Behavioral Neuroscience Summers

Fear Afferent Path for Fear Amygdala Fear Conditioning

Afferent Shock (US) Pathway Efferent Output Neuromuscular Production of Fear Potentiated Startle Integration of Fear Conditioning

ACh BDNF Gephyrin Enkephalin

Substance P Fear figures Fear Conditioning Circuitry end     Acronyms/Abbreviations

Fear Conditioning
IX. ACh = Acetylcholine 			
                                       O
		        I I
(CH3)3N+-CH2-CH2-O-C-CH3
	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)асPLCасIP3 & Ca++

				ii. M2,4 GsасACасcAMP ас PKA ас CREB ас CRE


		2. Nicotinic

			a. four glycosylated peptide chains a, b, g, d in muscle
	
			
			b. neuronal only a & b

			
			c. ACh binds to the a subunit

				i. binding causes conformational change

					(1) allows cations, not anions, to pass

					(2) Ca++ passing stimulates muscular contraction
					     of longitudinal, oblique, circumferential, and dorsoventral 
					     musculature
	
						 
	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 as a transmitter for motor actions and coordination
	
		1. motor neurons 
	\ all skeletal neuromuscular junctions
		
			a. Invertebrates
		
				i. Leech L, VE, DE, AE, HE
			
				ii. 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