Ethanol impairs memory by reducing the synaptic connection of the hippocampal spatial neurons

Document Type: Research Paper

Authors

Department of Biology, Faculty of Basic Sciences, Shahed University, Tehran, Iran

10.22070/jbcp.2020.5249.1129

Abstract

Background and Objective: Ethanol has undesirable effects on memory and synaptic communication. However, its impact on the learned spatial memory is unclear. We investigated the damaging effects of ethanol on place neurons of rat’s hippocampal CA1.
Materials and Methods: Sixty four male Wistar rats (250 g) were administered high (1-8 g/kg) or low (0.05-0.1 g/kg) doses of ethanol intraperitoneally (i.p.) and tested (10 min) for the novelty-seeking behavior using the place conditioning box. Sniffing, rearing, grooming, and compartment entering was compared between the first and the last stage, during which the animals had accessibility to the whole device. During the acquisition phase, the rats daily received ethanol (i.p.) and confined in one side of the device for 40 min. The control group solely received saline (1 ml/kg, i.p.). The achievements were analyzed by ANOVA under α = 0.05.
Results: The ethanol-acquired animals with the high doses did not recall the information of the familiarization day and displayed a high tendency toward the non-confined side of the box. The rats also showed a reduction in place neuron synaptic strands.
Conclusion: Ethanol disrupts spatial memory and also diminishes CA1 place neuron’s fibers.

Keywords


  1. Tolman EC. Cognitive maps in rats and men. Psychological Review 1948; 55: 189-208.
  2. O’Keefe J, Nadel L. The Hippocampus as a Cognitive Map. Oxford University Press, Walton Street, Oxford OX2 6DP 1978.
  3. Okada K, Okaichi H. Functional differentiation and cooperation among the hippocampal subregions in rats to effect spatial memory processes. Behavioural Brain Research 2009; 200(1): 181-191.
  4. Gallistel CR. The organization of learning. Cambridge, MA: Bradford Books, MIT Press 1990.
  5. Wills TJ, Cacucci F, Burgess N, O'Keefe J. Development of the hippocampal cognitive map in preweanling rats. Science 2010; 328 (5985):1573-1576.
  6. Eichenbaum H. The role of the hippocampus in navigation is memory. Journal of Neurophysiology  2017; 117:1785-1796.
  7. Tianna R, Hicklin PH, Wu RA, Radcliffe RK, Freund SM, Goebel-Goody PR. Alcohol inhibition of the NMDA receptor function long-term potentiation, and fear learning requires striatal-enriched protein tyrosine phosphatase. Proceedings of the National Academy of Sciences 2011; 108(16): 6650-6655.
  8. Rezayof A, Shirazi-Zand Z, Zarrindast MR, Nayer-Nouri T. Nicotine improves ethanol-induced memory impairment: The role of dorsal hippocampal NMDA receptors. Life Sciences 2010; 86: 260-266.
  9. Tveden-Nyborg P, Bergmann TK, Lykkesfeldt J. Basic & Clinical Pharmacology & Toxicology Policy for Experimental and Clinical studies. Basic & Clinical Pharmacology & Toxicology 2018; 123: 233-235.
  10. White AM, Matthews DB, Best PJ. Ethanol, memory, and hippocampal function: a review of recent findings. Hippocampus 2000; 10(1): 88-93.
  11. Woolf NJ. Cholinergic systems in mammalian brain and spinal cord. Progress in Neurobiology 1991; 37: 475–524.
  12. Robbins TW, Ersche KD, Everitt BJ. Drug addiction and the memory systems of the brain. Annals of the New York Academy of Sciences 2008; 1141: 1–21.
  13. Garthwaite J, Boulton CL. Nitric oxide signaling in the nervous system. Annual Review of Physiology 1995; 57: 683-706.
  14. Qiang M, Chen YC, Wang R, Wu FM, Qiao JT. Nitric oxide is involved in the formation of learning and memory in rats: studies using passive avoidance response and Morris water maze task. Behavioural Pharmacology 1997; 8(2-3): 183-187.
  15. Tizabi Y, Bai L, Copeland RL Jr, Taylor RE. Combined effects of systemic alcohol and nicotine on dopamine release in the nucleus accumbens shell. Alcohol 2007; 42: 413–416.
  16. Taber K, Black D, Porrino L, Hurley RA. Neuroanatomy of Dopamine: Reward and Addiction. Journal of Neuropsychiatry and Clinical Neurosciences 2012; 24(1): 1-4.
  17. Shomrat T, Levin M. An automated training paradigm reveals long-term memory in planarians and its persistence through head regeneration. Journal of Experimental Biology 2013; 216: 3799-3810.
  18. Varela C, Weiss S, Meyer R, Halassa M, Biedenkapp J, Wilson MA. Tracking the time-dependent role of the hippocampus in memory recall using DREADDs. PLoS One 2016; 11(5): e0154374.
  19. Mercer T, Jones GA. Time-dependent forgetting and retrieval practice effects in detailed visual long-term memory. Quarterly Journal of Experimental Psychology 2019;72(6):1561-1577.
  20. Spanagel R. Alcoholism: a systems approach from molecular physiology to addictive behavior. Physiological Reviews 2009; 89: 649–705.