Endorphins are opiate-like chemicals that produce feelings of euphoria and calmness in response to external stimuli like excitement, pain, and exertion. They are produced in the brain and decrease anxiety and stress whilst promoting well-being and relaxation. There is speculation and some biochemical evidence to suggest that genuinely high energy or high anxiety dogs have a lower than normal level of these opiate compounds, or that they do not produce them as efficiently as others that present as more low energy. It could equally be the case that they produce a 'normal' amount of endorphins but due to their high energy (and as a consequence an often frustrating and boring life) this is not enough when looked at in the context of their need for stimulating activity.
Whatever the reason, be it because they are high energy therefore they require more than the 'normal' amount of endorphin production, or whether individuals that produce lower levels of endorphins are by nature more 'hyperactive' as a result, the fact remains that there is a link between the two. Serotonin should be mentioned briefly here too as this is the chemical that affects mood, sleep patterns and appetite.
Where endorphin levels are too low to accommodate the dogs lifestyle (or the lifestyle is too sedate to accommodate the dogs low endorphin production...) the dog is likely to feel under a lot of emotional stress, this can result in neurotic behaviour, paw chewing/self harm and other obsessive behaviours that the dog uses to cope. Anything that induces pain or excitement boosts endorphin levels - so a dog could lick his paw raw as a coping mechanism, or chase shadows, or bark excessively at the window all day long, this becomes their way of 'self medicating' as it boosts the endorphin production in the brain which fills the deficit between their lifestyle and their brain chemistry. This kind of stress can also result in skin problems due to increased blood levels of cortisol disrupting normal functioning of the immune system, depleting it's efficiency and leaving the dog open to an over-blown reaction to normal irritants and bacteria which can cause an allergic response.
The brain chemistry of dogs is fascinating and very complex - we don't know anywhere near everything there is to know about the dogs brain - but luckily we do know how to boost endorphin and serotonin levels in our dogs, and also how to reduce stress in order that the endorphin requirements are reduced.
Exercise is a fantastic way to boost serotonin and endorphin production. A good run and lots of walking will not only drain excess energy in the dog, but will aid in the production of both endorphins and serotonin which will help your anxious or high energy dog to feel calm, relaxed and sleepy. It is now known that although endorphin levels in the blood do increase with exercise, they do not cross the blood-brain barrier and effect mood - as previously thought. The brain only produces elevated levels of endorphins where fatigue, high excitement, pain or physical discomfort are present, so unless you were to take your dog long distance running with you and push his limits every single day, exercise is not going to improve endorphin production in the brain long term. Your dog will however develop an even mood when exercised properly due to blood endorphin levels being elevated for a time, spent energy, access to sunlight and by having his interest engaged.
Diet and nutrition are definitely factors when looking at endorphin and serotonin production in a very high energy dog, the fuel that your dog takes in affects cognition and mood, it also contains varying levels of the serotonin precursor tryptophan which is essential for serotonin production. This can be found in dairy and turkey and in many other high protein foods, however high protein diets - although rich in tryptophan - do not allow sufficient tryptophan to cross to the brain due to high competition with five other amino acids found in protein, so a lower protein diet and perhaps a supplement in addition is recommended. This could prove helpful where anxiety, inability to sleep/settle are factors.
Conversely raw feeding based around poultry and fish can be beneficial despite the elevated protein so some trial and error may be necessary to find the best course of action for a particular dog, raw is particularly beneficial for those dogs with access to plenty of exercise and those that show a lack of appetite.
Another important factor to consider is sunlight. Sunlight affects mood and aids rest through allowing for the production of Serotonin and Melatonin. Melatonin is the hormone that helps the dog to feel sleepy, it encourages our dogs to fall asleep in the first place and controls the circadian rhythm. Sunlight also provides vitamin D which is needed for strong immune function (this is a factor where the dog is under stress - stress and anxiety can deplete the immune system sometimes quite dramatically).
Not only can we boost the levels of beneficial chemicals in the brain and body but we can also try to reduce the stress that the dog is under in order to bring the requirement of higher levels of endorphins down.
Challenging the dog mentally and physically can enable him to cope with lower than average levels of endorphin production. Most very high energy dogs would benefit from some intellectual stimulation. It is often the case that these very anxious and/or active dogs need a job to do, a purpose. A lot of energy can be expended learning tricks or helping around the house fetching and carrying things etc. The more the brain can be engaged in learning and carrying out new behaviours the more satisfied and relaxed the dog will be. This also improves self esteem hugely in nervous individuals. In very active individuals teaching waiting type activities can help the dog learn some impulse control, this is very challenging for the hyperactive dog and will tire him out surprisingly quickly as well as slowing him down somewhat. If in doubt I would look to the breed for clues on how to fulfil the dogs energy expulsion requirements.
Apart from exercise, diet, intellectual stimulation and sunlight, a good solid routine can also reduce the amount of stress that a high energy dog is under. Routine is brilliant, it allows the dog a predictable day that is 'broken up' into different activities. For example if the dog rests at the same time every day then he quickly learns when to voluntarily choose to calm himself enough to carry this out. Chewing has a calming effect on the brain so chewable items should always be available to the genuinely high energy/anxiety dog, this is an excellent way to self-calm in a healthy way.
And last but not least, (all together now...) be sure that the dog sees the owner as in control! A dog will always feel more stressed if he feels that he is responsible for the care and protection of the family, so although this advice has been thrown out by many it still remains an important factor for dogs like this, kind consistency and sensible rules offer structure, work the mind and in turn promote relaxation.