2.45-GHz microwave irradiation adversely affects reproductive function in male mouse, Mus musculus by inducing oxidative and nitrosative stress.

Electromagnetic radiations are reported to produce long-term and short-term biological effects, which are of great concern to human health due to increasing use of devices emitting EMR especially microwave (MW) radiation in our daily life. In view of the unavoidable use of MW emitting devices (microwaves oven, mobile phones, Wi-Fi, etc.) and their harmful effects on biological system, it was thought worthwhile to investigate the long-term effects of low-level MW irradiation on the reproductive function of male Swiss strain mice and its mechanism of action. Twelve-week-old mice were exposed to non-thermal low-level 2.45-GHz MW radiation (CW for 2 h/day for 30 days, power density = 0.029812 mW/cm(2) and SAR = 0.018 W/Kg). Sperm count and sperm viability test were done as well as vital organs were processed to study different stress parameters. Plasma was used for testosterone and testis for 3ß HSD assay. Immunohistochemistry of 3ß HSD and nitric oxide synthase (i-NOS) was also performed in testis. We observed that MW irradiation induced a significant decrease in sperm count and sperm viability along with the decrease in seminiferous tubule diameter and degeneration of seminiferous tubules. Reduction in testicular 3ß HSD activity and plasma testosterone levels was also noted in the exposed group of mice. Increased expression of testicular i-NOS was observed in the MW-irradiated group of mice. Further, these adverse reproductive effects suggest that chronic exposure to nonionizing MW radiation may lead to infertility via free radical species-mediated pathway.

Four Hour Temporal Relation of 5-HTP and L-DOPA Induces Inhibitory Responses in Recrudescing Gonad of Indian Palm Squirrel (Funambulus pennantii).

Daily injections of L-dihydroxyphenylalanine (L-DOPA, dopamine precursor) given 4 h after 5-hydroxytryptophan (5-HTP, serotonin precursor) induced inhibitory responses in recrudescing gonad (in the first week of December) of Indian palm squirrel, a seasonally breeding subtropical animal. Other temporal relations (L-DOPA given at 0, 8, 12, 16, and 20 h after 5-HTP administration) did not show any effect on the recrudescing gonad. This inhibitory effect of 4 h was evident under short day length (6 : 18) group but was masked by the increasing day length of nature (NDL, late December onwards) and increased photoperiod of long day group (16 : 8). It is apparent that seasonal testicular recrudescence of Indian palm squirrel during short day length by 4 h relation of 5-HTP and L-DOPA is not a pharmacological effect but actually is an alteration of seasonality in this annually breeding mammal. It seems that endogenous mechanism controlling seasonal testicular recrudescence of Indian palm squirrel is reset by timed daily injections of these neurotransmitter drugs. It is suggested that in spite of different environmental factors (photoperiod, humidity, etc.) used by different species to time their annual reproduction, basic mechanism of seasonality appears to be the same, that is, the temporal synergism of neurotransmitter activity.

Tissue localization of collagenase and leucine aminopeptidase in the bovine filarial parasite Setaria cervi.

BACKGROUND: Like other helminth proteases, filarial proteases have also been shown to require for parasite survival inside the host and mediate various physiologic processes such as tissue invasion, feeding, embryogenesis and host immune evasion. Many of these proteases have shown potential for vaccines and chemotherapeutic agents against active filarial infections. Setaria cervi is a bovine filarial parasite and serves as a good parasite model for the studies in lymphatic filariasis. Recently, a 175 kDa collagenase and leucine aminopeptidase (LAP) have been purified and characterized from the bovine filarial parasite S. cervi and shown to be potential vaccine candidate and diagnostic marker, respectively for human lymphatic filariasis. However, their tissue localizations and putative roles in the parasite biology have not yet been examined and thus remain unclear. Therefore, the current study attempts to localize and explore the putative roles of these two enzymes in S. cervi. METHODS: The tissue distributions of 175 kDa collagenase and leucine aminopeptidase in S. cervi were examined by immunohistochemical and histochemical methods, respectively. Immune sera obtained from the jirds immunized with collagenase served as primary antibody, rabbit anti-mouse IgG-HRP conjugate as secondary antibody and DAB as the substrate for the immunostaining of collagenase. Leu-betaNA was used as the substrate for the histochemical staining of LAP. RESULTS: Both the collagenase and LAP were present in the body wall; however, they differ in their distribution pattern in different layers of body wall. Collagenase was mainly localized in epicuticle, cuticle, syncytial hypodermis and the nerve cord region whereas LAP was more concentrated in epicuticle, longitudinal muscle layers and almost absent or very faintly stained in syncytial hypodermis and nerve cord region. Both collagenase and LAP showed their common distributions in intestine, uterus and mature eggs, growing embryos and mf. Very strong immunostaining of collagenase in the outer body surface of the parasite indicates its major role in host-parasite relationship whereas the presence of LAP in muscular region suggests its role in tissue remodeling. The common presences of collagenase and LAP in the S. cervi intestine, ovary, uterus, eggs and mf suggest that they also have collaborative roles in molting, nutrition and embryogenesis. The data obtained on their immunological characterizations and their presence in important parasite organs give strong indication that they are critical for the survival of filarial parasite and thus can be good vaccine candidates and/or diagnostic markers for human lymphatic filariasis. CONCLUSION: The manuscript reports for the first time the tissue distribution of collagenase and LAP in the bovine filarial parasite S. cervi and discuss their putative roles in vivo. Our findings also open the avenue to examine the roles of these two proteases in vivo, which will require further experiments like using their natural substrates and/or specific inhibitors in each tissues.

Effect of temporal synergism of neural oscillations on photorefractoriness in Japanese quail (Coturnix coturnix japonica).

Circadian rhythms in many metabolic functions including neural (transmitters) and hormonal secretion appear to change with physiological condition. It is also reported that seasonal changes in photoperiodism/reproduction and other metabolic conditions may result from a temporal interaction of circadian neural oscillations that change seasonally. To test this hypothesis, the present study was designed to study the effect of temporal synergism of two neural oscillations (serotonin and dopamine) on relative photorefractoriness of Japanese quail. Serotonin and dopamine precursor drugs (5-HTP, 5-hydroxytryptophan and L-DOPA, L-dihydroxyphenylalanine) were administered (intraperitonially 5 mg/100 g body weight) at six different time intervals of 0, 4, 8, 12, 16 and 20 hr in sexually mature quail (>12 weeks old). The birds of control group received two daily injections of normal saline. The treatment was given for 13 days in continuous condition of light and then the quail were shifted to intermediate daylength (LD 13.5:10.5 for experiment 1) and short daylength (LD 8:16 for experiment 2). Six weeks following treatment, birds in intermediate daylength showed regressed cloacal gland and testicular activity except in 12-hr group, which exhibited gonadostimulatory condition. But birds of all the groups in short daylength showed complete regression of cloacal gland after 4 weeks of the treatment. In experiment 3, reproductively quiescent relative photorefractory quail maintained under intermediate daylength (LD 13.5:10.5) received 13 daily injections of 5-HTP and L-DOPA at the interval of 12 hr. At 6 weeks post-treatment, it was observed that unlike cloacal gland of control quail, which remained regressed, that of 12-hr quail showed significant development. These findings indicate that 12-hr temporal interaction of 5-HTP and L-DOPA administration maintained reproductive system in stimulated condition and prevented reproductive regression in photorefractory quail, but did not prevent the onset of scotosensitivity. It is concluded that the 12-hr temporal relationship of circadian serotonergic and dopaminergic oscillations not only eliminates photorefractoriness but may also re-establish photosensitivity in relative photorefractory quail. These findings suggest the regulatory role of neural oscillations and their temporal interaction in the regulation of neuroendocrine-gonadal axis with special reference to photosensitivity/refractoriness.

Expression of hypothalamic arginine vasotocin gene in response to water deprivation and sex steroid administration in female Japanese quail.

Arginine vasotocin (AVT) is a neurohypophyseal hormone involved in reproductive function and control of osmoregulation in birds. In view of the dual function of AVT, the present experiment was designed to observe the effect of water deprivation (WD) and sex steroid [estradiol benzoate (EB) and testosterone propionate (TP)] treatment independently, as well as simultaneously, on the profile/activity of the hypothalamic AVT system. WD resulted in a significant increase in plasma osmolality, sodium ion concentration and AVT concentration, but administration of sex steroids had no significant influence on these parameters. By contrast, the amount of hypothalamic AVT transcript (northern analysis) and the size of immunoreactive vasotocin (ir-AVT) neurons and hybridization signals (in the form of silver grains), representing AVT mRNA in corresponding neurons of paraventricular nuclei (PVN), increased significantly in all the treated groups compared with controls. Our findings indicate that although sex steroid administration has no effect on plasma osmolality and AVT concentration, unlike water deprivation, it may stimulate the profile/activity of AVT neurons of PVN, supporting the possibility of sex steroid receptors on these neurons. It is concluded that in quail, osmotic stress not only upregulates the expression of the AVT gene in existing neurons but also recruits many more neurons to increase the rate of AVT synthesis and secretion, while sex steroids appear to have a stimulatory effect only on the existing number of neurons and only at the level of transcription/translation and hence may influence/modulate hypothalamic AVT gene expression in response to osmotic stress. This study also suggests an interrelationship between reproduction and AVT system/function in birds.

Changes in expression of AVT and AVT receptor (VT1) gene in hypothalamus and shell gland in relation to egg laying in white leghorn hen.

Oviposition is a complex phenomenon involving various regulatory mechanisms at the neuroendocrine levels. Present study was designed to access the changes in arginine vasotocin (AVT) and its receptor (VT1) gene expression in relation to the time of egg laying of white leghorn hen. The expression of AVT gene (Northern blot analysis and in situ hybridization) in the hypothalamus and localization of ir-AVT in the magnocellular neurons of paraventricular nuclei was studied 2 h before (-2 h), immediately after (0 h) and 2 h after (+2 h) egg laying. Simultaneous changes in the AVT and VT1 receptor gene in the shell gland, which finally responds to AVT for smooth muscle contraction and expulsion of egg, were also determined by semi-quantitative reverse transcriptase-polymerase chain reaction. The findings indicated increased hypothalamic AVT gene expression immediately after egg laying (0 h) when compared to 2 h before and 2 h after egg laying. AVT receptor gene expression in the shell gland also followed the same pattern. However, AVT gene expression in the shell gland, unlike that of hypothalamus was higher at -2 h compared to 0 and +2 h of oviposition. While highly significant increase was noted in plasma AVT concentration at the time of egg laying, other parameters such as plasma osmolality and ionic concentration (Na(+), K(+), Ca(2+), and Cl(-)) did not show any change. It is suggested that in addition to increased hypothalamic AVT transcript and peripheral release, local synthesis of AVT in the shell gland (paracrine release) may contribute to the contraction of shell gland smooth muscles during egg laying. Moreover, these findings clearly indicate temporal correlation of AVT and its receptor gene expression in different tissues during oviposition.

Involvement of adrenal and thyroid activity in the annual testicular regression of red headed bunting (Emberiza bruniceps).

Thyroid and adrenal activities are closely associated with reproductive cycle and any alteration in these endocrine functions may cause changes in the pituitary-gonadal axis. To understand this interrelationship during testicular senstive phase (month of April) male birds were injected with metapyrone(corticosterone synthesis blocks 1 microg/bird/day & 10 microg/bird/day) and newmercazol (thyroxine synthesis blocks 10 microg/bird/day) over a period of 12 weeks. During late breeding phase (month of August) two sets of birds having large gonad (photosensitive) and regressed gonad (photorefractory) were injected with metapyrone (10 microg/bird/alternate day). Results indicate that decreased activity of both adrenal and thyroid, extended the breeding phase but rate of regression decreased only in the case of bird receiving higher level of metapyrone.However,in the second group rate of gonadal regression was slow only in those bird where treatment was started during photosensitive phase. It may be suggested that optimum level of activity of adrenal and thyroid function are essential for termination of reproduction and any alteration in these function may alter seasonal pattern of neuroendocrine gonadal axis.

Water deprivation and circadian changes in plasma arginine vasotocin and mesotocin in the domestic hen (Gallus domesticus).

Possible circadian variations in plasma levels of arginine vasotocin (AVT) and mesotocin (MT) were assessed in domestic hens (Gallus domesticus) under a 12h:12h light-dark (LD) schedule. Blood samples were taken at 4h intervals, and neurohypophyseal hormone levels were determined by radioimmunoassay. Marked circadian changes in both AVT and MT were observed in hens provided free access to water. Minimal and maximal AVT levels occurred at 08:00 and 20:00, respectively. Minimal MT levels occurred at 20:00, whereas maximal MT levels occurred over a broad time period of 04:00 to 12:00. In water-deprived hens, plasma AVT levels were elevated at each time point, and the circadian variations in plasma AVT and MT levels were attenuated. These results demonstrate that rhythmicity in neurohypophyseal function in a lower vertebrate species, like that in mammals, is disrupted by osmotic stress.

A sexual dimorphism in hypothalamic arginine vasotocin (AVT) gene expression and AVT plasma levels in the Japanese quail (Coturnix coturnix japonica) in response to water deprivation.

To examine a possible sexual dimorphism in the osmotic control of arginine vasotocin (AVT) release in birds, age-matched male and female Japanese quail were subjected to water deprivation. The observed increased plasma osmolalities were accompanied by increased plasma AVT levels. Plasma mesotocin levels did not change with water deprivation. The sensitivity of the osmotic control of AVT release as determined by the slope of the relationship between plasma AVT levels and plasma osmolalities was significantly (P < 0.05) higher in males than in females. By Northern blot analysis, levels of hypothalamic AVT gene transcripts were increased 2.3 +/- 0.14- and 3.5 +/- 0.13-fold in water-deprived male and female Japanese quail, respectively, compared to normally hydrated birds. Our data suggest gender-related differences in the osmotic control of AVT release and in hypothalamic AVT gene expression in the Japanese quail.

Effect of gonadotrophin and sex steroid on the scotoresponses of day old chicks of Japanese quail, Coturnix coturnix japonica.

Luteinizing hormone (LH) and testosterone propionate (TP) were tested for their effects on the development of scotorefractoriness in Japanese quail. Day old chicks of both the sexes were divided into four groups and treated with normal saline, LH (1 microg/100 g body weight) and two doses of TP (100 microg/100 g body weight- TP1 and 1 mg/100 gm body weight- TP2) over a periods of 14 weeks. In the male chicks, compared to control, LH treatment advanced and low dose of TP suppressed the development of scotorefractoriness, while high dose of TP inhibited it completely and maintained the birds in scotosensitive state. On the other hand, in females, LH treatment increased the rate of sexual development resulting in the onset of egg laying earlier than that of control, but both the doses of steroid hormone suppressed ovarian development. It is suggested that, LH treatment not only induced a higher degree of reproductive development in short day quail but may also advance sexual maturity as under long daylength. Further, both the doses of male hormone had negative feedback effect on neuroendocrine axis and eliminated the attainment of scotorefractoriness i.e., reproductive development under short days.

Arginine vasotocin gene expression in hypothalamic neurons is up-regulated in chickens drinking hypertonic saline: an in situ hybridization study.

Osmotic stress stimulates the release of the avian hypothalamic neuropeptide arginine vasotocin (AVT) into the peripheral circulation. We conducted the present study to investigate the effects of salt-loading on AVT secretion and AVT gene expression in specific hypothalamic nuclei in chickens. White Leghorn chickens were provided food ad lib and either water or 2% NaCl to drink. Both plasma osmolality and plasma AVT levels were significantly increased in chickens that drank 2% NaCl for either two or four days compared to that in chickens that drank water. Results from in situ hybridization analysis demonstrated an increase in the number of neurons expressing AVT mRNA in the supraoptic (SON) and paraventricular nuclei (PVN) in chickens provided 2% NaCl to drink compared to chickens that were provided water to drink. The number of grains per neuron increased in the PVN, but not in the SON of osmotically stimulated birds. Thus, increased osmolality resulting from ingestion of hypertonic saline is an effective stimulus to increase hypothalamic AVT mRNA content in chickens.

Changes in poly(A) tail length of arginine vasotocin messenger ribonucleic acid in the hypothalamus of water-deprived chickens.

The effects of water deprivation on the secretion of vasotocin (AVT) and expression of the AVT gene were studied in White Leghorn cockerels. Animals deprived of water for 4 days were compared with normally hydrated controls. Blood samples were obtained for measurements of plasma osmolality and AVT levels, and the hypothalamus was collected for extraction of total cellular RNA. A 519-bp AVT cDNA was prepared by reverse transcriptase-polymerase chain reaction and a 209-bp PstI/EcoRI restriction fragment from the 3' region of the fowl AVT cDNA was used as a probe for Northern blot analysis. Plasma osmolality and AVT levels in dehydrated birds were about 30 and 350% greater, respectively, than those in normally hydrated controls. The quantity of hypothalamic AVT mRNA was 2. 3-fold greater in water-deprived birds compared to controls. The size of the hypothalamic AVT transcript was about 100-bp longer in the water-deprived birds. As determined by RNase H treatment in the presence and absence of oligo(dT)12-18, the increase in mean size of the AVT mRNA in dehydrated animals was due to a longer poly(A) tract. Our results indicate that osmotic stress up-regulates expression of the AVT gene and increases the accumulation of AVT mRNA in the hypothalamus. This accumulation may, in part, be due to lengthening of the AVT mRNA poly(A) tail which is a general mechanism associated with stabilization of vertebrate mRNAs.

Functional maturation of neuroendocrine gonadal axis is altered by specific phase relations of circadian neurotransmitter activity in Japanese quail.

The present study was designed to ascertain the effects of temporal relationship of circadian neural oscillations on puberty attainment and reproductive growth of Japanese Quail, Coturnix coturnix japonica. Serotonin and dopamine precursors (5-hydroxytryptophan, 5-HTP and L-dihydroxyphenylalanine, L-DOPA; 5 mg/100 g body weight) were injected daily, 8 and 12 h apart in two groups of one-day old chicks, while controls received two daily injections of normal saline. Weekly/biweekly observations (body weight, cloacal gland size, testicular volume and activity, ovarian follicular diameter and rate of egg production) were made until 9 weeks of age, when the experiment was terminated. Results indicate that 8 h relationship completely suppressed gonadal growth even under long photoperiod (LD 16:8), while a 12 h relationship induced precocious sexual maturity and increased the rate of reproduction (spermatogenesis and egg production). It is concluded that circadian phase relationship of serotonergic and dopaminergic activity may not only determine the onset of reproduction in this poultry species, but may also alter the rate of reproduction possibly by affecting photoperiodic mechanism of reproductive regulation.

Effect of photoperiod in the regulation of the annual testicular cycle of a subtropical mammal, the Indian palm squirrel, Funambulus pennanti.

In seasonally breeding subtropical mammal, the Indian palm squirrel (Funambulus pennanti), reproductive recrudescence is initiated before the winter solstice followed by sexually active condition which extends until the end of summer season. Onset of seasonal regression coincides with the annual decrease in daily photoperiod and the increased level of relative humidity resulting from the arrival of monsoon at this latitude. To test the photoperiodic responses, three groups of squirrels were exposed to natural day length (NDL), long day length (LD 15:9), and short day length (LD 6:18) over a period of one year beginning from March. Squirrels of all these groups were exposed to similar ambient temperature and humidity conditions. Initially, the rate of testicular development was similar in control and long day squirrels attaining peak values in May (0.67 cm3) and June (0.7 cm3) respectively. Thereafter, while the gonads of controls regressed, the latter maintained a plateau. On the other hand, the gonads of short day squirrels regressed sharply until June (0.21 cm3) followed by spontaneous recrudescence and finally a plateau (0.55 cm3). These results indicate that initially squirrels are photosensitive (as long days are gonadostimulatory and short days are inhibitory) in the first half of summer season but eventually become refractory to the inhibitory effect of short days. Obviously, an acyclic condition is developed under constant long as well short day conditions maintaining the neuroendocrine-gonadal-axis in a continuously active state. We suggest that in nature although gonadal growth of this species does not synchronize with the increase in daily photoperiod, it is partially regulated by an interplay of annual photocycle and humidity conditions.(ABSTRACT TRUNCATED AT 250 WORDS)

Arginine vasotocin gene expression in neuroendocrine, reproductive and gastrointestinal tissues of the domestic fowl: detection by reverse transcriptase polymerase chain reaction.

Arginine vasotocin gene transcripts in various tissues of the domestic fowl were detected by reverse transcriptase polymerase chain reaction followed by Southern blot analysis using a 209 bp fragment from the 3'-region of a cDNA encoding chicken arginine vasotocin as the probe. Relatively strong signals were observed with hypothalamic, adenohypophysial and proventricular RNA as the starting material. Lesser signals were obtained from RNA isolated from shell gland, adrenal gland, post-ovulatory follicles and ovarian thecal cells. Arginine vasotocin gene transcripts were undetectable in the posterior pituitary gland, small intestine and large intestine. These results suggest that in addition to its well-known antidiuretic and oxytocic actions, arginine vasotocin may act as a local neuromodulator or mediator and have other important autocrine or paracrine actions in non-hypothalamic tissues.

An in situ hybridization and immunohistochemical study of vasotocin neurons in the hypothalamus of water-deprived chickens.

The distribution of immunoreactive vasotocin (IR-AVT) and AVT mRNA in the hypothalamus of White Leghorn cocks was determined by immunohistochemistry and in situ hybridization, respectively. In control birds that were provided with water ad lib, AVT mRNA was distributed in the periventricular and lateral regions of the hypothalamus in clusters of neurons that correspond structurally with the mammalian paraventricular (PVN) and supraoptic (SON) nuclei. Although the distribution of AVT, identified by immunohistochemistry of adjacent serial sections within the hypothalamus, was similar to the distribution of AVT mRNA, the possibility that some positive staining was due to mesotocin neurons was not excluded. Water deprivation for 2 and 4 days resulted in both an increase in levels of AVT mRNA per neuron and the number of AVT mRNA-containing cells. Additionally, water deprivation resulted in a decrease in the amount of IR-AVT per neuron. The results indicate that osmotic stimulation increases AVT gene expression not only in individual neurons but also by activating subpopulation of neurons that are not observed in normally hydrated birds.

Photoperiodism in Japanese quail (Coturnix coturnix japonica) with special reference to relative refractoriness.

Cloacal gland (an androgen dependent sex accessory) of Japanese quail exhibits full breeding condition as long as these were maintained under long days (LD 16:8). When shifted to short daylength (LD 6:18), scotosensitivity (cloacal gland regression) was observed up to 5 weeks, followed by scotorefractoriness (cloacal gland development). There was a regression in cloacal gland volume of the birds when shifted to intermediate daylength (LD 13.5:10.5 and 13:11) after 12 weeks of exposure to long days (relative refractoriness) but no regression when shifted to relatively short days (< 14 hr) after 3 weeks of exposure to long daylength. Birds maintained under constant short photoperiod (LD 6:18) exhibited cyclicity. Shift experiments (quail reared and maintained under continuous light; LL, were shifted to LD 16:8, 13:11 and 8:16, similarly quail maintained under LD 16:8 were shifted to rest three photoperiods and so on) made to compare the cloacal gland responses indicated that if the difference between two photoperiods (previous and shifted one) was more the percentage of difference in cloacal gland response was also high. Short daylength (LD 8:16) was always gonadoinhibitory for the quail previously exposed to any daylength (13L, 16L or 24L) and 16L and 24L were always stimulatory for the quail previously exposed to other daylength (8L, 13L, 16L). But, when the birds were shifted to 13L, photoresponses cannot be generalized and it depends on the photoperiod to which quail were exposed previously (i.e. photoperiodic history).

Influence of different photoperiods on development of gonad, cloacal gland and circulating thyroid hormones in male Japanese quail Coturnix coturnix japonica.

One day old chicks of Japanese quail were exposed to different photoperiods (LD, 8:16, 13.5:10.5, 16:8 and LL) and observations (testes weight, cloacal gland size, body weight and circulating thyroxine and triiodothyronine) were taken at the age of 3, 5, 7, 9 and 16 weeks. Results indicate that immediate reproductive development occurred in birds exposed to long photoperiods (greater than 12 hr). Growth under LD 8:16, was not apparent till 7th week and by 16 weeks, degree of gonadal development was similar in all the birds, irrespective of photoperiodic treatment. Whereas body weight of the intermediate and long day (LD 13.5:10.5, 16:8 and LL) treated birds increased upto 5th week and remained constant thereafter. But the chicks maintained under short day length (LD 8:16), showed spontaneous increase till the end of the study and birds were much heavier compared to all other groups. Plasma T4 concentration increased with increasing age till 9th week and remained unaltered thereafter. On the other hand T3 level did not change till 7th week followed by a decline. It is suggested that the initiation and degree of gonadal growth in quail depends on the availability of daily photoperiod, until the achievement of full breeding condition. Peak level of T4 observed in 9 week old birds may be involved in the development of photorefractoriness at that age.

The effects of daily injections of L-dihydroxyphenylalanine and 5-hydroxytryptophan in different temporal relationships on thyroid-gonadal interaction in an Indian finch, spotted munia, Lonchura punctulata.

Daily injection of L-dihydroxyphenylalanine (L-DOPA, a dopamine precursor) given 12 hr after 5-hydroxytryptophan (5-HTP, a serotonin precursor) stimulated testicular growth and body weight increase in the spotted munia Lonchura punctulata. Daily injections of the same drugs given 8 hr apart had the opposite effect, inhibiting both testicular growth and body weight gain. These responses were not observed when either of the drugs were given alone, indicating that the effect was due to temporal synergism between serotonergic and dopaminergic functions. The inhibitory effect of daily injections of thyroxine on testicular and body growth were negated by injections of 5-HTP and L-DOPA separated by 12 hr. Conversely, the stimulatory effects of thyroidectomy in maintaining full testicular size and body weight after the breeding seasons were negated by daily injections of 5-HTP and L-DOPA separated by 8 hr. It is concluded that the inverse relationship between seasonal changes in thyroidal and reproductive functions may involve seasonal changes in phase relationships between daily rhythm in serotonergic and dopaminergic activity in the central nervous system.

Suppression of annual testicular development in Indian Palm squirrel, Funambulus pennanti by 8 hr temporal relationship of serotonin and dopamine precursor drugs.

Daily injections of 5-HTP (5-hydroxytryptophan, serotonin precursor) and L-DOPA (L-Dihydroxyphenylalanine, dopamine precursor) given 8 hour apart inhibited normal testicular growth in seasonally breeding Indian Palm Squirrel, Funambulus pennanti leading to complete gonadal atrophy, which was maintained till the end of the study. HCG administration induced higher degree of gonadal development but, when the two treatments (HCG + 8 hr relationship of 5-HTP and L-DOPA) were given simultaneously no significant difference was observed compared to control. Results indicate that induced suppression of gonadal function in a fashion similar to seasonal regression leading to non-breeding condition is the consequence of specific phase relationship (8 hr) between serotonergic and dopaminergic activities and not due to Serotonin or dopamine alone. This suggestion gets support from the finding that gonadal condition of squirrels receiving only 5-HTP (5-HTP control) or L-DOPA (DOPA control) was not different from control and exhibited normal testicular growth. It also seems that neurotransmitter precursor drugs given 8 hr apart possibly inhibited the activity of neuroendocrine-gonadal axis since this effect was overpowered by stimulatory effect of gonadotrophin. The findings strongly support the hypothesis that specific phase relation of circadian serotonergic and dopaminergic oscillations account for seasonal reproductive conditions.