Catecholamines, derived from the amino acid tyrosine, produced by
the adrenal glands, which are found on top of the kidneys. are
epinephrine (adrenaline), norepinephrine (noradrenaline) and dopamine.
The hormone are released into the blood during times of physical or
emotional stress.
Dopamine
1. Acetylcholine-dopamine and CNS disorders
The substantia nigra pars compacta and ventral tegmental area of
midbrain dopaminergic nuclei and their respective forebrain and cortical
target areas are well established as serving a critical role in
mediating voluntary motor control, as evidenced in Parkinson's disease,
and incentive-motivated behaviors and cognitive functions, as exhibited
in drug addiction and schizophrenia, respectively. According to the
study by The University of Memphis, acetylcholine may be as important in
regulating dopaminergic transmission. Midbrain dopaminergic cell tonic
and phasic activity is closely dependent upon projections from hindbrain
pedunculopontine and the laterodorsal tegmental nuclei, which comprises
the only known cholinergic inputs to these neurons(1). Other study
indicated that combinatorial signaling through dopamine and serotonin (DA and 5-HT) receptors can regulate the brain region- and cell-type specific pMeCP2 in the CNS(1a).
2. The effects of Dopamine and dobutamine on heart rate
In the study of twenty patients with symptomatic CHF (systolic
dysfunction) were enrolled. After recording one-hour baseline
electrocardiographs (ECGs), patients were randomly selected for either dopamine
(4 micrograms/kg/minute, Group A) or dobutamine (4
micrograms/kg/minute, Group B) treatment for three days, conducted by
Taichung Veterans General Hospital, found that Dopamine and dobutamine have comparable therapeutic effects in patients with CHF, but low-dose dopamine more favorably affects cardiac autonomic function(2).
3. Dopamine and blood pressure and cerebral hemodynamics
In a Standard meta-analytic techniques, including random and fixed
effects models used to calculate combined effect size correlations and
significance levels showed that Dopamine administration increases mean and systolic blood pressure in hypotensive preterm infants, and is more effective than dobutamine, colloid or hydrocortisone alone. Dopamine
administration is associated with increased CBF, with greater increases
in CBF in hypotensive than in normotensive preterm infants. Dopamine is not associated with a greater incidence of adverse effects than other therapies used to treat hypotension(3).
4. Dopamine in schizophrenia and Parkinson's disease
The neurotransmitter dopamine (DA) and the dopaminergic neurones play an important role in schizophrenia and Parkinson's disease
(PD). According to the study byUniversity of Southampton, Royal South
Hants Hospital, A decrease in DA in the substantia nigra of the brain
has been implicated as the cause of PD. By contrast, it is argued that a
functional excess of DA or oversensitivity of certain DA receptors is
one of the causal factors in schizophrenia(4).
5. Dopamine and Attention deficit hyperactivity disorder
Through neuromodulatory influences over fronto-striato-cerebellar circuits, dopamine and noradrenaline play important roles in high-level executive functions often reported to be impaired in attention-deficit/hyperactivity disorder
(ADHD). According to the study by University of Cambridge, Cambridge,
United Kingdom, Medications used in the treatment of ADHD (including
methylphenidate, dextroamphetamine and atomoxetine) act to increase
brain catecholamine levels. However, the precise prefrontal cortical and
subcortical mechanisms by which these agents exert their therapeutic
effects remain to be fully specified(5).
6. Dopamine and restless legs syndrome
Restless legs syndrome
(RLS) is a common neurological disorder causing considerable impairment
to daily living. In a study to assess the reporting quality of
published RCTs according to the Consolidated Standards of Reporting
Trials (CONSORT) statement and to synthesize the study results in terms
of efficacy and tolerability to inform the clinical management of RLS,
showed that
DAs were significantly more efficacious in the treatment of RLS compared with placebo(6).
7. Dopamine receptors and cognitive and motor function
According to the study by, Columbia University
College of Physicians & Surgeons, repeated administration of this
methamphetamine (5 mg/kg administered three times at 2-h intervals)
leads to a transition from horizontal hyperlocomotion to excessive
orofacial stereotypy (taffy pulling) only in wild type and D3 mutants.
In both genotypes, this transition is accompanied by a change in the
relative ratios of striatal neuronal activation in two neurochemically
distinct compartments, with striosomal neuronal activation exceeding
that of the striatal matrix during stereotypy. Both the stereotypic
response to METH and the associated predominant activation of neurons
located in striosomes require D2-receptor expression. These studies
indicate a differential requirement for D1- and D2-like receptor
activation in mediating the effects of METH on cognitive and motor
function(7). Other indicated that the 'D3 Dopamine
Receptor Hypothesis' suggests D3 antagonists could prevent
sensitization, and may interrupt the development of psychosis when
administered during the prodromal phase of psychotic illness(7a).
8. Dopaminergic neurotransmission and behavioral changes
Dehydration is a powerful stimulus causing
disequilibrium in homeostasis of water and electrolytes resulting from
depletion in total body water. In the study of desert animals allows
improved understanding about water balance and resistance to dehydration
and associated behavioral changes, including those related to voluntary
movements, showed that dehydration is able to increase dopaminergic
neurotransmission, which might be involved in generating hyperactivity
in this desert animal(8).
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Sources
(1) http://www.ncbi.nlm.nih.gov/pubmed/20370804
(1a) http://www.ncbi.nlm.nih.gov/pubmed/21956448
(2) http://www.ncbi.nlm.nih.gov/pubmed/9614778
(3) http://www.ncbi.nlm.nih.gov/pubmed/21273985
(4) http://www.ncbi.nlm.nih.gov/pubmed/9849144
(5) http://www.ncbi.nlm.nih.gov/pubmed/21550021
(6) http://www.ncbi.nlm.nih.gov/pubmed/20206780
(7) http://www.ncbi.nlm.nih.gov/pubmed/15542707
(7a) http://www.ncbi.nlm.nih.gov/pubmed/11566480
(8) http://www.ncbi.nlm.nih.gov/pubmed/22847013
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