Veterinary Neuropharmacology

CHEMICAL MESSENGERS

• Neurotransmitters: substances stored in the presynaptic area in vesicles. On release lead to excitation or inhibition.
  • Many neurotransmitters have been discovered so far (almost 100).
  • Most important ones are:
    • Biogenic amines -- Histamine, 5-HT, Adrenaline, Noradrenaline, Dopamine, ACh
    • AminoAcids – GABA, Glycine, Glutamate, Aspartate
    • Peptides – Somatostatin, Substance P, enkephalin, Endorphin, Oxytocin, Vasopressin, Cholecystokinin, Thyrotrophic hormone, Angiotensin, Vasoactive intestinal peptide, Neuropeptide Y.
• Neurohormones: Hormone arising from a neuron. Eg: oxytocin, vasopressin.
• Neuromodulators: Originates from cellular and nonsynaptic sites, influence the general level of excitability without altering the membrane potential. Eg: ammonia, CO₂, Prostaglandins, steroid hormones.
• Neuromediators: Those that participate in the elicitation of response to a transmitter. Eg:Second messengers cAMP, cGMP, IP₃.