Regional difference in the distribution of vasoactive intestinal polypeptide-immunoreactive nerve fibres along the uterus and between myometrial muscle layers in the rat

To investigate a possible regional variation of the vasoactive intestinal polypeptide innervation in the uterus of the cyclic rat, the distribution of vasoactive intestinal polypeptide-containing nerve fibres from the cervix to the oviduct end of the uterine horns was studied using immunohistochemistry. Immunoreactive nerve fibres were most concentrated in the cervix, where they formed a dense plexus in association with the musculature and surrounding blood vessels. In the uterus, a clear regional distribution of the vasoactive intestinal polypeptide innervation was observed. Numerous vascular and non-vascular immunoreactive nerve fibres were present in the lower part of the uterine horns, whereas they were sparse in the median region and absent at the oviduct end. Moreover, non-vascular peptide innervation was mostly concentrated in the circular layer of the myometrium and also occurred in the endometrium. Only a very few immunoreactive nerve fibres were presen t in the longitudinal muscle layer. No change in the peptide innervation pattern was observed during the different stages of the sexual cycle. The marked regional distribution of the peptide innervation in the rat uterus suggests that the regulatory effects of the peptide occur mainly in the lower part of the organ and principally affect the circular muscle layer in the myometrium.     

Differential effects of oestrogen on developing and mature uterine sympathetic nerves

Oestrogen is a key factor in the remodelling of uterine sympathetic nerves during puberty and the oestrous cycle; these nerves are influenced by changes in their target uterine tissue. The magnitude of oestrogen-induced responses might however be influenced by the maturation stage of sympathetic nerve fibres, the age of the neurons and/or the developmental state of the uterus. We have therefore compared the sympathetic innervation of the uterus following chronic oestrogen treatment of infantile/prepubertal and young adult intact and ovariectomised rats. Treatment of infantile/prepubertal rats resulted in the complete loss of intrauterine noradrenaline (NA)-labelled sympathetic nerves and a marked reduction in the total NA content in the uterine horn. Chronic treatment of young adult rats had little effect. To examine whether the age of the neurons or the degree of development of the uterus determined responsiveness of nerves to oestrogen, we assessed the effects of oestrogen on the sympathetic reinnervation of intraocular transplants of young adult uterine myometrium into ovariectomised adult host rats. Early treatment (10 days post-transplantation) resulted in less sympathetic innervation than late treatment (30 days post-transplantation). Measurements of nerve growth factor (NGF) levels in the uterine horn of control rats before and after puberty and following infantile/prepubertal chronic oestrogen treatment and acute oestrogen treatment of young adult rats revealed a coordinated increase between the growth of the uterus and NGF protein levels. Thus, developing and recently regrown sympathetic nerves are more susceptible to oestrogen-induced changes in the uterus than mature nerves, differential susceptibility is not related to the age of the neurons or the developmental state of the uterus and changes in NGF protein do not account for the differential susceptibility of developing and mature uterine sympathetic nerve fibres to oestrogen. Growing sympathetic fibres are more vulnerable to oestrogen than mature fibres and nerve fibres that have been in contact for longer periods with their target become less susceptible to oestrogen.     

Comparative histochemical distribution of nerve fibres storing noradrenaline and neuropeptide Y (NPY) in human ovary, fallopian tube, and uterus

Nerves containing noradrenaline were studied by formaldehyde-induced fluorescence and neuropeptide Y (NPY) was visualised by immunohistochemistry in the human ovary, Fallopian tube and uterus. All structures were richly supplied with noradrenergic fibres closely associated with the vascular and non-vascular smooth musculature. NPY-containing nerve terminals were consistently fewer, particularly in the ovary. The best developed nerve supply was found in the tubal isthmus and uterine cervix. Vessels were usually innervated by plexuses of nerves, containing NPY as well as noradrenaline. The discrepancy between the number of the two types of histochemically distinguishable nerves suggests that, if noradrenaline and NPY are co-localised in one and the same nerve, this is not a constant phenomenon in the human female reproductive tract.     

The bovine tubouterine junction: general innervation pattern and distribution of adrenergic,cholinergic, and peptidergic nerve fibers

The innervation of the bovine tubouterine junction was studied in sexually mature heifers using antisera against various neuronal markers and a modified acetylcholinesterase method. The vast majority of the nerve fibres in the bovine tubouterine junction belongs to the sympathetic nervous system; peptidergic and cholinergic fibers are restricted to characteristic locations. The endosalpinx in the adovarian portion of the terminal tubal segment is poorly innervated. The mucosa of the aduterine portion and of the tubouterine transitinal region proper receives a strikingly dense innervation, which is observed mainly in combination with a strong vascularisation of specialised mucosal structures. In the endometrium, perivascular nerves accompany the ascending spiral arteries but sporadic contacts between nerve fibres and uterine glands are also observed. From the muscular coat the inner longitudinal layer of the terminal tubal segment is more richly supplied by nerve fibres than the intermediate circular and outer longitudinal layers of the tubouterine junction. No changes in the innervation pattern were seen during the different stages of the sexual cycle.     

Noradrenergic and cholinergic nerves in the uterus of the Japanese long-fingered bat,Miniopterus schreibersii fuliginosus,change with reproductive cycle

The pattern of uterine innervation by noradrenergic (NA) and acetylcholinesterase-positive (AChE) nerves in different reproductive stages of the adult Japanese long-fingered bats were investigated histochemically and immunohistochemically. In the non-pregnant bat, the uterine horn was supplied with abundant NA and AChE nerves. These two types of nerves were closely associated with the uterine arteries and myometrial smooth muscles. In the pregnant bat, NA and AChE nerves supplying the uterus did not degenerate much during hibernating period, but reduced markedly after arousal. In the postpartum bat, the density of nerves recovered progressively. The significant change in the innervation pattern of uterine NA and AChE nerves in the pregnant bats under and after hibernation, and in the postpartum bat must be considered in relation to the adrenergic and cholinergic controlling mechanisms on the uterine function that is matched for the unique reproductive cycle of this bat.     

Involvement of perivascular neuropeptide Y nerve fibres in uterine arterial vasoconstriction in conjunction with pregnancy

The perivascular neuropeptide Y (NPY) innervation and its relation to adrenergic nerves of uterine arteries from non-pregnant and pregnant guinea pigs was analyzed immunocytochemically. The NPY content of the uterine artery was, in addition, measured radioimmunologically (RIA). Vasomotor effects of NPY per se and in combination with other vasoconstrictors were examined using a sensitive in vitro method. Pregnancy did not visibly affect density and distribution of NPY-immunoreactive fibres. The NPY fibres contained in addition immunoreactivity to dopamine-beta-hydroxylase (marker for noradrenergic neurons). RIA revealed a slight decrease of NPY content during pregnancy, probably due to the increased smooth muscle volume of uterine arteries. The contractile effect of NPY on uterine arteries was weak, while vasoconstriction induced by various agonists was potentiated by NPY, particularly during pregnancy. It is concluded that perivascular NPY-containing nerve fibres may be involved in the dramatic blood flow alterations that occur in the uterine circulation in connection with pregnancy and partus.     

Sympathetic and sensory innervation of the urinary tract in young adult and aged rats: a semi-quantitative histochemical and immunohistochemical study

Summary The sympathetic innervation of the urinary tract of young adult (4 months) and aged (24+ months) rats has been examined by glyoxylic acid-induced fluorescence for the detection of noradrenaline and by immunofluorescence using antisera against tyrosine hydroxylase (TH) and neuropeptide Y (NPY). Immunostaining for calcitonin gene-related peptide (CGRP), known to be present in pelvic sensory nerves, was also performed. Semi-quantitative estimations of nerve densities were made of noradrenergic and peptidergic fibres innervating the smooth musculature of the ureter, bladder and urethra, and of the urinary tract vasculature. In the aged rats the overall patterns of innervation remained unchanged. However, with the exception of the vesical vasculature, the density of noradrenergic innervation decreased as did the intensity of histofluorescence. A similar pattern of results was observed by TH and NPY immunofluorescence. The results present evidence for a diminution in the sympathetic control of the urinary tract in aged rats. The pattern and density of CGRP-immunoreactive nerves was unchanged in the aged animals suggesting that pelvic visceral sensory innervation is more resistant to the effects of advancing age.     

Mechanical responses of the rat uterus, cervix, and bladder to stimulation of hypogastric and pelvic nerves in vivo

Mechanical activities of the uterus, cervix, and bladder were recorded in vivo in anesthetized rats during electrical stimulation of either the hypogastric or pelvic nerve. Ovariectomized controls and hormone-treated groups were used as well as pregnant and postpartum rats. Stimulation of either hypogastric or pelvic nerve produced voltage- and frequency-dependent contractions of the three organs with no evidence of apparent inhibition. All evoked responses were completely abolished by tetrodotoxin, suggesting that these nerves are common pathways of innervation to the three organs. Atropine abolished uterine and cervical responses to both hypogastric and pelvic nerve stimulation, whereas bladder responses were only partly reduced. Hexamethonium almost totally blocked the evoked responses of the uterus and cervix. Phentolamine partly blocked uterine and cervical responses, and propranolol or physostigmine enhanced uterine and cervical responses to both hypogastric and pelvic nerve stimulation. These results suggest that motor innervation to the rat uterus and cervix is predominantly postganglionic cholinergic, with some alpha- and beta-adrenergic components, and that the bladder is innervated by mainly cholinergic and also noncholinergic nerves. Estrogen and estrogen-plus-progesterone pretreatment significantly increased the responses of uterus and cervix but not bladder. Uterine and cervical responses to either hypogastric or pelvic nerve stimulation were markedly reduced late in pregnancy and reappeared within 7 days after delivery.     

Changes of progesterone content of rat uterine flushings in relation to serum concentrations of progesterone during the oestrous cycle.

Uterine fluid was collected from four-day cyclic rats at each stage of the oestrous cycle and assayed for progesterone and protein content. Progesterone was determined by radioimmunoassay either after ethanol (or 2.5% NaOH) denaturation of proteins from uterine flushings ('total' progesterone) or without protein denaturation ('ether-extractable' progesterone). The amount of 'ether-extractable' progesterone in the lumen was constant from metoestrus to pro-oestrus (340 pg per uterus) but lower in oestrus (200 pg per uterus). However, 'total' progesterone content of uterine fluid was subject to cyclic variations and was highest in dioestrus (890 pg per uterus) and lowest in oestrus (350 pg per uterus), in contrast to serum progesterone which is lowest in dioestrus and highest in oestrus. Protein content of uterine flushings peaked to 780 micrograms per uterus in pro-oestrus then fell to about 140 micrograms per uterus until the end of the oestrous cycle. Changes in protein content of the lumen were followed by qualitative variations since the mean amount of 'bound' progesterone ('total' progesterone minus 'ether-extractable' progesterone) released per milligram of denatured lumen protein rose from 1.8 pmol in pro-oestrus to 18.2 pmol in dioestrus. The changes of luminal 'bound' progesterone during the oestrous cycle suggest that progesterone binding to luminal proteins could be an important modulator of progesterone action in rat uterus. Moreover, the variations in progesterone content of the lumen, irrespective of serum progesterone concentrations, are consistent with the hypothesis that progesterone synthesis occurs in the uterus.     

Effects of dexamethasone on estrogen- and pregnancy-induced plasticity in rat uterine sympathetic nerves

Estrogen and glucocorticoids are known to evoke opposing effects on the uterus. We analyzed the effects of dexamethasone (DEX) on uterine sympathetic denervation elicited by short- and long-term exposure to estrogen of intact prepubertal rats. We also studied the effects of DEX on the physiological degeneration of uterine sympathetic nerves at term pregnancy. Changes in innervation were assessed quantitatively by using computer-assisted methods on uterine cryostat tissue sections stained for tyrosine hydroxylase. At 24 h following treatment of prepubertal rats (25 days of age) with 1 μg or 2.5 μg estrogen, marked increases in uterine size and reductions in the percentage nerve area were observed. Co-administration of DEX (4 mg/kg) attenuated both these short-term estrogen-induced effects. Treatment of 19-day-old rats with a single dose of 25 μg estrogen provoked, at 26 days of age, a 54% reduction in the total nerve area. This reduction was abolished by the co-administration of nine doses of DEX (0.5 mg/kg) at 18–26 days of age. Treatment of rats with the same regime of DEX alone increased the total nerve area by 46% of the control values. Studies of control pregnant rats revealed the unexpected presence of intrauterine nerve fibers at term. Treatment of pregnant rats with six doses of DEX (4 mg/kg) at 16–21 days of age had no effects on the density of uterine sympathetic nerves. These results suggest that DEX has growth-promoting effects on immature uterine sympathetic nerves and may antagonize the degenerative effects elicited by long-term exposure to estrogen. This work was partially supported by PEDECIBA, Universidad de la República, Montevideo, Uruguay. The Third World Academy of Sciences (TWAS) supported the visit of A.I. Frías to the Laboratorio de Biología Celular (IIBCE, Montevideo, Uruguay).     

Effect of long-term alcohol intake on the innervation of the rat myocardium

The myocardium of rats kept on DeCarli and Lieber's liquid diet containing alcohol to 36% of the total calories for 8 weeks were examined with Falck-Hillarp's method for the histologic demonstration of catecholamines. Relative fluorescence intensity of the myocardial cells and nerves was measured with the Zeiss-Fluoval microphotometer. Under the effect of alcohol, density of the noradrenergic innervation (number of visualized nerve fibres) decreases and fluorescence of myocardial cells is intensified. The increased fluorescence of myocardial cells can be eliminated with reserpine. It is assumed that chronic alcohol intake induces continuous catecholamine release from monoaminergic nerve fibres of the heart.     

The role of uterine luminal fluid in uterine contractions, sperm transport and fertility of rats

The role of accumulated intrauterine fluid in rats at oestrus was investigated by experimentally altering the fluid volume in 106 rats. Complete evacuation of uterine fluid or low natural fluid volume did not significantly reduce the number of embryos on Day 10 of pregnancy overall. Transuterine (but not transcervical) sperm transport was reduced by uterine fluid removal, but did not vary significantly with naturally occurring variations in fluid content. Irrespective of fluid content, transuterine sperm transport was, on average, greater in right than left horns. Distensible balloons inserted into the uterus indicated that increasing and decreasing volume increased and decreased respectively myometrial activity at oestrus and dioestrus. Left horns contracted less frequently than did right horns at low volumes. While uterine fluid volume clearly affected uterine contractility and transuterine sperm transport, we were unable to demonstrate a major role of fluid for fertility.     

Effects of infantile/prepubertal chronic estrogen treatment and chemical sympathectomy with guanethidine on developing cholinergic nerves of the rat uterus.

The innervation of the uterus is remarkable in that it exhibits physiological changes in response to altered levels in the circulating levels of sex hormones. Previous studies by our group showed that chronic administration of estrogen to rats during the infantile/prepubertal period provoked, at 28 days of age, an almost complete loss of norepinephrine-labeled sympathetic nerves, similar to that observed in late pregnancy. It is not known, however, whether early exposure to estrogen affects uterine cholinergic nerves. Similarly, it is not known to what extent development and estrogen-induced responses in the uterine cholinergic innervation are affected by the absence of sympathetic nerves. To address this question, in this study we analyzed the effects of infantile/prepubertal chronic estrogen treatment, chronic chemical sympathectomy with guanethidine, and combined sympathectomy and chronic estrogen treatment on developing cholinergic nerves of the rat uterus. Cholinergic nerves were visualized using a combination of acetylcholinesterase histochemistry and the immunohistochemical demonstration of the vesicular acetylcholine transporter (VAChT). After chronic estrogen treatment, a well-developed plexus of cholinergic nerves was observed in the uterus. Quantitative studies showed that chronic exposure to estrogen induced contrasting responses in uterine cholinergic nerves, increasing the density of large and medium-sized nerve bundles and reducing the intercept density of fine fibers providing myometrial and perivascular innervation. Estrogen-induced changes in the uterine cholinergic innervation did not appear to result from the absence/impairment of sympathetic nerves, because sympathectomy did not mimic the effects produced by estrogen. Estrogen-induced responses in parasympathetic nerves are discussed, considering the direct effects of estrogen on neurons and on changes in neuron-target interactions.     

Uterine adrenergic and cholinesterase-positive nerves and myometrial catecholamine concentrations during pregnancy in sheep

Uterine adrenergic and cholinesterase (AChE)-positive innervation of the sheep uterus during anestrus and at 4 stages of pregnancy were examined by histochemical methods. In addition, uterine and cervical myometrium concentrations of norepinephrine (NE) and dopamine (DA) were determined using high-performance liquid chromatography. During anestrus, adrenergic and AChE-positive nerve fibers in the uterine myometrium and endometrium were primarily associated with the vasculature. Innervation of myometrial smooth muscle was almost exclusively by adrenergic fibers. In the endometrium, fibers of both types were observed closely associated with endometrial glands, and adrenergic fibers were observed in the connective tissue beneath the luminal epithelium. Density of uterine innervation decreased by day 65 of pregnancy with an additional decrease by day 105. Myometrial NE concentrations were higher in the cervix than the uterus. Uterine NE concentrations generally were not affected by pregnancy. Although cervical NE per gram of tissue decreased during pregnancy, this effect of pregnancy was not detected when NE was expressed per microgram of DNA. Myometrial DA concentrations were higher in uterine segments than in the cervix. DA concentrations decreased during pregnancy in all tissues except the posterior uterine segment. The DA to NE ratio in the uterus was greater than that for the cervix and was not generally affected by the stage of pregnancy. These results demonstrate that cholinergic and adrenergic nerves supply the sheep uterus. Decreasing fiber density during pregnancy suggests that a majority of the innervation to the sheep uterus is supplied by 'short' nerve fibers whose activity is regulated by steroids of pregnancy. The possible role of DA as a neurotransmitter in the sheep uterus is discussed.     

Transection of the pelvic or vagus nerve forestalls ripening of the cervix and delays birth in rats

Innervation of the cervix is important for normal timing of birth because transection of the pelvic nerve forestalls birth and causes dystocia. To discover whether transection of the parasympathetic innervation of the cervix affects cervical ripening in the process of parturition was the objective of the present study. Rats on Day 16 of pregnancy had the pelvic nerve (PnX) or the vagus nerve (VnX) or both pathways (PnX+VnX) transected, sham-operated (Sham) or nonpregnant rats served as controls. Sections of fixed peripartum cervix were stained for collagen or processed by immunohistochemistry to identify macrophages and nerve fibers. All Sham controls delivered by the morning of Day 22 postbreeding, while births were delayed in more than 75% of neurectomized rats by more than 12 h. Dystocia was evident in more than 25% of the PnX and PnX+VnX rats. Moreover, on prepartum Day 21, serum progesterone was increased severalfold in neurectomized versus Sham rats. Assessments of cell nuclei counts indicated that the cervix of neurectomized rats and Sham controls had become equally hypertrophied compared to the unripe cervix in nonpregnant rats. Collagen content and structure were reduced in the cervix of all pregnant rats, whether neurectomized or Shams, versus that in nonpregnant rats. Stereological analysis of cervix sections found reduced numbers of resident macrophages in prepartum PnX and PnX+VnX rats on Day 21 postbreeding, as well as in VnX rats on Day 22 postbreeding compared to that in Sham controls. Finally, nerve transections blocked the prepartum increase in innervation that occurred in Sham rats on Day 21 postbreeding. These findings indicate that parasympathetic innervation of the cervix mediates local inflammatory processes, withdrawal of progesterone in circulation, and the normal timing of birth. Therefore, pelvic and vagal nerves regulate macrophage immigration and nerve fiber density but may not be involved in final remodeling of the extracellular matrix in the prepartum cervix. These findings support the contention that immigration of immune cells and enhanced innervation are involved in processes that remodel the cervix and time parturition.     

Autonomic innervation of receptors and muscle fibres in cat skeletal muscle

Cat hindlimb muscles, deprived of their somatic innervation, have been examined with fluorescence and electron microscopy and in teased, silver preparations; normal diaphragm muscles have been examined with electron microscopy only. An autonomic innervation was found to be supplied to both intra- and extrafusal muscle fibres. It is not present in all muscle spindles and is not supplied at all to tendon organs. Fluorescence microscopy revealed a noradrenergic innervation distributed to extrafusal muscle fibres and some spindles. On the basis of the vesicle content of varicosities the extrafusal innervation was identified as noradrenergic (32 axons traced), and the spindle innervation as involving noradrenergic, cholinergic and non-adrenergic axons (14 traced). Some of the noradrenergic axons that innervate spindles and extrafusal muscle fibres are branches of axons that also innervate blood vessels. We cannot say whether there are any noradrenergic axons that are exclusively distributed to intra- or extrafusal muscle fibres. The varicosities themselves may be in neuroeffective association with striated muscle fibres only, or with both striated fibres and the smooth muscle cells in the walls of blood vessels. The functional implications of this direct autonomic innervation of muscle spindles and skeletal muscle fibres are discussed and past work on the subject is evaluated.     

Intrinsic innervation of the uterus in guinea pig and rat

The pattern of distribution of cholinergic and adrenergic nerves in the uterus of albino rats and guinea pigs was examined histochemically. In the albino rat, the uterus was found well-innervated by both adrenergic and cholinergic nerves with a clear regional variation. Dense innervation was demonstrated at the tubal and cervical ends of the uterus and in the cervix. Cholinergic nerves supplying the glands were more numerous than the adrenergic nerves which were relatively few. In the guinea-pigs, the uterus was richly innervated by adrenergic nerves with a clear regional variation. No cholinesterase-positive nerves or nerve cells were demonstrated.     

Changes in the density of peripheral benzodiazepine binding sites in genital organs of the female rat during the oestrous cycle

The affinity and the density of peripheral-type benzodiazepine binding sites (PBzS) in tissues from the genital organs of female rats were studied during the oestrous cycle. When comparing PBzS density on the day of oestrus to PBzS density on the day of pro-oestrus, a significant increase was observed in the ovary (1.9-fold), oviduct (2.4-fold) and uterus (1.7-fold), but not in the kidney. Serum oestradiol also increased to a maximum on the day of pro-oestrus. The ovarian and uterine PBzS density and serum concentrations of oestradiol and progesterone were measured every 8 h between the days of dioestrus and pro-oestrus. Ovarian and uterine PBzS density increased to a maximal value at 01:00 and 09:00 h, respectively, on the day of pro-oestrus. However, a significant increase in PBzS density occurred in the ovary (P less than 0.02) and uterus (P less than 0.001) at 09:00 h on the day of pro-oestrus as compared to 09:00 h on the day of dioestrus. These changes were associated with an increase in serum oestradiol and progesterone concentrations. The affinity of PBzS in all tissues examined remained unaltered during the oestrous cycle. This study demonstrates that changes associated with the oestrous cycle occur in the density of PBzS in various genital organs.     

Characterization of fibroblastic cell plasticity in the lamina propria of the rat uterine cervix at term

Different organs contain fibroblasts with specific features and functions, indicating the complexity of fibroblast biology. In the rat cervical stroma, fibroblasts are preferentially located in the fibrous ring that surrounds the mucous layer. The purpose of this study was to investigate the morphological features and immunophenotype of fibroblastic cells of the uterine cervix in cycling, pregnant, and postpartum rats. Expression of the cytoskeletal proteins desmin, vimentin, and alpha-smooth muscle actin (alpha-SMA) were studied by immunohistochemistry. The optical density of immunohistochemical staining was quantified by image analysis. The ultrastructural features of fibroblastic cells were observed under transmission electron microscopy. Cervical fibroblastic cells always expressed vimentin and desmin but never alpha-SMA. During the first half of pregnancy (Day 5 [D5] to D14), desmin intensity values were similar to those of cycling and postpartum fibroblasts. In contrast, a strong expression of desmin was found from D15 to D22, with maximal expression at term (D23). Immunohistochemical expression for vimentin was constant throughout pregnancy and showed no differences with cycling and postpartum uterine cervices. Stromal cells from cycling and early pregnant rats displayed ultrastructural features characteristic of typical fibroblasts. In contrast, at the end of pregnancy, fibroblasts differentiated and showed increased secretory characteristics, reaching the ultrastructural features of a myofibroblast. Based on the differential expression of desmin and the electron microscopic observations, the foregoing results showed a modulation of the fibroblastic phenotype in the uterine cervix during pregnancy. To our knowledge, this is the first report that addresses the presence of myofibroblasts derived from resident fibroblasts in the fibrous ring of the rat uterine cervix. Fibroblastic-myofibroblastic cell plasticity may have implications in the physiological changes displayed in the uterine cervix during pregnancy, parturition, and postpartum involution.     

Comparative distribution of neuropeptide tyrosine-,vasoactive intestinal polypeptide-, substance P-immunoreactive,acetylcholinesterase-positive and noradrenergic nerves in the reproductive tract of the female rat

Summary Location, distribution and density of nerve fibers immunoreactive to neuropeptide tyrosine, vasoactive intestinal polypeptide and substance P were studied in the reproductive tract of the female rat and compared with acetylcholinesterase-positive (cholinergic) and noradrenergic nerves. Plexuses of all types of fibers were present in the vagina, uterine cervix, uterine horn and oviduct. In the tubular reproductive organs all of these types of nerve fibers appeared to innervate vascular and non-vascular smooth muscle and nearly all types of fibers formed plexuses subjacent to the epithelium lining the organs. Individual fibers of all classes appeared to innervate fascicles of smooth muscle in the mesometrium of the uterine horn. A few acetylcholinesterase-positive and substance P-immunoreactive fibers were present in the ovary but no vasoactive intestinal polypeptide-immunoreactive nerves were observed. Noradrenergic and neuropeptide tyrosine-immunoreactive nerves were numerous in the ovary where they were seen in the interstitial gland tissue and associated with follicles and blood vessels. It is suggested that these nerves may influence hemodynamic events and non-vascular smooth muscle in such functions as transport of sperm and ova and parturition. Substance P-immunoreactive nerve fibers are likely to be sensory fibers that could have roles in neurohormonal reflexes.