This document discusses neurotransmission in the autonomic nervous system. It describes how neurotransmitters are released from nerve terminals and activate receptors on target cells. The two main types of neurotransmission are adrenergic (using norepinephrine) and cholinergic (using acetylcholine). Neurotransmission can be modulated through presynaptic, postsynaptic, and other mechanisms. Multiple neurotransmitters may also be released together to have synergistic or opposing effects.

1. INTRODUCTION TO AUTONOMIC PHARMACOLOGY: Part III Mechanism of neurotransmission at in the autonomic nervous system

2. General Features of Peripheral Autonomic Neurotransmission NT = Neurotransmitter

3. General Features of Peripheral Autonomic Neurotransmission Membrane Depolarization of Pre- or Postganglionic Fiber Calcium Entry into Varicosity Exocytosis of NT Diffusion of NT Across Neuroeffector Junction or Synapse Activation of NT Receptors Depolarization of Postganglionic Fiber or Response of Effector Cell Nerve Impulse

4. Sympathetic Postganglionic Fiber Effector Cell Neuroeffector Junction COMT (Liver) SUMMARY OF ADRENERGIC NEUROTRANSMISSSION

5. Summary of Catecholamine Biosynthesis Tyrosine DOPA Dopamine Norepinephrine Epinephrine ADRENAL GLAND SYMPATHETIC NERVE

6. Parasympathetic/Sympathetic Preganglionic Fiber or Parasympathetic Postganglionic Fiber Neuroeffector Junction Parasympathetic or Sympathetic Postganglionic Fiber or Effector Cell SUMMARY OF CHOLINERGIC NEUROTRANSMISSSION

7. COTRANSMISSION Release of More Than One Neurotransmitter from the Same Nerve Terminal Cotransmitter B Synergistic or Opposite Actions Cotransmitter A

8. Types of Postsynaptic Synergism Norepinephrine/NPY Norepinephrine/ATP

9. Example of Postsynaptic Synergism: (NPY enhances actions of NE) NPY 10 nM NE NE Perfusion Pressure (mmHg)

10. Example of Postsynaptic Synergism: ATP mediates fast response NE mediates slow response Control Prazosin Prazosin + Suramin Control Suramin Prazosin + Suramin

11. Many Examples of NANC Neurotransmitters

12. Many Examples of NANC Neurotransmitters

13. MODULATION OF NEUROTRANSMISSION Modulation of Neurotransmisson Presynaptic/ Prejunctional Modulation Postsynaptic/ Postjunctional Modulation Presynaptic/ Prejunctional Inhibition Presynaptic/ Prejunctional Facilitation Postsynaptic/ Postjunctional Inhibition Postsynaptic/ Postjunctional Facilitation

14. MODULATION OF NEUROTRANSMISSION From Nerve Terminal Being Modulated (e.g., Autoinhibitory Feedback) From Postsynaptic/ Postjunctional Site (e.g., Trans- synaptic/ Transjunctional Inhibitory Feedback) From Nearby Nerve Terminal (Cross- talk) From Remote Site via Circulation (e.g., Renin Release) Sources of Modulators of Neurotransmission

15. Mechanisms of Neuromodulation NE Ach NE Ang II +

16. Mechanisms of Neuromodulation Epi