Nicotine

NICOTINE
  • Nicotine is an alkaloid obtained from the tobacco plant Nicotiana tobaccum it has no therapeutic effect ad is potent poison.
  • Nicotine first stimulates the nicotinic receptors in the autonomic ganglia and then causes their blockade (especially in high doses) by producing persistent depolarization.

Pharmacological Effects

  • Central nervous system
    • Nicotine transiently stimulates and then severely depresses the CNS. Death results from paralyzing diaphragm and chest muscle which in turn causes respiratory paralysis.
    • The respiratory muscles are paralysed due to depolarizing block of the neuromuscular junctions in skeletal muscles.

Cardiovascular systems

  • When nicotine is injected intravenously it produces an increase in blood pressure due to stimulation of predominant sympathetic ganglia and adrenal medulla.
  • However high doses results in fall of blood pressure, that results from ganglionic blockade loss of motor tone, unlike blood vessels, heart has predominant vagal tone.
  • Hence small doses of nicotine or high doses of nicotine initially produce decrease in pulse rate. When the autonomic ganglia are blocked by high doses of nicotine the heart rate returns normal ad a relative tachycardia may be observed.

Gastrointestinal Tract

  • Small dose of nicotine enhance the parasympathetic tone and increased gastric secretion , vomiting, increased peristalsis and defecation. Blockade of autonomic ganglia may produce decreased tone and motility of GI tract and constipation.

Exocrine glands

  • Nicotine causes initial stimulation of salivary and bronchial secretions that is followed by predominant inhibition

Skeletal muscle

  • Nicotine initially stimulates nicotinic receptors in motor end plate and in large dose produces a depolarizing muscle paralysis.
Last modified: Sunday, 16 October 2011, 11:14 AM