• Energy Research

Ethanol can be a food source but its effects on energy balance and contribution to obesity remain inconclusive. In this study, we hypothesized that the effects of ethanol on energy intake and body weight would depend on the administration dose, pattern and the blood ethanol concentration (BEC) time-course. Experiment 1 examined changes in food intake, diet preference, and body weight after saline or ethanol (1 and 3g/kg) injection (IP). Experiment 2 compared the effects in rats that received either 3g/kg/day ethanol administered all at once (EtOH_S) or 2 1.5g/kg injections spaced by 3h (EtOH_D). Experiment 3 examined the effects of 7.5h/day, Mon through Fri for 8weeks, voluntary ethanol drinking (5% and 10% ethanol) on food intake and body weight. Results of Experiments 1 and 2 indicate that acute ethanol administrations dose-dependently reduced energy intake, high fat diet preference and weight gain. Acute 3g/kg ethanol injection in the EtOH_S group decreased energy intake, weight gain and visceral fat to a greater extent than in the EtOH_D group. Results of Experiment 3 show that male and female rats voluntarily drank 1.65-2.31g/kg ethanol within 3.5h with reduced chow intake but unchanged total energy intake and weight gain. Furthermore, 3g/kg ethanol injection resulted in BEC that remained at intoxicating levels e.g. >120mg/dL for several hours post-administration and was higher in the EtOH_S than in the EtOH_D group. In contrast, BEC in voluntarily drinking was ~67mg/dL and decreased to below 10mg/dL 5h after termination of ethanol access. Taken together, these data suggest that 3g/kg ethanol injection robustly suppresses appetite and weight gain due to the higher BECs attained. Furthermore, BEC attained and maintained is a determining factor for how ethanol administration affects appetite and long-term energy balance.

Alcohol and cannabis are often taken in combination, and extensive co-use has been linked to enduring changes in cognitive and metabolic functioning. The underlying mechanisms for these effects are unclear, but we recently demonstrated that co-administration of ethanol and delta-9-tetrahydrocannbinol (THC) to adolescent rats caused lasting adaptations in GABA and glycogen synthase kinase 3ß (GSK3ß) signaling in the medial prefrontal cortex (mPFC). As a ubiquitous protein kinase, GSK3ß is downstream to the protein kinase B (also known as AKT) pathway that is activated by insulin receptor signaling in a main control center for metabolism and energy homeostasis, the mediobasal hypothalamus (MBH). Our goal here was to investigate if volitional co-use of low to moderate levels of ethanol and THC would impact the total and phosphorylated levels (p) of AKT and GSK3ß in the mPFC and MBH. Peri-adolescent Long Evans rats [postnatal day (P) 30-47] consumed 10 % ethanol, cookies laced with THC (3-10 mg/kg/day), both drugs, or vehicle controls. On P114, we modeled re-exposure to a behaviorally relevant dose of THC by challenging rats (i.p.) with 5 mg/kg THC (or vehicle) and sacrificed them 30 min later. Western blot analysis revealed that THC challenge increased pAKT and pGSK3ß compared to control similarly across all treatment groups, sexes, and brain regions; no effects on total levels of AKT or GSK3ß were found. Previously reported behavioral results from these rats showed no differences in working memory assessed in adulthood. Although future studies will be necessary to determine the role of exposure dose on drug-induced adaptations in AKT and GSK3ß signaling, the current findings suggest that moderate volitional co-use of alcohol and THC may not produce long-term deficits that persist into adulthood.

AbstractThe increase in social acceptance and legalization of cannabis over the last several years is likely to increase the prevalence of its co-use with alcohol. In spite of this, the potential for effects unique to co-use of these drugs, especially in moderate doses, has been studied relatively infrequently. We addressed this in the current study using a laboratory rat model of voluntary drug intake. Periadolescent male and female Long-Evans rats were allowed to orally self-administer ethanol, Δ9-tetrahydrocannibinol (THC), both drugs, or their vehicle controls from postnatal day (P) 30 to P47. They were subsequently trained and tested on an instrumental behavior task that assesses attention, working memory and behavioral flexibility. Similar to previous work, consumption of THC reduced both ethanol and saccharin intake in both sexes. Blood samples taken 14h following the final self-administration session revealed that females had higher levels of the THC metabolite THC-COOH. There were modest effects of THC on our delayed matching to position (DMTP) task, with females exhibiting reduced performance compared to their control group or male, drug using counterparts. However, there were no significant effects of co-use of ethanol or THC on DMTP performance, and drug effects were also not apparent in the reversal learning phase of the task when non-matching to position was required as the correct response. These findings are consistent with other published studies in rodent models showing that use of these drugs in low to moderate doses does not significantly impact memory or behavioral flexibility following a protracted abstinence period.

ABSTRACTSignificant exposure to alcohol or cannabis during adolescence can induce lasting disruptions of neuronal signaling in brain regions that are later to mature, such as the medial prefrontal cortex (mPFC). Considerably less is known about the effects of alcohol and cannabis co-use, despite its common occurrence. Here, we used male and female Long-Evans rats to investigate the effects of early-life exposure to ethanol, delta-9-tetrahydrocannabinol (THC), or their combination on high frequency stimulation (HFS)-induced plasticity in the prelimbic region of the mPFC. Animals were injected daily from postnatal days 30 to 45 with vehicle or THC (escalating doses, 3-20 mg/kg) and allowed to drink vehicle (0.1% saccharin) or 10% ethanol immediately after each injection.In vitrobrain slice electrophysiology was then used to record population responses of layer V neurons following HFS in layer II/III after 3-4 weeks of abstinence. We found that THC exposure reduced body weight gains observed inad libitumfed rats, and reduced intake of saccharin and ethanol. Compared to controls, there was a significant reduction in HFS-induced long-term depression (LTD) in rats exposed to either drug alone, and an absence of LTD in rats exposed to the drug combination. Bath application of indiplon or AR-A014418, which enhance GABAAreceptor function or inhibit glycogen synthase kinase 3β (GSK3β), respectively, suggested the effects of ethanol, THC or their combination were due in part to lasting adaptations in GABA and GSK3β signaling. These results suggest the potential for long-lasting adaptations in mPFC output following co-exposure to alcohol and THC.

Combined use of cannabis and alcohol is common in adolescents. However, the extent to which such polydrug exposure affects the brain and behaviors remains under-investigated in preclinical studies. This study tested the hypothesis that combined exposure of Δ-9-tetrahydrocannabinol (THC), the main psychoactive constituent of cannabis, and alcohol will have additive effects on cognitive impairments and altered endocannabinoid levels in the hippocampus and frontal cortex. Male Long Evans rats were provided with daily access to cookies laced with oil or dronabinol, a synthetic THC, during adolescence. Three days after discontinuation of edible THC, the effect of orally administered 3 g/kg alcohol on Barnes maze performance was assessed. The results showed that experience with edible THC facilitated the occurrence of increased moving speed on the maze induced by repeated alcohol administration. However, contrasting to the hypothesis, the combined THC and alcohol exposure did not lead to additive deficits in learning and memory on the Barnes maze. While little effect on endocannabinoid levels was observed in the hippocampus, acute abstinence from alcohol significantly reduced endocannabinoid levels in the frontal cortex. In particular, reduction of N-oleoyl ethanolamine (OEA) and N-stearoyl ethanolamine (SEA) were robust and had an interactive effect with discontinuation from edible THC. These findings add to the scarce literature on THC and alcohol associated changes in endocannabinoid levels and provide insights to future investigations on the roles of OEA and SEA on physiology and behaviors following THC and alcohol co-exposure during adolescence.

Whereas co-use of alcohol and marijuana is prevalent in adolescents, the effects of such drug co-exposure on ingestive and cognitive behaviors remain largely unexplored. We hypothesized that co-exposure to alcohol and ∆9-tetrahydrocannabinol (THC), the main psychoactive constitute of marijuana, alters feeding behavior and cognition differently from either drug alone.Male rats received daily THC (3-20 mg/kg/day) or oil vehicle through subcutaneous injection or consumption of a cookie with access to saccharin or saccharin-sweetened alcohol during adolescence (P30-45). Barnes maze and sucrose preference tests were applied to assess spatial memory and behavioral flexibility and abstinence-related anhedonia, respectively.Subcutaneous THC did not affect alcohol intake but dose-dependently increased acute (3 h) chow intake and reduced weight gain. Moderate alcohol consumption reduced the acute hyperphagic effect of subcutaneous THC. By contrast, oral THC at a dose > 5 mg/kg robustly reduced alcohol intake without affecting 3-h chow intake. At this dose, some rats stopped consuming the THC-laced cookies. Furthermore, oral THC reduced weight gain, and co-exposure to alcohol alleviated this effect. Chronic subcutaneous, but not oral, THC reduced sucrose intake during abstinence. Neither treatment impaired cognitive behaviors in the Barnes maze.Moderate alcohol and THC consumption can interact to elicit unique outcomes on ingestive behaviors and energy balance. Importantly, this study established a novel model of voluntary alcohol and THC consumption for studying mechanisms underlying the consequences of adolescent onset co-use of the two drugs.