 Dear students, in this topic we shall discuss the phenomena of neuro modulation. Neuro modulation is a physiological process in which a neurotransmitter released by a group of neurons diffuses through a large area affecting large areas of central nervous system where these neurotransmitters interact and modulate the effect of many neurons simultaneously. This phenomena is different from normal neurotransmissions that a pre-synaptic cell which releases a neurotransmitter affects only one post-synaptic cell. But here a neurotransmitter which is released by a neuron or a few neurons spreads and affects the cells of all the areas of the brain. Such substances or such neurotransmitters which are involved in altering the cellular properties and efficacy of synaptic transmission of multiple neurons are called neuro modulators. The neuro modulators act through G-protein linked receptors and use voltage-gated ion channels for ion movements. Incarispons slow indirect neurotransmission mechanism. Major neuro modulators produced in the central nervous system include dopamine, serotonin, acetylcholine, histamine, norepinephrine, endorphins, enkaphalins or substance P-chamel. Now we shall discuss the basis of neuro modulatory action. A neuro modulatory agent is secreted or released as a neurotransmitter. But after its release in the synaptic cleft it is not deactivated, it is not reabsorbed and it is not broken down into its metabolites. As a result it remains available for stimulation for a longer time. As a result it influences or modulates the activity of several other neurons. Now we shall discuss the mechanism of action of neuro modulators. Neuromodulators do not act by producing excitatory or inhibitory post-synaptic potentials. Rather they produce long-term changes that slightly modify or depress or enhance the action of neurotransmitters at the synapses. The neuro modulators may act as autocrine or paracrine agents. As autocrine agents they rebind to the cell that produce them, that is the presynaptic cell and direct it to release or inhibit the release of further neurotransmitters. The cell that produced them acts on the same cell and directs it to produce more neurotransmitters or not produce more neurotransmitters. This is called modulation. As paracrine agents they do not act on the cell that produced them but act on the other cells of the brain and control their release mechanisms or affect them. This way the amount of neurotransmitters that are released affects them. Here students now we shall discuss the effects of neuro modulation. Neuromodulation is involved in the development of complex behavioral patterns. For example, happiness, exploration, tajasus, revenge, hussa, badla, reward and greed. These kinds of feelings and behaviors are the effects of neuro modulation. Similarly, processes of thinking, cognition, thought, understanding, planning, learning and memory. They actually involve a large number of cells that work on the same pattern and produce these complex behaviors and play a role for these neuro modulators. But in addition to these normal phenomena, many behavioral problems, neuro modulatory actions may produce disturbances or imbalances. For example, mood swings, sleep disturbances, feelings of stress, anxiety, anger and depression due to these problems. Neuromodulators have been used in pharmacological, i.e. they are used as medicine. Many pharmacological actions or pharmacological uses are used for challenging nervous diseases. For example, ADHD, attention deficit, hyperactivity, disorder. Then another challenging disease is narcolepsy, which causes the problem of sleep cycles. Epilepsy, depression, dementia, Alzheimer's disease, memory loss in old age and Parkinson's disease. These neuro modulatory effects are produced and neuro modulators are used as pharmacological drugs.