Behavioral Neuroscience Summers

text:The Basis of Neuropharmacology 8th Edition - Cooper, Bloom, Roth:read Chapter 105-127 Rhythmicity & Behavior Sensory input for Rhythmicity Afferent path to the SCN Circadian Rhythms Efferent SCN output Integration of Rhythms into Behavior end     Acronyms/Abbreviations     Syllabus

Glu VIP AVP GABA 5-HT Figures of Rhythmicity Retina-RGC-SCN Molecular SCN

BIOLOGICAL RHYTHMS
VIII. g-aminobutyric Acid (GABA) 			

	A. NH2-CH2-CH2-CH2-COOH 
 
		1. formed from Glu by L-glutamic acid decarboxylase (GAD) 
 
			a. GABA shunt: bypass from Kreb's to provide glutamate 
 
			b. GABA catabolized by GABA-T
			  (GABA transaminase = a-ketoglutarate aminotransferase) 
			  
				i. NH3 to glutamate synthesis 
 
		2. inhibitory amino acid transmitter = inhibits firing of neurons 
 
 
	B. Receptors - 2 major types   
 
		1. GABAA = ligand-gated Cl- channel 
 
			a. postsynaptic inhibition: hyperpolarizing
			   postsynaptic membrane
					
				i. influx of Cl- 
 
			b. GABAA on GABA neurons is functionally
			   presynaptic inhibition  
 
			c. 5 subunits - 2a + 2b + 1g  (usually) 
 
				i. a binds benzodiazepines (valium) 
 
				ii. b binds GABA
					
					
				iii. other sites near membrane bind barbiturates, anesthetics,
				     alcohols and H2O, neuroactive steroids; and
				     inside bind convulsants and picrotoxin 
 
				iv. extraordinary structural diversity: a1-6, b1-4, g1-3, d, e, q, r1-2 

					(1) yields functional diversity 
 
				v. superfamily of ligand gated channels including
				   nicotinic, 5-HT3, NMDA, AMPA, KA & glycine-R 
 
 
			b. GABAB 	(fewer) 
 
				i. often presynaptic
  
					(1)G K+ ® open K+ or close Ca++ channels

						(a) autoreceptors inhibit GABA neurons
						    by hyperpolarization
						
					(2) also Gi® X AC

				ii. sometimes postsynaptic 
				
					(1) ­ phospholipase A2 ® ­ cAMP 


			c. GABAC in retina
	
				i. more sensitive Cl- channel


			d. GABA transporter (GABAT)


	C. GABA GHT projections, IGL to SCN shell neurons colocalize NPY  
 
		1.  GABA interneurons in SCN core (with VIP/GRP)
		   and shell (with AVP/calretinin)
		   
			a. intrinsic neurons in cortex, hippocampus, cerebellum,
			   olfactory bulb and retina... 

		2. projections from hypothalamus to cerebral cortex

			a. direct pathway for limbic, emotional, and visceral 
			   information to reach the cortex 
 
		3. projections of striatum to substantia nigra