Behavioral Neuroscience, lecture on integrated circuitry/neurochemistry of Lordosis
USD Department of Biology
Behavioral Neuroscience
Summers
Sexual Behavior
Reflexes
Sensory Reception - Tactile Receptors
Spinal Synapses
Ruffini Endings 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
LORDOSIS
XV. Integrated View of Lordosis  	

	A. Stimulating the Behavior


		1. Full behavior (3 pt severe dorsiflexion, head up) requires
		   stimulation of Ruffini organs
		   
		   	a. pressure stimulation of rump and flank
	
			
			b. potentiated by E2 and coitus
		
			
			c. potentiated by pacing and proceptive behavior
			   (see D. 1. mPOA)
			   
			   	i. hopping and darting

		
		2. Partial behavior (1 or 2 pts) can be stimulated by
		   ancillary events
		   
		   	a. context is important (see D. Modifying the Response - Limbic Modulations)
			
			b. smelling or sighting male
		
		
	B. Basic Reflex
	
	
		1. Reflexes are Spinal Cord events
		
			a. afferent to interneurons to efferent motor neurons
			
				i. pudendal afferents: Glu, SP, VIP, Enk, somatostatin
			
			b. insufficient to produce Lordosis
			
				i. GABAA inhibition of motor output


		2. Synergistic input to motor neurons recruited
		
			a. ascending signals from spinal cord interneurons
			   kindle synergistic descending stimulation
			   
			   	i. insufficient

			
			b. hormonally driven gated response from VMN in the
			   hypothalamus permits descending stimulation of
			   motor neurons
			   
			   	i. via medullary reticular formation
				  (reticulospinal projections)
			
				ii. sufficient

			
	C. Gating - Priming and Disinhibition
	
	
		1. E2 makes descending pathway viable (priming)
		
			a. excitable GnRH, SP, PrL and HP70 neurons from VMN to MCG
			
			b. contextual stimuli can add to the excitability
			   (see D. Modifying the Response - 2. Limbic Modulations)

		
		2. P releases them
		
			a.  by inhibiting 5-HT (disinhibition)

		
		3. Necessary and Sufficient

		
	D. Modifying the Response - Limbic Modulations

		1. mPOA stimulates Pacing but inhibits Lordosis
		
			a. inhibition of lordosis during pacing
			   POAVTAMCG
			
			b. inhibiting pacing: locomotion, approach and courtship
			   permits lordosis
			   
			   	i. E2 and 5-HT2A/C
			
			c. pacing promotes lordosis
			
			
		2. input to VMN from Amygdala, Hippocampus and Olfactory Bulb
		   and locus ceruleus promotes (or inhibits) lordosis 

			a. NE, ACh, Oxy stimulate VMN neurons
			
				i. GABA and Enk stimulate by inhibiting 5-HT
			
			b. appropriate contextual input alone can stimulate
			   partial lordosis
			
			
	E. Motor Cascade
	
		1. Medullary Reticular formation provides descending stimulation
		   for lordosis reflex, and is stimulated 3 ways
		   
		   	a. ascending interneurons MRF
			
			b. gated VMN output MCG MRF
			
			c. midbrain reticular formation MRF
			
			d. MRF reticulospinal and LVN vestibulospinal efferents work togther
		
		2. Synergistic MRF  (+ LVN) output stimulates spinal cord motor neurons
		
			a. overrides GABAA inhibition

		
	F. Dorsal Root Afferents/Interneurons together with
	   Medullary Reticular Formation output complete the reflex

		1. Spinal motor neurons secrete ACh

		2. lateral longissimus and transversospinalis muscles contract and
		   dorsiflex spine 
		       
		3. Lordosis


	G. Copulation

		1. completion of the behavior

		2. promotes fuller expression of behavior

Syllabus