DRUGS ACTING ON THE CENTRAL NERVOUS SYSTEM

Learning Objectives

At the end this section the student will be able to:

1. Describe the major adverse effects of sedative hypnotic drugs.
2. Describe the drugs used in epilepsy.
3. Illustrate the approaches in the management of parkinsonism.
4. Explain the site of action, uses and adverse effects of antipsychotic drugs.
5. Describe the major adverse effects opioid analgesics.

INTRODUCTION

To facilitate the understanding of the pharmacological and unwanted effects of CNS drugs, the physiological functions of the main CNS neurotransmitters are discussed briefly.

Noradrenaline. Noradrenergic transmission is important in control of mood (functional deficiency resulting depression) controlling wakefulness, and alertness.

Dopamine. Dopamine is important in motor control (Parkinsonism is due to dopamine deficiency), has behavioural effects (excessive dopamine activity is implicated in schizophrenia), important in hormone release (prolactin, GH) and dopamine in chemoreceptor trigor zone causes nausea and vomiting.

5-HT. Physiological functions associated with 5-HT pathways include; feeding behaviour, behavioural response (hallucinatory behaviour), control of mood and emotion, control of body temperature and vomiting.

Acetylcholine(Ach). Ach has effects on arousal, on learning, and on short-term memory. Dementia and parkinsonism are associated with abnormalities in cholinergic pathways.

GABA. GABA is an inhibitory neurotransmitter in CNS.

Glycine is an inhibitory neurotransmitter, acts on GABA like receptor in the spinal cord.