CNS PHARMACOLOGY 2 - PowerPoint PPT Presentation

1 / 12
About This Presentation
Title:

CNS PHARMACOLOGY 2

Description:

GABA is an inhibitory neurotransmitter (receptor on Cl- channel) ... also emetic effects (CTZ in medulla) DOPAMINE. Treatment of Parkinson's Disease ... – PowerPoint PPT presentation

Number of Views:3450
Avg rating:3.0/5.0
Slides: 13
Provided by: elaine92
Category:

less

Transcript and Presenter's Notes

Title: CNS PHARMACOLOGY 2


1
CNS PHARMACOLOGY 2
  • CNS drugs which influence
  • GABA
  • Dopamine

2
GABA
  • GABA is an inhibitory neurotransmitter (receptor
    on Cl- channel)
  • Drugs which enhance GABA are CNS depressants (and
    muscle relaxants, anti-epileptics) - mostly bind
    to receptor and open the Cl- channel
    (hyperpolarise)
  • - benzodiazepines (eg valium)
  • - barbiturates (eg thiopentone)
  • - alcohol

3
GABA
  • a) Drugs for anxiety and insomnia
  • BZDs - short and longer acting
  • ? sleep (selective for ? anxiety
  • RAS which regulates (limbic system)
  • sleep/wake cycle)
  • other CNS depressants ? respiration

4
GABA
  • BZDs - adverse effects
  • - anterograde amnesia
  • - tolerance (to anxiolytic effects)
  • Barbiturates
  • - similar action,but ? respiratory centres
  • - ? enzymes in liver (? drug metabolism)
  • - less safe, little used except for seizure
    control and anesthesia

5
GABA
  • b) Drugs for epilepsy
  • when neurons easily depolarised ? seizure
  • drugs used inhibit neuron discharges by
  • - potentiating action of GABA
  • eg barbiturates (phenobarbitone), valproic
  • acid, diazepam for status epilepticus
  • - reducing spread of seizure by closing Na
  • channels eg phenytoin

6
GABA
  • Tolerance to CNS depressants can lead to physical
    dependence
  • Anti-epileptic drugs should not be withdrawn
    suddenly
  • Cross-tolerance occurs between BZDs,
    baarbiturates and alcohol (all affect GABA)

7
DOPAMINE
  • 3 major pathways in brain associated with
  • - thought (cortex)
  • - movement, affected in PD and side-effects
  • to antipsychotic drugs (nigrostriatal path
  • to basal ganglia of forebrain)
  • - endocrine control (prolactin - pituitary)
  • also emetic effects (CTZ in medulla)

8
DOPAMINE
  • Treatment of Parkinsons Disease
  • - due to DA ? in nigrostriatal pathway
  • - treat by
  • (i) ? DA by ? L-dopa (DA precursor)
  • and carbidopa (to ? peripheral metabolism)
  • (ii) DA receptor agonist (apomorphine)
  • (iii) anticholinergic drugs to ? ACh, restore
  • DA/ACh balance on movement control

9
DOPAMINE
  • Side-effects in PD treatment
  • Acute (some tolerance)
  • - nausea
  • - hypotension
  • - psychological (schizophrenia-like)
  • Chronic
  • - after 2 years of L-dopa involuntary
    movements

10
DOPAMINE
  • Treatment of schizophrenia (psychosis)
  • - symptoms
  • positive delusions, hallucinations
  • negative social withdrawal
  • - antipsychotic (neuroleptic) drugs can reduce
    positive symptoms
  • - effective drugs are antagonists at DA
    receptors (eg haloperidol, chlorpromazine)

11
DOPAMINE
  • Etiology of schizophrenia - possible primary
    defect is ? activation of CNS receptors for DA in
    cortex
  • Side-effects of drugs are extrapyramidal motor
    effects due to action in basal ganglia
  • Acute manageable with anti-ACh drugs
  • Chronic irreversible (tardive dyskinesia)
  • Low-potency drugs also block ACh receptors ?
    better DA/ACh balance

12
DRUG DEPENDENCE
  • Drugs which cause dependence have reinforcing
    (rewarding) properties often due to ? DA release
  • ? ? euphoria
  • ? ? anxiety and stress
  • May ? physical dependence, due to adaptive
    changes in neurons (an abstinence syndrome
    occurs)
  • Psychologic dependence (craving)
Write a Comment
User Comments (0)
About PowerShow.com