Behavioral Neuroscience, lecture on Efferent SCN ouput
USD Department of Biology
Behavioral Neuroscience
Rhythmicity & Behavior
Sensory input for Rhythmicity
Afferent path to the SCN
Circadian Rhythms
SCN outputs Efferent SCN output
Integration of Rhythms into Behavior
Figures of Rhythmicity
Molecular SCN
end  Acronyms/Abbreviations   Syllabus
XI. Efferent Circadian Output 			

	A. 3 Major paths for SCN efferents 
		1. Within SCN: between core and shell
			a. VIPcore® AVPshell; AVPshell ® VIPcore
		2. To and Through the SPVZ
			a. Anterior Hypothalamic Subparaventritcular Zone
			b. SPVZ is dorsal & caudal to SCN
				i. SCN shell projects to medial SPVZ
				ii. SCN core projects to lateral SPVZ
		3. To and Through the RCA
			a. Anterior Hypothalamic Retrochiasmatic Area
			b. RCA is dorsal & rostral to SCN
				i. reciprocal innervation
	B. Reciprocal innervation of SCN core and shell establishes the biological clock

C. SPVZ 1. Shell Fibers a. extend caudally to DMH i.part of sleep/wake regulatory centers ii. secrete clock gene controlled neuropeptides (their receptors also clock gene controlled) 1)VIP, cardiotrophin-like cytokine and prokineticin 2 b. AVP projections to the PVN i. confer circadian electrical activity in PVN 1) Glu & GABA connections also important ii. PVN regulates Neuroendocrine and Autonomic Functions 1) also Tob, behavioral state, and Pineal Melatonin c. two paths to the Habenula and Pineal Gland i. via Hypothalamus/Habenula & Pineal ii. via median forebrain bundle ® NST ® Spinal Cord Lateral Horn (sympathetic) NST ® SCLH ® superior cervical ganglion; SCG ® Pineal 1) LH ® ACh Nicotinic-R on SCG 2) SCG ® NE b2-R on Pineal iii. mammalian pineal has intrinsic rhythms, also clearly driven by SCN iv. pineal produces melatonin from 5-HT during darkness to regulate organismal rhythms and facilitate sleep 1) melatonin phase-shifts SCN = feedback 2) may coordinate rhythms longer than 1 day a) e.g. estrous/menstrual and circannual reproductive cycles iii. parietal eye (sharks, frogs, lizards) connects to pineal, and photoreceptive pineal (birds): Link pineal to environment 1) Pineal is the primary clock in some animals d. to BNST (bed nucleus of the stria terminalis) - anxiety and reproduction e. to Paraventricular Thalamus i. PVT projects rostrally to septum, amygdala, hippocampus, and cingulate cortex 1) circadian influence on memory, autonomic function, and affective tone ii. PVT also projects to the Nucleus Accumbens 1) applies circadian influence on motor integration and reinforcement/reward mechanisms 2. Core projections a. to ventral tuberal area (between VMN & ARC), b. PH c. lateral septum d. Periacqueductal Gray (PAG; MCG)
D. RCA 1. Shell projections a. small group of fibers anterior to AH and mPOA i. POA also part of sleep/wake regulatory centers ii. clock controlled VIP, cardiotrophin-like cytokine and prokineticin 2 2. Core projections a. to Basal Forebrain i. integrates circadian information with Behavioral State & Neocortical function b. to hypothalamus c. IGL i. indirectly (via RCA) innervates IGL d. brainstem, spinal cord ii. SCN/RCA/brainstem - circadian autonomic regulation iii. SCN/RCA/spinal cord - circadian sensorimotor integration e. projections overlap with those through SPVZ E. Projects both Stimulatory and Inhibitory output 1. Excitatory signals produced by Glu binding AMPA and NMDA receptors a. Also AVP (V1A) and VIP (VPAC2) outputs 2. Inhibition via GABA through GABAA receptors F. IGL 1. Optic nerve projections to the Lateral Geniculate Nucleus a. SCN ® RCA ® IGL 2. IGL has projections to midline thalamus, zona incerta, pretectal area / superior colliculus or optic tetum and back to SCN a. SCN/IGL/midline thalamic nuclei - influence circadian regulation of behavioral state b. SCN/IGL/subthalamic zona incerta - regulates circadian motor integration c. SCN/IGL/tectal zones - circadian visual functioning 3. IGL also innevates the median/dorsal raphé (d. raphé innervates LGN) a. mRaphé innervates SCN - 5-HT phase shifts rhythm
G. Redundancy 1. Multiple and Feedback inputs to control circadian rhythmicity in various functions 2. Rhythms of Autonomic Output through SCN/hypothalamus, SCN/PVT/limbic and SCN/RCA/brainstem projections 3. Motor rhythyms integrated via SCN/PVT/NAcc, SCN/RCA/spinal cord and SCN/RCA/IGL/zona incerta projections 4. Wake/Sleep/Activity Rhythms synergistically influenced by at least 3 systems: a. SCN through SPVZ to Hypothalamus b. SCN to RCA to Basal Forebrain c. SCN to IGL to midline thalamus

XII. Rhythm Integration