AUTONOMIC NEUROTRANSMITTERS

1/31/89, rvsd 1/28/94, 1/31/95, 1/30/97, 2 February 04, 4 Feb 08

Solomon & Davis, p 342, Thibodeau & Patton, p 364-365, Tortora & Anagnostakos, 363-364), DeGraaf & Fox, 426-427 & 510-512, Tortora and Evans, 2nd, 341-347, Martini 6^th: 543-545, 7^th: 529-533

AUTONOMIC TRANSMITTERS

Adrenal medulla served by splanchnic nerve, activating chromaffin cells (modified post-ganglionic cells), release 20% norepinephrine and 80% epinephrine

SYMPATHETIC RECEPTORS:

ADRENERGIC TRANSMISSION:

Most sympathetic post-ganglionic fibers release norepinephrine

                                       Exceptions:     sweat glands, uterus, and pilomotor which release acetylcholine

Catacholamines generally inactivated by reuptake, but also by

Monoamine oxidase (MAO) (found on mitochrondria membranes) (slow)

Adrenergic Receptors determine the effect of the neurotransmitter:

alpha receptors:           alpha₁: inhibits adenylate cyclase (causes vascular sm musc to constrict)

(stim apocrine sweat)     alpha₂: mobilization of Ca⁺

beta receptors:             beta₁ or beta ₂: both activate adenylate cyclase in membrane (dilate)

                                       stimulates heart rate and force

ADRENERGIC DRUGS:

Epinephrine:                  acts on alpha and beta receptors, used to treat asthma, relaxes respiratory passages, reduce swelling

Isoproterenol:                acts on beta receptors, cardiac resuscitation

Phenylephrine:               acts on alpha receptors, decongestant, constricts nasal vessels.

Ephedrine:                     stim release of norepi, original adrenergic drug, asthma, allergic disorders, stim heart.

Amphetamine:               causes accumulation of norepi in synapses, used to be used to treat narcolepsy, hyperkinetic children.

ADRENERGIC BLOCKING DRUGS:

Reserpine:                      blocks synth and storage of norepinephrine, treats hypertension, some psychotics intolerant of phenothiazines

Propranolol (Inderal):    beta blocker, relieve pain in angina, reduces heart rate and force, control migraines. treats hypertension

PARASYMPATHETIC RECEPTORS:

Nicotinic:                       found on both para and symp post gang receptors, ACh and nicotine (nausea, convulsions, twitching,) have same action on these.

Muscarinic:                    on all effectors enervated by postganglionic parasympathetic axons,

CHOLINERGIC DRUGS:

Pilocarpine:                    stimulates muscarinic receptors, constricts iris

CHOLINERGIC BLOCKERS:

Atropine:                        blocks muscarinic receptors, surgery prep, inhibits salivation, secretions, dilate pupils

Scopolamine:                 blocks muscarinic receptors, motion sickness, in labor to promote drowsiness with amnesia (twilight sleep)