True that should be the answer
        
                    
             
        
        
        
Induced depression of single neurons in brain areas with opiate receptors
- Enkephalin, applied microiontophoretically, depressed spontaneous and glutamate-induced firing of  one neuron in frontal cortex, caudate nucleus, and periaqueductal gray matter, where enkephalin and high concentrations of opiate receptors are met.
- More than one depressions were blocked by the specific narcotic antagonist naloxone. The results  are durable with a neurotransmitter or neuromodulator role for this new brain pentapeptide.
- Opium derivatives have been in medical use for the last  2000 years, and may be   longer than any other class of drugs
- . The brain regions which was  involved in these actions have been identified in some instances by local microinjection of pmole quantities of opioids.
To know more about neurons    visit : brainly.com/question/24217914
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Answer:
Blood Brain Barrier(BBB)
Explanation:
This is a biological interface of special endothelial cells of astrocytes, pericytes , capillaries,  neurons and other  structures, acting as a physical barrier or  gate separating the Central Nervous system from the peripheral  blood circulations. Thus it  formed a tight junction serving as a  physical barrier to  selectively regulate the entrance of substances from the   cerebral blood flow   into the brain,  therefore maintaining homeostasis of the brain.
From above any  substances  absorbed into the blood stream  irrespective of the mode of entry  are transported through  the BBB, and  are selectively  regulated to enter the brain cells by the BBB's   interactions with the blood vessels, hormones etc. 
Basically it allows the passage of nutrients,  a few  drug, hormones and resists certain toxins and pathogens for the brain homeostasis.
 
        
             
        
        
        
Sunlight is transferred
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