Behavioral Neuroscience, lecture on Acetylcholine
USD Department of Biology
Behavioral Neuroscience
Summers
Rusty Crayfish Crayfish Escape Behavior
Crayfish Neuroanatomy
Fundamentals of Neurocircuitry
Sensory Afferent input for Tail Flip
Gating the Full Flip
Gating the Tail Flip for Upward Thrust
Parallel Gating of Crayfish Escape
Motor Neuron output for Crayfish Escape
Integration: Crayfish Escape
Acetylcholine ACh
GABA
5-HT
Crayfish figures
Crayfish Escape Neurocircuitry
end     Acronyms/Abbreviations
Escape - Crayfish
VI. Acetylcholine (ACh) 
         	Acetylcholine
	A. substrates: choline and acetyl CoA
	                       (diet)       (Glycolysis and Kreb's)
		        
		1. synthetic enzyme: choline acetyltransferase (CAT)

			a. cytosolic   (most is synaptic)
			
				i. vesicular transporter = vAChT necessary
				
					(1) package ACh for synaptic release

			b. CoA left over

			
		2. degradative enzyme: acetylcholine esterase (AChE)

			a. membrane protein

			b. catabolites = choline and acetate

			c. turnover = 150ms	or	5,000 ACh molecules/s

			
	B. Muscarinic and Nicotinic Receptors 	(membrane proteins)

		1. muscarinic M1 - M5    7tm

			a. slow response time (100 - 250 ms)

			
			b. act directly on ion channels 	

				i. open or close K+, Ca++, or Cl- channels

					(1) may lead to depolarization 
					   or hyperpolarization

					   
			c. and activate 2nd messenger system (via G proteins)
			
				i. M1,3,5 Gp(q)PLCIP3 & Ca++

				ii. M2,4 GiACcAMP  PKA  CREB  CRE


		2. Nicotinic

			a. four glycosylated peptide chains a, b, g, d in muscle
	
				i.  arranged with 2 a and 1 each b, g, d = 5 total
                			
			b. neuronal only a & b

				i.  arranged with 8 types of a + 3 types of b
                			
			c. ACh binds to the a subunit

				i. binding causes conformational change

					1) allows cations, not anions, to pass

						a) Na+ pases first, 
							depolarizing muscle cell membrane

					2) deporlarization  Ca++ release
						from ER stimulates muscular contraction
						 
	C. Central ACh Distribution in vertebrates: Involved in Learning
	
		1. ACh is produced in the nucleus basalis 

			a. projections to the cerebral cortex and many parts of the brain

			b. these cells degenerate during Alzheimer's disease

			
		2. ACh is in 2 specific populations in the limbic system

			a. septum to hippocampus  & habenulo-endopeduncular projections

			b. short axon striatal cells
	
	D. Autonomic NS
	
		1. all sympathetic and parasympathetic preganglionic neurons

		2. parasympathetic postganglionic neurons
	
	
	E. ACh in Crayfish: transmitter for mechanosensory neurons

		1. sensory neurons in vertebrates use Glu

		2. sensory neurons in some other invertebrates (leeches) are glutamatergic

	F. ACh as a transmitter for motor actions and coordination
	
		1. motor neurons 
	\ all skeletal neuromuscular junctions
		
			a. Invertebrates
		
				i. crayfish: motor neurons to abdominal muscles
                
				ii. Leech L, VE, DE, AE, HE
			
				iii. Aplysia gill and siphon  retraction
			
			b. Vertebrates motoneurons of the spinal cord
			
		2. Cells in the caudate-putamen nucleus involved in motor coordination 
		
		3. PPT and LPT innervation of substantia nigra	

VII. Gating the Full Flip