Substantia nigra depression

Firing rate of substantia nigra DA neurons increased Recovery from depressed firing rate of VTA DA neurons D 1-like antagonist in amygdala doesn t precipitate withdrawal Reduced amygdala central nucleus DA... 

Both clinical and experimental studies have provided evidence that 5-HT can also regulate dopamine turnover. Thus several investigators have shown that a positive correlation exists in depressed patients between the homovaniUic acid (HVA), a major metabolite of dopamine, and 5-HIAA concentrations in the CSF. In experimental studies, stimulation of the 5-HT cell bodies in the median raphe causes reduced firing of the substantia nigra where dopamine is the main neurotransmitter. There is thus convincing evidence that 5-HT plays an important role in modulating dopaminergic... 

Willner (1995) provides evidence from many sources that increases or decreases of dopaminergic activity in the mesolimbic system may underpin the pathophysiology of mania and depression respectively. A key area involved may be the subgenual prefrontal cortex which receives extensive reciprocal dopaminergic projections from the ventral tegmental area and substantia nigra and influences dopamine release in the nucleus accumbens (Drevets et al., 1997 see Chapter 16). 

Kokkinidis, Larry, Robert M. Zacharko, and Patrick A. Predy. 1980. "Post-Amphetamine Depression of Self-Stimulation Responding from the Substantia Nigra Reversal by Tricyclic Antidepressants." Plmmmcotogy Biochemistry and Behavior 13 379-83. 

Both the histamine neuron innervation and the density of H3 receptors are increased in the substantia nigra of Parkinsonian patients (Anichtchik et al. 2000 2001). The receptors probably are the H3 heteroreceptors on striato-nigral GABA terminals, and their increase may contribute to the depression of GABA release in the substantia nigra in Parkinson s disease (Garcia-Ramirez et al. 2004). 

The effects of THM on the central dopaminergic system were then examined (figure 6). TH activity was markedly depressed to 76, 56, and 21 percent of control in the striatum of rats administered a single ICV injection of 50, 100, or 200 g, respectively, of THM 5 days previously. A decrease in the content of DA and its metabolites in these structures was also observed. TH activity was not altered in the substantia nigra. Another metabolite of MDMA, 3,4-dihydroxyamphetamine (DHM), was administered ICV (135 g) and the enzymatic response was examined. 

GHB is short for gamma hydroxybutyrate. The form used as a club drug is a powerful, synthetically produced depressant that affects the central nervous system. However, GHB also exists naturally in the body. It is produced in the brain by a neurotransmitter called gamma-aminobutyric acid (GABA). GHB is found in several parts of the human brain, particularly the thalamus, the hypothalamus, and the substantia nigra. 

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