Summers

Neurobiology Spring 2000 click here for text only acronyms

text: Fundamental Neuroscience - Zigmond, et al.,: Read pages 1127-1176 for this lecture end

XXXIV. Integration of Neural control and Endocrine modulation:
 Reproductive Behaviors - Lordosis 			back to XXXIII. Neuroendocrine Regulation

	A. Reflex - stimulated by tactile sensory input of
	   male body against females rump (rats)
													   

		1. requires input from the brain


	B. afferent information in fibers of anterolateral spinal columns


		1. to 3 sites: 


			a. lateral vestibular nucleus (LVN): postural control


			b. medullary and midbrain reticular formations + midbrain central gray

		
				i. midbrain central gray: integrates autonomic, limbic,
				   sensory & motor information


				ii. midbrain reticular formation: brain arousal


				iii. medullary (+ pontine) reticular formations:
				     modulation of muscular reflexes


	C. E2  primes neurons of the ventromedial hypothalamus = VMN


		1. CeA, hippocampus and midbrain central gray
		   also concentrate E2


		2. raises the level of tonic activity


		3. ­ axon terminal levels of GnRH


		4. GnRH potentiates neurons of the midbrain central gray 


			a. threshold facilitation necessary


	D. E2 is followed by a short burst of P prior to lordosis


		1. P: fast response - intracellular and membranal receptors


		2. P inhibits 5-HT


			a. 5-HT tonically inhibits behavior


			b. P disinhibits system


	E. accessory olfactory (vomeronasal) information potentiates E2/P effects


		1. olfactory/accessory olfactory neurons secrete GnRH


			a. hypothalamic GnRH develops ontogenetically from olfactory tissue 


		2. visual input, e.g. presence of the male, also facilitates response 


	F. Sensory information is integrated by the limbic system


		1. modular sensory information from association cortices to amygdala

							                  stria
			a. olfactory « corticomedial  ®  bed n. of stria terminalis ® VMN
							                terminalis

				i. recognize male scent and respond


			b. CeA ® VMN


				i. mediates action of behavioral response


					(1) stress ® corticosterone (B) ® ­ 5-HT release


						(a) 5-HT inhibits behavior


					(2) P + B ® ­­ 5-HT


						(a) stronger inhibition timed for the short period when
						    P normally disinhibits behavior


		2. integrated sensory information from association corticies to hippocampus


			a. CA1-4 ® learning appropriate environmental
			   context for sexual behavior


				i. appropriate context stimulates behavior


				ii. inappropriate context should block behavior


	G. midbrain reticular formation (reflexive arousal) +
	   midbrain central gray (hormonal + neuromodulator potentiation)
	   neurons activate medullary reticular neurons


	H. Reflex can now be completed via medullary reticular formation 


		1. project through reticulospinal tract to ventral horn motor neurons


	I. Efferent spinal neurons stimulate contraction of back muscles


		1. behavior facilitated by postural adjustments
		    stimulated by LVN neurons

XXXV. Circadian Rhythms

Top