. Alcohol abuse during adolescence may render individuals at heightened risk for subsequent alcohol abuse disorders, cognitive dysfunction, or other neurological impairments by irreversibly altering long-term brain function. To test this possibility, we modeled adolescent alcohol abuse (i.e., intermittent EtOH exposure during adolescence [AIE]) in rats to determine whether adolescent exposure to alcohol leads to long-term structural and functional changes that are manifested in adult neuronal circuitry. METHODS: We specifically focused on hippocampal area CA1, a brain region associated with learning and memory. Using electrophysiological, immunohistochemical, and neuroanatomical approaches, we measured post-AIE changes in synaptic plasticity, dendritic spine morphology, and synaptic structure in adulthood. RESULTS: We found that AIE-pretreated adult rats manifest robust long-term potentiation, induced at stimulus intensities lower than those required in controls, suggesting a state of enhanced synaptic plasticity. Moreover, AIE resulted in an increased number of dendritic spines with characteristics typical of immaturity. Immunohistochemistry-based analysis of synaptic structures indicated a significant decrease in the number of co-localized pre- and postsynaptic puncta. This decrease is driven by an overall decrease in 2 postsynaptic density proteins, PSD-95 and SAP102. CONCLUSIONS: Taken together, these findings reveal that repeated alcohol exposure during adolescence results in enduring structural and functional abnormalities in the hippocampus. These synaptic changes in the hippocampal circuits may help to explain learning-related behavioral changes in adult animals preexposed to AIE.

Effect of sub-chronic intermittent ethanol exposure on spatial learning and ethanol sensitivity in adolescent and adult rats.

It has become clear that adolescence is a period of distinct responsiveness to the acute effects of ethanol on learning and other cognitive functions. However, the effects of repeated intermittent ethanol exposure during adolescence on learning and cognition are less well studied, and other effects of repeated ethanol exposure such as withdrawal and chronic tolerance complicate such experiments. Moreover, few studies have compared the effects of repeated ethanol exposure during adolescence and adulthood, and they have yielded mixed outcomes that may be related to methodological differences and/or secondary effects of ethanol on behavioral performance. One emerging question is whether relatively brief intermittent ethanol exposure (i.e., sub-chronic exposure) during adolescence or adulthood might alter learning at a time after exposure when chronic tolerance would be expected, and whether tolerance to the cognitive effects of ethanol might influence the effect of ethanol on learning at that time. To address this, male adolescent and adult rats were pre-treated with sub-chronic daily ethanol (five doses [4.0 g/kg, i.p.] or saline at 24-h intervals, across 5 days). Two days after the last pre-exposure, spatial learning was assessed on 4 consecutive days using the Morris water maze. Half of the animals from each treatment cell received ethanol (2.0 g/kg, i.p.) 30 min prior to each testing session and half of the animals received saline. Ethanol pre-exposure altered water maze performance in adult animals but not in adolescents, and acute ethanol exposure impaired learning in animals of both ages independent of pre-exposure condition. There was no evidence of cognitive tolerance in animals of either age group. These results indicate that a relatively short period of intermittent ethanol exposure during adulthood, but not adolescence, promotes thigmotaxis in the water maze shortly after pre-exposure but does not induce cognitive tolerance to the effects of ethanol in either age group.

In vitro electrophoresis and in vivo electrophysiology of peripheral nerve using DC field stimulation.

BACKGROUND: Given the movement of molecules within tissue that occurs naturally by endogenous electric fields, we examined the possibility of using a low-voltage DC field to move charged substances in rodent peripheral nerve in vitro. NEW METHOD: Labeled sugar- and protein-based markers were applied to a rodent peroneal nerve and then a 5-10 V/cm field was used to move the molecules within the extra- and intraneural compartments. Physiological and anatomical nerve properties were also assessed using the same stimulation in vivo. RESULTS: We demonstrate in vitro that charged and labeled compounds are capable of moving in a DC field along a nerve, and that the same field applied in vivo changes the excitability of the nerve, but without damage. CONCLUSIONS: The results suggest that low-voltage electrophoresis could be used to move charged molecules, perhaps therapeutically, safely along peripheral nerves.

Effects of acute or chronic ethanol exposure during adolescence on behavioral inhibition and efficiency in a modified water maze task.

Ethanol is well known to adversely affect frontal executive functioning, which continues to develop throughout adolescence and into young adulthood. This is also a developmental window in which ethanol is misused by a significant number of adolescents. We examined the effects of acute and chronic ethanol exposure during adolescence on behavioral inhibition and efficiency using a modified water maze task. During acquisition, rats were trained to find a stable visible platform onto which they could escape. During the test phase, the stable platform was converted to a visible floating platform (providing no escape) and a new hidden platform was added in the opposite quadrant. The hidden platform was the only means of escape during the test phase. In experiment 1, adolescent animals received ethanol (1.0 g/kg) 30 min before each session during the test phase. In experiment 2, adolescent animals received chronic intermittent ethanol (5.0 g/kg) for 16 days (PND30 To PND46) prior to any training in the maze. At PND72, training was initiated in the same modified water maze task. Results from experiment 1 indicated that acute ethanol promoted behavioral disinhibition and inefficiency. Experiment 2 showed that chronic intermittent ethanol during adolescence appeared to have no lasting effect on behavioral disinhibition or new spatial learning during adulthood. However, chronic ethanol did promote behavioral inefficiency. In summary, results indicate that ethanol-induced promotion of perseverative behavior may contribute to the many adverse behavioral sequelae of alcohol intoxication in adolescents and young adults. Moreover, the long-term effect of adolescent chronic ethanol exposure on behavioral efficiency is similar to that observed after chronic exposure in humans.

Long-term modulation of A-type K(+) conductances in hippocampal CA1 interneurons in rats after chronic intermittent ethanol exposure during adolescence or adulthood.

BACKGROUND: Chronic alcohol use, especially exposure to alcohol during adolescence or young adulthood, is closely associated with cognitive deficits that may persist into adulthood. Therefore, it is essential to identify possible neuronal mechanisms underlying the observed deficits in learning and memory. Hippocampal interneurons play a pivotal role in regulating hippocampus-dependent learning and memory by exerting strong inhibition on excitatory pyramidal cells. The function of these interneurons is regulated not only by synaptic inputs from other types of neurons but is also precisely governed by their own intrinsic membrane ionic conductances. The voltage-gated A-type potassium current (IA ) regulates the intrinsic membrane properties of neurons, and disruption of IA is responsible for many neuropathological processes including learning and memory deficits. Thus, it represents a previously unexplored cellular mechanism whereby chronic ethanol (EtOH) may alter hippocampal memory-related functioning. METHODS: Using whole-cell electrophysiological recording methods, we investigated the enduring effects of chronic intermittent ethanol (CIE) exposure during adolescence or adulthood on IA in rat CA1 interneurons. RESULTS: We found that the mean peak amplitude of IA was significantly reduced after CIE in either adolescence or adulthood, but IA density was attenuated after CIE in adolescence but not after CIE in adulthood. In addition, the voltage-dependent steady-state activation and inactivation of IA were altered in interneurons after CIE. CONCLUSIONS: These findings suggest that CIE can cause long-term changes in IA channels in interneurons and thus may alter their inhibitory influences on memory-related local hippocampal circuits, which could be, in turn, responsible for learning and memory impairments observed after chronic EtOH exposure.

Long-term effects of chronic intermittent ethanol exposure in adolescent and adult rats: radial-arm maze performance and operant food reinforced responding.

BACKGROUND: Adolescence is not only a critical period of late-stage neurological development in humans, but is also a period in which ethanol consumption is often at its highest. Given the prevalence of ethanol use during this vulnerable developmental period we assessed the long-term effects of chronic intermittent ethanol (CIE) exposure during adolescence, compared to adulthood, on performance in the radial-arm maze (RAM) and operant food-reinforced responding in male rats. METHODOLOGY/PRINCIPAL FINDINGS: Male Sprague Dawley rats were exposed to CIE (or saline) and then allowed to recover. Animals were then trained in either the RAM task or an operant task using fixed- and progressive- ratio schedules. After baseline testing was completed all animals received an acute ethanol challenge while blood ethanol levels (BECs) were monitored in a subset of animals. CIE exposure during adolescence, but not adulthood decreased the amount of time that animals spent in the open portions of the RAM arms (reminiscent of deficits in risk-reward integration) and rendered animals more susceptible to the acute effects of an ethanol challenge on working memory tasks. The operant food reinforced task showed that these effects were not due to altered food motivation or to differential sensitivity to the nonspecific performance-disrupting effects of ethanol. However, CIE pre-treated animals had lower BEC levels than controls during the acute ethanol challenges indicating persistent pharmacokinetic tolerance to ethanol after the CIE treatment. There was little evidence of enduring effects of CIE alone on traditional measures of spatial and working memory. CONCLUSIONS/SIGNIFICANCE: These effects indicate that adolescence is a time of selective vulnerability to the long-term effects of repeated ethanol exposure on neurobehavioral function and acute ethanol sensitivity. The positive and negative findings reported here help to further define the nature and extent of the impairments observed after adolescent CIE and provide direction for future research.

Binge-pattern ethanol exposure during adolescence, but not adulthood, causes persistent changes in GABAA receptor-mediated tonic inhibition in dentate granule cells.

BACKGROUND: In recent years, it has become clear that acute ethanol (EtOH) affects various neurobiological and behavioral functions differently in adolescent animals than in adults. However, less is known about the long-term neural consequences of chronic EtOH exposure during adolescence, and most importantly whether adolescence represents a developmental period of enhanced vulnerability to such effects. METHODS: We made whole-cell recordings of GABAA receptor-mediated tonic inhibitory currents from dentate gyrus granule cells (DGGCs) in hippocampal slices from adult rats that had been treated with chronic intermittent ethanol (CIE) or saline during adolescence, young adulthood, or adulthood. RESULTS: CIE reduced baseline tonic current amplitude in DGGCs from animals pretreated with EtOH during adolescence, but not in GCs from those pretreated with EtOH during young adulthood or adulthood. Similarly, the enhancement of tonic currents by acute EtOH exposure ex vivo was increased in GCs from animals pretreated with EtOH during adolescence, but not in those from animals pretreated during either of the other 2 developmental periods. CONCLUSIONS: These findings underscore our recent report that CIE during adolescence results in enduring alterations in tonic current and its acute EtOH sensitivity and establish that adolescence is a developmental period during which the hippocampal formation is distinctively vulnerable to long-term alteration by chronic EtOH exposure.

Effects of ethanol, Δ(9)-tetrahydrocannabinol, or their combination on object recognition memory and object preference in adolescent and adult male rats.

Recent advances have been made in our understanding of the deleterious effects of both ethanol and THC on adolescent behavior and brain development. However, very little is known about the combined effects of EtOH+THC during adolescence, a time in which these drugs are often used together. The purpose of this experiment was to: (1) determine whether EtOH and/or THC induced greater working memory impairment in adolescent than adult male rats using the novel object recognition (NOR) task and (2) determine whether the EtOH+THC combination would produce a more potent additive effect in adolescents than adults when compared to these drugs alone. NOR was performed with a 24h delay under each of the four drug conditions: vehicle; 1.5g/kg ethanol; 1.0mg/kg THC; and 1.5g/kg EtOH+1.0mg/kg THC, at 72h intervals. The results show that there was an age effect on working memory in NOR after the EtOH+THC challenge. Specifically, adolescent animals showed a preference for the familiar object whereas adults showed no preference for the novel or familiar object, the latter being characteristic of a classic working memory deficit. These effects were not dependent on changes in exploration across session, global activity across drug condition, or total object exploration. These novel findings clearly indicate that further understanding of this age-drug interaction is crucial to elucidating the influence that adolescent EtOH+THC use may have on repeated drug use and abuse later in life.

In the rat, chronic intermittent ethanol exposure during adolescence alters the ethanol sensitivity of tonic inhibition in adulthood.

BACKGROUND: Alcohol drinking by adolescents is a major public health concern. Adolescents tend to drink in a chronic, intermittent, that is, "binge," pattern, and such patterns of ethanol exposure are associated with increased risk of neurotoxicity and the development of alcohol use disorders (Crews et al., 2000; Hunt, 1993). Both adolescent humans and rats are more sensitive to acute ethanol-induced memory impairment than adults (Acheson et al., 1998; Markwiese et al., 1998). Furthermore, in rats, chronic intermittent ethanol (CIE) exposure during adolescence produces a long-lasting, perhaps permanent, maintenance of the adolescent high sensitivity to ethanol's amnestic effects (White et al., 2000a). We have previously shown that acute ethanol increases tonic inhibitory current mediated by extrasynaptic GABA(A) receptors more efficaciously in dentate granule cells (DGCs) from adolescent than adult rats (Fleming et al., 2007). In this study, we determined if CIE during adolescence produced long-lasting changes in this tonic current. METHODS: Adolescent rats were subjected to a CIE exposure regimen and allowed to mature to full adulthood. Whole-cell voltage-clamp measurements of tonic inhibitory current and mean phasic current were made in vitro in hippocampal brain slices. RESULTS: CIE exposure during adolescence increased the ethanol sensitivity of tonic inhibitory current mediated by extrasynaptic GABA(A) receptors and decreased the ethanol sensitivity of phasic, synaptic GABA(A) receptor-mediated current in adult DGCs. CONCLUSIONS: CIE exposure during adolescence produces long-lasting changes in the function and ethanol sensitivity of extrasynaptic GABA(A) receptors in DGCs. These changes appear to "lock-in" and maintain the high adolescent sensitivity to ethanol in these cells. Furthermore, greater ethanol enhancement of tonic inhibition in the hippocampal formation after CIE is consistent with the greater sensitivity to ethanol-induced memory impairment after adolescent CIE. This finding represents the first demonstration of a long-term, memory-related cellular effect of CIE during adolescence, and the "lock-in" of adolescent ethanol sensitivity that these results suggest could represent a conceptual step forward in understanding the vulnerability of the adolescent brain to alcohol.

GABA transport modulates the ethanol sensitivity of tonic inhibition in the rat dentate gyrus.

In recent years, the effect of ethanol on tonic inhibition mediated by extrasynaptic GABA(A) receptors (GABA(A)Rs) has become a topic of intensive investigation and some controversy. The high ethanol sensitivity of extrasynaptic GABA(A) receptors containing the δ subunit combined with the role of tonic inhibition in maintaining the background inhibitory "tone" in hippocampal circuits has suggested that they may play a key role mediating certain behavioral effects of ethanol, including those related to learning and memory. We have found that ethanol disrupts learning and learning-related hippocampal function more potently in adolescent animals than in adults and that ethanol promotes extrasynaptic receptor-mediated GABAergic tonic currents more potently in adolescents than in adults. However, there have been no studies of potential mechanisms that may underlie the enhanced ethanol sensitivity of the tonic current in adolescents. In this study, we recorded GABA(A) receptor-mediated tonic currents in dentate gyrus granule cells in hippocampal slices from adolescent and adult rats. As previously reported, we found that ethanol potentiated the currents more efficaciously in cells from adolescents than in those from adults. We also found that the GAT-1 blocker NO-711 eliminated this developmental difference in ethanol sensitivity. These findings suggest that regulation of ambient GABA by GABA transporters may contribute to the difference in ethanol sensitivity between adolescents and adults.

The synthetic cannabinoid WIN 55212-2 differentially modulates thigmotaxis but not spatial learning in adolescent and adult animals.

Unlike Δ(9)-THC, the synthetic compound WIN 55212-2 (WIN) is a full agonist of endogenous cannabinoid receptors. Previous work has shown Δ(9)-THC to affect adolescent and adult animals differently on numerous behavioral measures of spatial memory, anxiety, and locomotor activity. However, far less is known about the developmental and neurobehavioral effects of WIN. To address this, we assessed the effect of WIN (1mg/kg) on spatial learning in adolescent and adult rats using the Morris water maze. While all animals demonstrated decreased swim distance across days, WIN affected adolescents and adults differently. It improved performance in adolescents and resulted in a nearly significant performance decrement in adults. However, these effects were significantly related to thigmotaxis, which declined across days in the water maze testing protocol. WIN reduced thigmotaxis on days 1 and 2 (but not days 3-5) only in adolescents. The effect of age, treatment, and the age×treatment interaction was eliminated after controlling for thigmotaxis. These results indicate that WIN affects thigmotaxis rather than spatial reference memory. More importantly, these findings indicate a dissociation between the developmental effects of THC and the synthetic CB1 receptor agonist, WIN 55212-2. We suggest that the role of thigmotaxis be carefully evaluated in future neurodevelopmental studies of spatial learning, especially those investigating the endocannabinoid system.

Dopamine attenuates evoked inhibitory synaptic currents in central amygdala neurons.

The central nucleus of the amygdala (CeA) plays a critical role in regulating the behavioral, autonomic and endocrine response to stress. Dopamine (DA) participates in mediating the stress response and DA release is enhanced in the CeA during stressful events. However, the electrophysiological effects of DA on CeA neurons have not yet been characterized. Therefore, the purpose of this study was to identify and characterize the effect of DA application on electrophysiological responses of CeA neurons in coronal brain sections of male Sprague-Dawley rats. We used whole-cell patch-clamp electrophysiological techniques to record evoked synaptic responses and to determine basic membrane properties of CeA neurons both before and after DA superfusion. DA (20-250 µM) did not significantly alter membrane conductance over the voltage range tested. However, DA significantly reduced the peak amplitude of evoked inhibitory synaptic currents in CeA neurons. Pretreatment with the D(2) receptor antagonist eticlopride failed to significantly block the inhibitory effects of DA. In contrast, pretreatment with the D(1) receptor antagonist SCH-23390 significantly reduced the effects of DA on evoked inhibitory neurotransmission in these neurons. Moreover, bath superfusion of the specific D(1) receptor agonist SKF-39393, but not the D(2) receptor agonist quinpirole, significantly reduced peak amplitude of evoked inhibitory synaptic events. DA reduced the frequency of miniature IPSCs without altering the amplitude, while having no effect on the amplitude of IPSCs elicited by pressure application of GABA. These results suggest that DA may modulate inhibitory synaptic transmission in CeA through D(1) receptor activation primarily by a presynaptic mechanism.

Role of cannabinoid receptor type 1 desensitization in greater tetrahydrocannabinol impairment of memory in adolescent rats.

Adolescence is a well defined developmental period during which marijuana use is common. However, little is known about the response to marijuana in adolescents compared with adults. We have shown previously that adolescent rats are more impaired than adults by Δ(9)-tetrahydrocannabinol (THC), the main psychoactive compound in marijuana, in a spatial learning task, but the mechanism responsible for this differential impairment is not understood. We determined the role of THC tolerance and cannabinoid receptor type 1 (CB1) regulation in THC-induced spatial learning impairment in adolescent and adult rats. We measured the development of tolerance to THC-induced learning impairment in adolescent (postnatal days 30-35) and adult (postnatal days 70-75) rats. We pretreated them for 5 days with 10 mg/kg THC, and then evaluated the effects of vehicle or THC treatment on learning during training in the Morris water maze. We also determined CB1 number and functional coupling in the hippocampus of adolescents and adults. Finally, we measured the time course of hippocampal CB1 desensitization in adolescents and adults during treatment with 10 mg/kg THC or vehicle. Our results indicate that adults, but not adolescents, become tolerant to the effects of THC during water maze training after 5 days of pretreatment. CB1s in adolescent hippocampus are less functionally coupled to G proteins and desensitize more slowly in response to THC treatment than those of adults. THC may impair learning in adolescents more than in adults because of delayed activation of cellular homeostatic adaptive mechanisms underlying cannabinoid tolerance in the hippocampus.

Differential sensitivity of hippocampal interneurons to ethanol in adolescent and adult rats.

Ethanol (EtOH) promotes GABAergic synaptic transmission in the central nervous system. We have shown that EtOH enhances the frequency of GABA(A) receptor-mediated spontaneous inhibitory postsynaptic currents less powerfully in hippocampal CA1 pyramidal neurons from adolescent animals compared with those from adults. However, we have also shown that EtOH promotes the firing of hippocampal interneurons, located in stratum lacunosum moleculare (SLM), from adolescent animals more potently than in those from adults. Thus the latter finding would seem to be inconsistent with the former. To understand this apparent inconsistency, we have now assessed the effects of EtOH on a different subpopulation of hippocampal interneurons, those with somata located in the stratum oriens (SO). We found that EtOH-induced enhancement of the frequency of spontaneous action potentials (sAPs) was less in interneurons from adolescent rats compared with those from adults. In addition, EtOH-induced reduction of the afterhyperpolarization decay time constant (τ(slow)) was less pronounced in interneurons from adolescent rats, as was the EtOH-induced increase in the amplitude of the hyperpolarization-activated cation current, I(h). The effect of EtOH on sAP firing frequency was blocked by application of the I(h) antagonist 4-ethylphenylamino-1,2-dimethyl-6-methylaminopyrimidinium chloride (ZD7288). These results indicate that although EtOH promotes the firing of hippocampal interneurons, through promotion of I(h), the developmental expression of this effect differs between interneurons with somata located in the SO and SLM.

Modulation of NMDA and AMPA-mediated synaptic transmission by CB1 receptors in frontal cortical pyramidal cells.

Although the endogenous cannabinoid system modulates a variety of physiological and pharmacological processes, the specific role of cannabinoid CB1 receptors in the modulation of glutamatergic neurotransmission and neural plasticity is not well understood. Using whole-cell patch clamp recording techniques, evoked or spontaneous excitatory postsynaptic currents (eEPSCs or sEPSCs) were recorded from visualized, layer II/III pyramidal cells in frontal cortical slices from rat brain. Bath application of the CB1 receptor agonist, WIN 55212-2 (WIN), reduced the amplitude of NMDA receptor-mediated EPSCs in a concentration-dependent manner. When co-applied with the specific CB1 antagonists, AM251 or AM281, WIN did not suppress NMDA receptor-mediated EPSCs. WIN also reduced the amplitude of evoked AMPA receptor-mediated EPSCs, an effect that was also reversed by AM251. Both the frequency and amplitude of spontaneous AMPA receptor-mediated EPSCs were significantly reduced by WIN. In contrast, WIN reduced the frequency, but not the amplitude of miniature EPSCs, suggesting that the suppression of glutamatergic activity by CB1 receptors in the frontal neocortex is mediated by a presynaptic mechanism. Taken together, these data indicate a critical role for endocannabinoid signaling in the regulation of excitatory synaptic transmission in frontal neocortex, and suggest a possible neuronal mechanism whereby THC regulates cortical function.

The novel micro-opioid receptor antagonist, [N-allyl-Dmt(1)]endomorphin-2, attenuates the enhancement of GABAergic neurotransmission by ethanol.

AIMS: We investigated the effects of [N-allyl-Dmt(1)]endomorphin-2 (TL-319), a novel and highly potent micro-opioid receptor antagonist, on ethanol (EtOH)-induced enhancement of GABA(A) receptor-mediated synaptic activity in the hippocampus. METHODS: Evoked and spontaneous inhibitory postsynaptic currents (eIPSCs and sIPSCs) were isolated from CA1 pyramidal cells from brain slices of male rats using whole-cell patch-clamp techniques. RESULTS: TL-319 had no effect on the baseline amplitude of eIPSCs or the frequency of sIPSCs. However, it induced a dose-dependent suppression of an ethanol-induced increase of sIPSC frequency with full reversal at concentrations of 500 nM and higher. The non-specific competitive opioid receptor antagonist naltrexone also suppressed EtOH-induced increases in sIPSC frequency but only at a concentration of 60 microM. CONCLUSION: These data indicate that blockade of micro-opioid receptors by low concentrations of [N-allyl-Dmt(1)]endomorphin-2 can reverse ethanol-induced increases in GABAergic neurotransmission and possibly alter its anxiolytic or sedative effects. This suggests the possibility that high potency opioid antagonists may emerge as possible candidate compounds for the treatment of ethanol addiction.

Developmental sensitivity of hippocampal interneurons to ethanol: involvement of the hyperpolarization-activated current, Ih.

Ethanol (EtOH) has powerful effects on GABA(A) receptor-mediated neurotransmission, and we have previously shown that EtOH-induced enhancement of GABA(A) receptor-mediated synaptic transmission in the hippocampus is developmentally regulated. Because synaptic inhibition is determined in part by the firing properties of interneurons, we have investigated the mechanisms whereby EtOH influences the spontaneous firing characteristics and hyperpolarization-activated cation current (Ih) of hippocampal interneurons located in the near to the border of stratum lacunosum moleculare and s. radiatum of adolescent and adult rats. EtOH did not affect current injection-induced action potentials of interneurons that do not exhibit spontaneous firing. However, in neurons that fire spontaneously, EtOH enhanced the frequency of spontaneous action potentials (sAPs) in a concentration-dependent manner, an effect that was more pronounced in interneurons from adolescent rats, compared with adult rats. EtOH also modulated the afterhyperpolarization (AHP) that follows sAPs by shortening the tau(slow) decay time constant, and this effect was more pronounced in slices from adolescent rats. EtOH increased Ih amplitudes, accelerated Ih activation kinetics, and increased the maximal Ih conductance in interneurons from animals in both age groups. These effects were also more pronounced in interneurons from adolescents and persisted in the presence of glutamatergic and GABAergic blockers. However, EtOH failed to affect sAP firing in the presence of ZD7288 or cesium chloride. These results suggest that Ih may be of mechanistic significance in the effect of EtOH on interneuron spontaneous firing.