Behavioral Neuroscience Summers

Sexual Behavior Reflexes Sensory Reception - Tactile Receptors Spinal Synapses Afferent Spinal Pathways

Hypothalamic Gating Efferent Motor Cascade Neuromuscular Production of Lordosis Integrated Story of Lordosis VIP Substance P Estrogens

5-HT GnRH ACh Lordosis figures   Sensory Receptors Spinal Cord   Lordosis Circuitry end     Acronyms/Abbreviations

LORDOSIS
XII.  Acetylcholine (ACh)
                                        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)

			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. transmitter for: motor neurons of the spinal cord
	    \ all skeletal neuromuscular junctions

		1. all autonomic preganglionic neurons

			a. parasympathetic postganglionic neurons

		2. cells in the caudate-putamen nucleus involved in motor coordination 

		3. 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

		4. 2 specific populations in the limbic system

			a. septum to hippocampus  & habenulo-endopeduncular projections

			b. short axon striatal cells

	C. Muscarinic and Nicotinic Receptors 	(membrane proteins)

		1. M1 - M5

			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++

					(1) M3 stimulates VMN neurons 
					    projecting to MCG to stimulate lordosis
				
				ii. M2,4 cAMP

		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
					    curving the spine during lordosis