Info

The Parkinson's-Reversing Breakthrough

Is There A Cure for Parkinson Disease

Get Instant Access

Figure 4.5 There are currently five types of dopamine receptor identified in the human nervous system, Di to D5. Di and D5 receptors are similar in that they both stimulate the formation of cAMP by activation of a stimulatory G-coupled protein. D1 and D5 are therefore known as D1-like receptors. D2 to D4 receptors activate an inhibitory G-protein, thereby inhibiting the formation of cAMP. They are collectively known as D2-like receptors. D2 receptors are more ubiquitous than D3 or D4 receptors. D3 receptors are differentially situated in the nucleus accumbens (one of the septal nuclei in the limbic system) and D4 receptors are especially concentrated in the frontal cortex

Caudate-putamen N. accumbens Olfactory tubercule

Hippocampus Hypothalamus

Caudate-putamen N. accumbens Olfactory tubercule

Olfactory tubercule Hypothalamus N. accumbens Cerebellum

Frontal cortex Medulla Midbrain

Caudate-putamen N. accumbens Olfactory tubercule

Hippocampus Hypothalamus

Caudate-putamen N. accumbens Olfactory tubercule

Olfactory tubercule Hypothalamus N. accumbens Cerebellum

Frontal cortex Medulla Midbrain most of the newer antipsychotics, may be protective against EPS by altering this threshold (reviewed in reference 10).

Recent neurochemical imaging studies have indicated that people with schizophrenia have an increased sensitivity of their dopaminergic neurones to amphetamine challenge11 (Figure 4.4). Thus, it may be that in response to 'stress' such people will over-release dopamine and this may drive psychosis.

There are currently five types of dopamine receptors identified in the human nervous system: Di to D5. Di and D5 receptors are similar in that they both stimulate the formation of cAMP by activation of a stimulatory G-coupled protein. D2 to D4 receptors act by activating an inhibitory G-protein, thereby inhibiting the formation of cAMP. D2 receptors are more ubiquitous than D3 or D4 receptors. D3 receptors are differentially situated in the nucleus accumbens (one of the septal nuclei in the limbic system) and D4 receptors are especially concentrated in the frontal cortex (Figure 4.5). There are a number of different dopaminergic pathways or tracts (Figure 4.6). The nigrostriatal tract projects from the substantia nigra in the midbrain to the corpus striatum. This tract primarily has a role in motor control, although the ventral striatum has a role in reward- and goal-directed behaviors. Degeneration of the cells in the substantia nigra leads to idiopathic Parkinson's disease, and it is by blocking the dopamine receptor at the termination of this pathway that the parkinsonian side-effects of classical antipsychotics arise. The mesolimbic/ mesocortical tract has its cell bodies in the ventral tegmental area adjacent to the substantia nigra. This tract projects to the limbic system and neocortex in addition to the striatum. This

Was this article helpful?

0 0

Post a comment