Elsevier

Legal Medicine

Volume 51, July 2021, 101875
Legal Medicine

Neural dysfunctions following experimental permanent occlusions of bilateral common carotid arteries cause an increase of rat voluntary alcohol drinking behavior

https://doi.org/10.1016/j.legalmed.2021.101875Get rights and content

Highlights

  • Voluntary alcohol drinking behavior was increased in the rats treated with the permanent two vessel occlusion.

  • Alcohol perfusion-induce dopamine and serotonin releases in the nucleus accumbens of the permanent two vessel occlusion-treated rats were significantly suppressed.

  • The contents of dopamine decreased in the nucleus accumbens, caudate-putamen, ventral tegmental area and lateral hypothalamus.

Abstract

We have previously reported that ischemic animal models treated with a respiratory inhibitor, rotenon, show an increased voluntary alcohol intake. Although it is clear that ischemic brain, as a result of reduced-blood flow, shows pathological events and/or neuro-degenerations apparently, little is known of causal relationship between the mechanism of neural dysfunction and voluntary alcohol consumption. Authors have investigated effects of permanent two-vessel occlusion (p2VO) on rat voluntary alcohol drinking behavior. In first experiment the p2VO-treated rats showed an increase of voluntary alcohol drinking behavior, as compared with sham controls. Using brain microdialysis technique, increases of only nucleus accumbens (ACC) dopamine (DA) releases were suppressed in the p2VO-treated rats significantly, following the high K+ (40 mM) perfusion through the microdialysis probe membrane. Alcohol (200 mM) perfusion-induced DA and serotonin (5-HT) releases in the ACC of the p2VO-treated rats were suppressed significantly in the second experiment, as compared with the sham-treated rats. In third experiment p2VO-treated rats showed significant decreases of the contents of DA, not 5-HT, in the ACC, caudate-putamen (C/P), ventral tegmental area-substantia nigra (VT/SN) and lateral hypothalamus (LH). Dopaminergic neurons in the ACC showed more functional vulnerability against the p2VO treatments, as compared with the serotonergic neurons. An increase of alcohol intake in the p2VO-treated rats means the compensation for the neural degeneration of the dopaminergic system in the ACC consisted brain rewarding system. It was likely suggested that neural disturbance of higher functions involved with incomplete global brain ischemia leads the risk of an abnormal alcohol drinking in human.

Introduction

Brain injury by transient complete global brain ischemia (cardiac arrest or heart failure) and regional incomplete brain ischemia (ischemic stroke) afflicts many patients with death or serious, long-term and permanent disability in the world. In 2015, 156.5 to 100,000 people in Japan have suffered from heart failure or stroke [1].

A functions of central neurons cannot regenerate, when they are damaged with severe ischemic stroke which causes neural death. Ischemic stroke in the brain is a major cause of lasting functional damage, memory disturbance, headache and dissing in humans [2]. A hypothesis has been reported, such as an increase in calcium (Ca2+) influx caused by activation of NMDA receptor [3] and massive increase of DA and 5-HT neurotransmitter releases in the brain [4].

Ischemia is believed to be caused by neuronal damage because the brain is dependent on a continuous supply of glucose and oxygen that is regulated by cerebral blood flow. A damaged brain, as a result of reduced blood flow, shows complex pathological and functional events [5]. In animal models, global and transient cerebral ischemia, mostly due to cardiac arrest, induced the loss of brain function, and usually the normothermic brain cannot be revived after 8–10 min of ischemia [6]. However, the function of the hypothalamic pituitary system related with energy homeostasis of the vital signs was observed for some period after brain death and nerve cell damages, especially those in the hypothalamic area, have resistance to anoxia and stasis of the blood stream [7]. Global and transit cerebral ischemia, which is mostly due to cardiac arrest in human, induces disturbances of emotion and consciousness as high neuronal functions, dizziness, and headache [8]. Nervous disturbance might affect their human lifestyle involved with eating and alcohol drinking.

Several lifestyles involved with alcohol drinking patterns were well not known in ischemic stroke survivor and its patients. Alcohol drinking behavior in human and animal models is correlated with complex interactions among biomedical, physiological and social aspects, especially neural function of brain rewarding system. Main risks of alcoholism depend on interactions between genetic, environmental and neurobiological factors. The precise nature of these factors is still unknown. Although serotonin (5-HT) and dopamine (DA) have been suggested to have role in alcohol drinking behavior, studies have yielded inconsistent with findings involved with the releases of these two neurotransmitters depending on specific brain area or brain nucleus [9]. Changes in alcohol drinking behavior have been observed in adult rats treated with respiratory inhibitor rotenone [10], and dopaminergic neurotoxin, 6-OHDA, and serotonergic neurotoxin, 5,7-DHT [11], [12], although the underlying mechanism remains underspecified.

It is now hypothesized that effects of long-term exposure of alcohol or increased alcohol intake are due to neuroadaptation as well as neurotoxicity [9], [13]. These findings suggested that dopaminergic systems are associated with alcohol drinking behavior in rats with neural degeneration, but neural adaptations were not well understood demonstrated yet.

In the present study, to test the causal relationship between the release of neurotransmitters as the index of the neuronal dysfunctions and alcohol drinking behaviors using a newly developed reversed brain microdialysis technique [14], [15], we examined the neuronal reversibility concerning the release of dopamine (DA) and serotonin (5-HT) in the nucleus accumbens (ACC), which consists of the brain basal ganglia and plays an important role in the reinforcement or drug abuse [11], [12] after the treatment of bilateral carotid arteries occlusions. The performance of this test will be a good criterion to assess the potential neuroprotective manner in brain anoxia patients.

Section snippets

Animals

Male Wistar rats (4–5 months old, Japan CLEA, Osaka, Japan) were used. The animals were housed in groups of 2–3 per cage, and the housing condition was maintained at 23 ± 1℃ and 55 ± 5% relative humidity, with a 12-h light / dark cycle (lights on 07:00 – 19:00 h). Food and water were given ad libitum. All procedures were conducted in strict adherence to the Care and Use Guidelines of the Committee of Laboratory Animals in accordance with the ‘National Institutes of Health Guide for the Care and

Alcohol drinking behavior

In 4 h-time access alcohol drinking test, the p2VO-treated rats showed an increase in consumption of 10% alcohol solution on the time course (Time: F(3, 48) = 15.84, p < 0.0001; Treatment: F(1, 48) = 7.247, p < 0.01; Time × Treatment: n.s.)(Fig. 1A). The p2VO-treated rats also increased alcohol consumption significantly in the 4hr-time access (Fig. 1B).

Voluntary alcohol drinking behavior test, water (ml/day), 10% EtOH consumption (ml/day), daily EtOH intake (g/kg/day) and alcohol preference (%)

Discussion

Permanent bilateral carotid arteries occlusion (p2VO) shows several neurological infarctions, because each cerebral hemisphere is supplied by an internal carotid artery. These internal carotid artery and middle cerebral artery arise from the common carotid artery. The large surface branches of the middle cerebral artery supplies blood with the cerebral cortex and various subcortical structure, notably the caudate putamen, involved in the processing of sensor sensorimotor infarction [20], [21].

Conclusion

Voluntary alcohol drinking behavior increased significantly in the p2VO-treated rats. P2VO caused suppressions of alcohol-induced DA and 5-HT releases in the ACC, and decreased levels of DA in the ACC and C/P consisted of the brain rewarding system. Dopaminergic neurons were more vulnerable for the p2VO treatment than serotonergic neurons. Increased alcohol drinking behavior means compensation with the neural dysfunctions of the dopaminergic system of the survival neurons in the ACC of rat

Ethical Standard

The authors declare that the experimental project complies with the current laws of the countries in which they were performed.

Funding

The present study was supported by Grants-in-Aid for Scientific Research from the Ministry of Education, Science, Sports and Culture of Japan, JSPS KAKENHI Grant Numbers, 12670401, 15590584 and 2430176.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

The authors thank Emeritus Professors, Setuso Komura and Masahiro Yasuhara, Department of Forensic Medicine, Kyoto Prefectural University of Medicine, Graduate School of Medicine, for the excellent comments, directions and suggestions.

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