Biology of Reproduction

XXIV. Pheromones                          back to XXIII. Sexual Response and Behavior

	A. exocrines which change physiology or behavior
	    of another individual

		1. regulated by hormones

	B. sexual attractants are pheromones

		1. releasing pheromones trigger a rigid stereotyped response

			a. typical of insects

		2. signaling pheromones elicit complex modifiable responses
		    to chemical cues

			a. sensed primarily by accessory olfactory (vomeronasal)
			    organs in vertebrates

				i. linked neurally with limbic and hypothalamic
				    nuclei controlling reprodcution and  sexual behavior

					(1) GnRH cells in adult hypothalamus originate
					    as accessory olfactory neurons and migrate
						to the POA and ARC

				ii. human VNO is electrophysiologically stimulated
				     by skin or axillary extracts

					(1) androstenes activate female VNO more

						(a) women are attracted to scents of men
						    that are most unlike themselves in
							MHC genes major histocompatibility complex

					(2) estrenes activate male VNO more

			b. vaginal secretions of female hamsters
			    contain aphrodisin

				i. attract males

				ii. stimulate sexual behavior

					(1) olfactory lesions completely block
					    courtship and sexual behavior

					(2) vaginal secretions applied to the
					    hindquarters of males makes that
						male sexually attractive to other males

				iii. learned

					(1) can be conditioned

						(a) androgens ­ attractiveness of vaginal
						     secretions in both males and females

			b. androgens can be pheromones

				i. androgens secreted into salivary glands
				    of male pigs

					(1) androgen becomes airborne by exhalation

						(a) induces lordosis in receptive females

				ii. T in male mouse urine elicits ­ aggression
				     from other males

			c. estrogens can be pheromones

				i. E2 secreted onto the skin of female
				    garter snakes attract many males and stimulate
					formation of mating ball

			d. prostaglandins can be pheromones

				i. the same PGF2a released during
				    ovulation are released into the water and
					trigger sexual behavior in male goldfish

			d. pheromones in urine of estrus female rat:

				i. signals estrus to male

			e. copulins from female Rhesus monkeys

				i. ­ male sex drive

			f. humans

				i. copulins are in vaginal secretion
				    near ovulation

					(1) vaginal secretions near ovulation
					     are most attractive to men

					(2) vaginal secretions applied to women
					     ­ their sexual attractiveness

				ii. axillary secretions ­ attractiveness

	C. priming pheromones induce physiologcial changes in the
	   recipient (usually takes 48h)

		1. D male reproductive physiology

			a. hamster vaginal secretions ® quick elevation of male T

				i. reduce aggression

			b. progestins can be pheromones

				i. goldfish female preovulatory follicles
				    secrete progestins into the water

					(1) ­ gonadotropins ® ­
						 sperm production in males

		2. D female reproductive physiology

			a. pheromones in urine of mature male mice:

				i. synchronize estrous cycles

			b. pheromones from female mice suppress ovarian function

				i. probably by ¯ LH and  FSH

			c. pheromones from male prairie voles
			    activate ovarian estrogen secretion

				i. estrus and ovulation do not occur
				    in the absence of males

		3. humans

			a. musk-like oders can be smelled by adult women;
			    not by children or males

				i. only near ovulation 

			b. axillary secretions synchronize menstrual cycles
			    for cohabiting women

			c. frequency of exposure to men (axilla)
			    can influence menstrual regularity

	D. gamones induce sexual development (also priming)

		1. mature male mice urine also

			a. speeds puberty in females

			b. female urine delays puberty

		2. nipple pheromone in rabbits

			a. enables young to locate and grasp nipple

	E. allomones and kairomones are interspecies attractants

XXV. Sexually Transmitted Diseases