Norepinephrine and dopamine are utilized in brain circuits which regulate all
body functions, mood, emotions, and cognitive abilities. These transmitters are
made from amino acids, supplied as proteins in foods or as free amino acids in
formulas such as Alpha ENF. Phenylalanine and tyrosine are first converted to
l-dopa, then dopamine, which can be converted to norepinephrine and epinephrine.
The oldest, most automatic and the most reliable systems in the brain control
all body functions and keep us alive. The term autonomic refers to the
autonomous function of these old systems that do not require consciousness or
learning and do not permit the intervention of the personal self. The dialectic
of approach avoidance is expressed in the two divisions of the autonomic nervous
system (ANS); the parasympathetic (PNS) network corresponds to eating, rest and
pleasure; the sympathetic system (SNS) corresponds to action, fight and flight.
Both systems are continuously active, but one system tends to dominate depending
on what is going on outside. THE ANS is an expression of norepinephrine acting
within the nervous system and as a hormone distributed in the blood to all
tissues, The ANS creates feelings in consciousness as a way of controlling our
activities. Emotions are strong programs that integrate the ANS with information
arising from cognitive processors. You may be quietly enjoying dinner with
friends until someone insults you. Within milliseconds, your SNS activates
flight and fight responses and you become angry. Your upset may last for hours
or days and you may never forgive the person who insulted you.
Some of the effects of SNS activation are: your pupils dilate, you sweat,
blood flow to muscles increases, your breathing and heart rate increases, your
blood pressure increases, digestive activity slows or stops. You become angry or
fearful, sometimes both. Drugs that stimulate the SNS are referred to as
The parasympathetic system uses acetylcholine
(not a catecholamine) as
the neurotransmitter and is found everywhere in the body. For example,
acetylcholine sends signals to muscle cells to contract. In the brain,
acetylcholine has arousal functions in the right amounts but tends to cause
depression in overdose. Alzheimer's disease is associated with declining levels
of acetylcholine and degeneration of neurons which use this neurotransmitter. PNS activity causes pupil constriction, increased
salivary gland secretions and digestive activity; heart and breathing rate
decreases as does blood pressure. You tend to feel relaxed. Drugs that stimulate
the PNS are referred to as parasympathomimetic agents. The two systems
collaborate on sexual activity, for example. Male erections are a SNS
responsibility and ejaculation is a PNS responsibility.
Norepinephrine is widely distributed in the brain and is the neurotransmitter
in neurons that determines consciousness, sleep rhythms, attention, and
vigilance. NE cell clusters within the brain's arousal complex (locus coeruleus)
organize sleep patterns. In rats, painful, uncontrollable electrical shocks
induce “depression” and are associated with early depletion of NE in the locus
of NE may lead to depression. Some antidepressants, especially imipramine,
selectively alter the synthesis of NE, but paradoxical experimental results tell
us that therapeutic changes are not achieved by just increasing one transmitter
but rather influencing the net arousal balance in the mesh of arousal circuits.
Imipramine, the grandmother of the family of tricyclic antidepressants, has
at least a triple action on NE, acetylcholine, and histamine circuits.
Imipramine's cousin, amitriptyline, works more on the serotonin neurons and also
has marked anti-acetylcholine activity. Both drugs are also good antihistamines.
The substrates of NE, phenylalanine, tyrosine, and l-dopa are not powerful
antidepressants, but they may have a contributing role in a well thought-out
neurochemical recipe. Stimulants, including caffeine, cocaine and amphetamines
act in a NE-increasing mode with temporary increase in psychic energy and a
sense of well-being. They also influence the dopamine system. Repeated use of these drugs leaves the over stimulated brain circuits in a
state of confusion, with disturbances of psychic energy, thinking, feeling, and
behaving. Withdrawal from these drugs is associated with other marked
Amphetamines act on NE receptors and will induce agitated, paranoid, and violent states in
susceptible people. As street drugs, amphetamines have major antisocial
consequences. Antidepressants of the MAO-inhibitor group (parnate, nardil)
increase norepinephrine levels but not serotonin. Withdrawal from these drugs is associated with other marked disturbances. Bromocritptine, a drug imitating the action of dopamine, is helpful in reducing
cocaine withdrawal symptoms. Antidepressants of the MAO-inhibitor group (parnate,
nardil) increase norepinephrine levels but not serotonin.