Evaluation of prenatal androgen and ovarian secretions on receptivity in female and male rats.

A total of 102 male and 146 female offspring of Sprague-Dawley rats injected daily from Day 16 through Day 20 of gestation with either 2 mg of testosterone propionate (TP) in .1 ml of sesame oil or oil alone were tested for sexual receptivity following injections of 3.3 μg of estradiol benzoate (EB) and .5 mg of progesterone (P) beginning at 40, 80, or 120 days of age. At each age, neonatally gonadectomized males and females from TP-injected litters exhibited less receptivity than corresponding oil-injected controls. Prenatally androgenized females were similar to neonatally castrated oil-injected males at all ages. Ovarian implants from birth to 35 days of age significantly increased receptivity in neonatally castrated males and androgenized females. Increasing the age at which testing was initiated systematically reduced receptivity in all groups. (21 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Endomorphin-2 is an endogenous opioid in primary sensory afferent fibers

Evidence is presented that the recently discovered endogenous mu-selective agonist, endomorphin-2, is localized in primary sensory afferents. Endomorphin-2-like immunoreactivity was found to be colocalized in a subset of substance P- and mu opiate receptor-containing fibers in the superficial laminae of the spinal cord and spinal trigeminal nucleus. Disruption of primary sensory afferents by mechanical (deafferentation by dorsal rhizotomy) or chemical (exposure to the primary afferent neurotoxin, capsaicin) methods virtually abolished endomorphin-2-like immunoreactivity in the dorsal horn. These results indicate that endomorphin-2 is present in primary afferent fibers where it can serve as the endogenous ligand for pre- and postsynaptic mu receptors and as a major modulator of pain perception.     

Effect of ovarian secretions on female behavioral potentiality in the rat.

Measured receptivity in female Sprague-Dawley rats ovariectomized at 5 ages, in neonatally gonadectomized females and males implanted with ovaries, and in neonatally castrated males injected with estradiol benzoate (EB) or oil. Mean receptivity, darting, and lordosis scores were higher during the 1st 4-5 mating tests in females and males having ovaries prepubertally. In amounts greater than .01 mg., EB inhibited female behavior. Even after ovariectomy, body weight was lightest in males and females having ovaries for 60 days. Progesterone and EB decreased weight gain faster in Ss gonadectomized prepubertally. Results indicated that physiological amounts of ovarian hormones, while not necessary for development of female potentiality, permanently influence it by modifying rate of utilization of estrogen circulating during adulthood. (24 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Facilitation of receptivity in estrogen-primed rats during successive mating tests with progestins and methysergide.

Evaluated the role of hormonal and experiential variables in mediating the gradual increase of receptivity occurring during weekly tests in 142 Sprague-Dawley adult ovariectomized females. Hormone treatment consisted of estradiol benzoate (EB) injection followed by progesterone, 20alpha-hydroxyprogesterone, methysergide maleate, or oil during weekly mating tests. The experiential conditions were vaginal stimulation, mounts only, or no interaction with males. There was a gradual increase in receptivity in all groups even in the one receiving oil. Progressive facilitation occurred even when no interaction with the male was permitted. Interchanging the synergists on the 6th and 7th tests was not detrimental to the display of receptivity attained with synergists given previously. Thus, it is concluded that successive injections of EB rather than synergists or experience mediate this increase in receptivity. (38 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of perinatal gonadal secretions on parameters of receptivity and weight gain in hamsters.

Examined the influence of ovarian and testicular secretions on lordosis in 64 female golden hamsters (Mesocricetus auratus) ovariectomized when 1 or 43 days old and in 80 males castrated when 1, 3, 5, or 43 days old. The 1st of 8 weekly 10-min mating tests was initiated at 57 or 113 days. Receptivity was not different among female groups except for higher initial scores for those with ovaries through puberty. Initial and maximum receptivity in males was inversely proportional to castration age. Rate of decrease from maximum appeared higher in males castrated at Days 3 and 5 than at Day 1. Age of initial test was significant for males; older Ss had lower initial and maximum receptivity scores. Gonadal secretions decreased weights in both sexes. (15 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Modifications induced by neonatal steroids in reproductive organs and behavior of male rats.

112 3-day-old male Sprague-Dawley rats were injected neonatally with .01, .1, 1, 10, 100, or 1,000 μg of estradiol benzoate (EB), 10,000 μg of testosterone propionate (TP), or sesame oil; they were subsequently examined for testicular, penile, and accessory organ development. Sexual behavior was evaluated during therapy with fluoxymesterone (FM) and then with TP. EB in dosages greater than 1.0 μg delayed testicular descent, reduced the size and hormone responsiveness of reproductive organs, and decreased sexual behavior in a dose-dependent manner. The 10,000 μg dosage of neonatal TP delayed testicular descent and reduced sexual behavior to levels near those of the 10–200 μg EB groups, but it produced no significant penile or accessory organ changes. Neither reduced peripheral organ development nor inhibited neonatal testicular secretions fully explain reductions in male behavior following large dosages of neonatal TP. Neonatal androgen may reduce the responsiveness of CNS neurons governing male sexual behavior after being converted to estrogen or by directly altering steroid receptor systems. (32 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)