Reduction in central_____ plays a vital role in suicidal behavior.

Ans. c (Serotonin) (Ref. Harrison's medicine 17th ed., 2717; Kaplan & Sadock's Synopsis of Psychiatry, 10th ed., p. 901)Biological Factors in Suicide# Diminished central serotonin plays a role in suicidal behavior.# Low concentrations of CSF 5-HIAA also predicts future suicidal behavior.ETIOLOGY AND PATHOPHYSIOLOGY OF SUICIDE# There is some evidence that a functional polymorphism in the serotonin transporter (5-HTT) gene may interact with stressful life events to markedly increase risk of depression and suicide.# Postmortem examination of brains of suicide victims indicate altered noradrenergic activity, including increased binding to a1, - a2-, and b-adrenergic receptors in the cerebral cortex and decreased numbers of noradrenergic neurons in the locus coeruleus. Involvement of the serotonin system is suggested by findings of reduced plasma tryptophan levels, a decreased cerebrospinal fluid level of 5-hydroxyindolacetic acid (the principal metabolite of serotonin in brain), and decreased platelet serotonergic transporter binding. An increase in brain serotonin receptors in suicide victims and decreased expression of the cyclic AMP response element-binding (CREB) protein are also reported.# However, a decrement in mood after tryptophan reduction is considerably less robust in untreated patients, indicating that, if presynaptic serotonergic dysfunction occurs in depression, it likely plays a contributing rather than a causal role.DiseaseAssociated Change in NeuotransmitterSucidal behavior>|?HIAA and serotoninAnxiety| NE, GABA, |serotonin (5HT).DepressionNE and | serotonin (5HT).Alzheimer's dementia|ACh.Huntington's disease|GABA, |ACh.Schizophrenia| dopamine.Parkinson's disease|dopamine, | ACh.Educational point:NTCell BodiesTerminal locationNotesGlutamateGABACortexStriatumSpinal CordInter-neurons,Spinal CordAMPA (Na), NMDA (Ca), Ketamine, Stroke/ lschemiaAnticonvulsantsBarbiturateBenzodiazepineAnestheticsEtOHAchNucleus Basalis, SeptumCortex, HabenulaMemoryAlzheimer'sMyasthenia gravisDopamineSubstantia Nigra, VTACaudatePutamen, Limbic,Frontal Cortex,PituitaryParkinson'sDrug craving Psychosis| ProlactinNELocus CoeruleusCortex Limbic-5-HTRaphe nucleiForebrainLow levels in suicidal behavior.Acts as inhibitor of pain pathways in the cord.Sleep.Acts an inhibitor in higher regions of CNS is believed to help control the mood.MigraineAnti-anxiety.Anti-psychosis.Anti-emetic.Opioid peptidesHypothalamusBasal gangliaPituitaryHypothalamusEndorphinEnkephalinDynorphin