Greg Detre������������ Parkinson�s disease and schizophrenia 3^rd� February, 2000

Discuss the neurodegenerative changes in Parkinson�s disease and the way in which knowledge of these changes has guided the development of treatments.

What kinds of experiments have contributed to our knowledge of dopamine functions in the brain?

Notes: positive symptoms in shizophrenia

Notes: Chemical messengers in the brain

primary vs secondary

Notes: Anti-psychotic drugs

introduction

Parkinson�s disease and schizophrenia are sometimes seen as opposite sides of the same coin � the one can be seen as a long-term decline in the presence of dopamine and the dopaminergic pathways, while the latter seems to be linked with the dopamine receptors being over-stimulated.

Yet, radically different effects are observed, and in different areas of the population. Parkinson�s disease tends to strike in the elderly (approximately 1% of the elderly population suffer from it), seeming to cause a marked decline in levels ofo dopamine, with worsening effect on the motor system, especially the basal ganglia (why doesn't this only effect emotional involuntary movement?).

In contrast, the effects of schizophrenia consist of flattened affect and abnormal mental function. Although the disorder is not usually detected until it has become severe enough to require evaluation or treatment in a clinic or hospital, symptoms can be seen in the under-twenties.

have they considered giving L-DOPA to the elderly?

stastical deviance view � madness is only a case of the frequency and intensity of the symptoms, as naturally occuring patterns

others see the symptoms as being qualitatively different, a pathology � with mental/physical causes

whether illnesses in the sense of a distinguishable abnormality or deviances purely in terms of the degree of difference from the norm, psychopathologies cause considerable anguish + disability

parkinson�s disease

symptoms

causes

cures/progress

schizophrenia

types of schizophrenia

Schizophrenia is a term used to describe a group of serious disorders, affecting up to 1% of the population and accounting for about half the beds in mental health hospitals.

Progress in its study has been slow, for a number of reasons. In the first place, the term �schizophrenia� is used to categorise an extremely wide range of disorders, including disorders of cognition, emotion, behaviour and social integration.

This led to Crow�s two-process theory, which divides it into two fairly distinct pathologies of varying severity, variously known as Type I and Type II, or positive and negative. The positive form is characterised by the presence of hallucinations, delusions and thought-disorders. The negative form displays as poverty of speech, flattening of affect and social withdrawal (especially noticeable biologically by the enlargement of the brain ventricles and shrinking brain mass).

More recent studies enlarge on this distinction, further dividing the �positive� category into �psychotic� and �disorganised�. This distinction can be partly justifed in physiological terms. It seems increasingly likely that schizophrenia cannot be seen in just psychological terms as a purely cognitive dysfunction; rather, evidence from treatment and autopsies suggests biochemical and anatomical anomalies which correlate reasonably well with a tri-partite distinction.

�Classical� anti-psychotic treatments like Thorazine and Haldol have proven reasonably effective in a large number of cases by blocking the dopamine receptors in the brain. There is a strong correlation between the effectiveness of a drug in forming dopamine blockades and its effect on positive schizophrenics. Increased circulation of dopamine in neural circuits appears to lead to schizophrenics� inability to concentrate on certain stimuli, being continually distracted by the extraneous and being unable to maintain a steady train of thought (just as patients suffering from a lack of dopamine sometimes exhibit opposite symptoms: ignoring stimuli and less active cognitive functioning).

To see what happened, Davis injected a group of patients with mild schizophrenia with a drug with temporarily increases dopamine levels; it produced a startling increase in the floridity of the patients� symptoms.

Its etymology leads to confusion with �dissociative identity disorder�; however, schizophrenia is characterised instead by disorders of cognition, emotion, behaviour and social integration.

an �abnormal disintegration of mental functions� (Bleuler, 1911).

Because of the difficulties of classifying individual psychopathologies, according to DSM-IV, schizophrenia is classified as being present in subjects displaying at least two of the following symptoms for at least a week:

1. Disorders of cognition

Schizophrenics can suffer pervasive thought disturbance. They appear to have difficulty suppressing the irrelevant, both internal thoughts and external stimuli.

2. symptom 2

3. symptom 3

However, treating schizophrenia as a single phenomenon with multifarious symptoms results from the history of its discovery.

causes of schizophrenia

twins with schizophrenia

demonstrates that the cause cannot be solely genetic, though 50% of the variety is genetic.

treatments

There are five dopamine receptors, but it is the D2 variety which chlorpromazine blocked, first formulated in 1952.

conclusion