Elsevier

Zoology

Volume 112, Issue 6, November 2009, Pages 461-470
Zoology

Temporal synergism of neurotransmitters (serotonin and dopamine) affects testicular development in mice

https://doi.org/10.1016/j.zool.2009.03.002Get rights and content

Abstract

The temporal phase relation of circadian oscillations is reported to regulate reproduction in many seasonally breeding avian and mammalian species, but its role in the reproductive regulation of continuous breeders is not yet known. Hence in the present study, six experimental groups of 3-week-old male Parkes strain mice, Mus musculus, were injected with 5-hydroxytryptophan (5-HTP, serotonin precursor) and l-dihydroxyphenylalanine (l-DOPA, dopamine precursor) at intervals of 0, 4, 8, 12, 16 or 20 hr (5 mg/100 g body weight per day for 13 days). Control mice received two daily injections of normal saline. When observed 24 days post-treatment, 8-hr mice exhibited low body weight and suppression of gonadal activity (spermatogenesis, sperm count/motility/viability and plasma testosterone concentration), while body weight and degree of gonadal development were higher in the 12-hr mice as compared to the controls. It is concluded that normal somatic and gonadal growth of pre-puberal mice may be suppressed with an 8-hr phase relation of circadian serotonergic and dopaminergic oscillations. On the other hand, a 12-hr phase relation accelerated the rate of gonadal maturation, while other relations led to more or less similar gonadal development as in the control mice. This study suggests the importance of circadian organization as a function of specific temporal phase relations of neural oscillations in the maturation of gonads. Although the exact mechanism still needs to be investigated, this seems to be mediated via effects on the neuroendocrine axis.

Introduction

In seasonally breeding vertebrates, gonadal development and associated breeding activities are controlled by environmental cues such as photoperiod and temperature. Changes in the daily photoperiod (day length) registered by the organism is the most common trigger of the annual gonadal development and regression, suggesting that the circannual organization receives input from the circadian organization. The photic information is transmitted to the endocrine system via the hypothalamo–hypophyseal–gonadal axis. In mammals, the suprachiasmatic nuclei (SCN) play a central role in the circadian system. Other areas like the pineal gland may also be involved since rhythmicity is not completely eliminated following bilateral lesions of the SCN (Moore-Ede, 1983; Moore et al., 1995). Significant circadian rhythms of hypothalamic serotonin and dopamine concentrations have been observed in the SCN of hamsters, which had a 12- to 16-hr phase relationship in the scotorefractory and a 0- to 4-hr phase relation in the scotosensitive condition (Wilson and Meier, 1987).

The pioneer study by Meier's group on the white-throated sparrow hypothesized that endogenous seasonality, which determines photosensitivity and photorefractoriness, involves the temporal interaction of two circadian neural oscillations (Miller and Meier, 1983a, Miller and Meier, 1983b). The experimental basis of this hypothesis was that hormone activity, e.g. of corticosterone and prolactin, differs as a function of the time of the day and that the phase of these circadian hormonal rhythms changes seasonally. Based on the evidence that hormonal rhythms are the expression of neural rhythms, in later experiments 5-hydroxytryptophan (5-HTP), a rate-limiting precursor substrate for serotonin, was substituted for corticosterone, and L-dihydroxyphenylalanine (l-DOPA), a rate-limiting precursor for dopamine, was substituted for prolactin. In fact, the circadian rhythms of some hormones, such as corticosterone and prolactin, appear to be an important expression of these (serotonergic and dopaminergic) oscillations and by feedback mechanisms hormonal rhythms may not only maintain the neural oscillations but may also entrain each other (Meier et al., 1971).

According to mammalian literature, brain serotonergic activity influences adrenal corticosteroid secretion, and parachlorophenylalanine (PCPA), which blocks the synthesis of serotonin, dampens the plasma corticosteroid rhythm (Scapagnini et al., 1971; Balestrery and Moberg, 1973; Owasoyo and Walker, 1980). Systemic 5-HTP and intraventricular 5-hydroxytryptamine (5-HT, i.e. serotonin) cause a rise in plasma corticosteroid concentration (Popova et al., 1972), which in turn exerts a feedback effect on the synthesis of brain 5-HT (Telegdy and Vermes, 1975; Sze et al., 1976). This effect results from stimulation of brain tryptophan hydroxylase activity which catalyzes the conversion of tryptophan to 5-HT. Thus, circadian variation may affect many systems and oscillations including hormonal and neural systems with different time courses. And circadian variation in different endocrine or neural activities may be correlated with seasonal variation in physiological functions. In this context, Wilson and Meier (1989) reported a resetting of the annual cycle (scotorefractory and scotosensitive conditions) in the Syrian hamster with timed daily injections of 5-HTP and l-DOPA.

This hypothesis was further confirmed by many reports from our laboratory on different species of seasonally breeding birds, namely the red-headed bunting, Emberiza bruniceps (Chaturvedi and Bhatt, 1990), the Japanese quail, Coturnix coturnix japonica (Phillips and Chaturvedi, 1995), the spotted munia, Lonchura punctulata (Prasad and Chaturvedi, 1998), the lal munia, Estrilda amandava (Chaturvedi et al., 1994) and one species of mammal, the Indian palm squirrel, Funambulus pennanti (Chaturvedi and Jaiwal, 1990; Jaiwal and Chaturvedi, 1991; Chaturvedi and Singh, 1992). All these findings suggest that the temporal phase relation of circadian neural oscillations may induce specific reproductive/metabolic conditions in seasonal breeders. A number of studies on Japanese quail (which breeds continuously if maintained under constant day length and shows a seasonal gonadal cycle if maintained under natural day length; Chaturvedi et al., 1993) also indicate a regulatory role of circadian organization (specific phase relation of circadian neural oscillations) in the functional maturation of the neuroendocrine–gonadal axis and puberty attainment (Phillips and Chaturvedi, 1995), during photosexual responses (Chaturvedi et al., 1991) including photorefractoriness (Chaturvedi et al., 2006) and in fertility/egg production (Tiwari and Chaturvedi, 2003). This treatment (5-HTP and l-DOPA given at specific time intervals), in addition to modulating the gonadal activity, is also reported to alter the phase relation of the circadian hypothalamic content of serotonin and dopamine in the quail (8-hr and 12-hr intervals; Kumar et al., 2009). Interestingly, circadian variation in the hypothalamic serotonin and dopamine content also exhibits different phase relations in the breeding and non-breeding quail (Tiwari et al., 2006).

However, it is not known if this mechanism may also be effective in a continuous breeder, especially during maturation of the gonadal axis. Hence, the present study was designed to address the putative regulatory role of circadian oscillations in the reproductive development of laboratory mice. The aim of the study was to investigate if normal gonadal development in pre-puberal mice may be altered as a function of the specific phase relation of neurotransmitter precursors that are reported to regulate seasonal physiological and behavioral changes in relation to reproduction injected at different time intervals.

Section snippets

Animals

Male laboratory mice (Mus musculus) of the Parkes (P) strain were obtained from a colony maintained in our laboratory. The mice were housed under hygienic conditions in a well-ventilated, photoperiodically controlled room (LD 12:12) and were provided with commercial food (Pashu Aahar Kendra, Varanasi, India) and tap water ad libitum. All the experiments were conducted in accordance with institutional practice and within the framework of the revised Animals (Scientific Procedures) Act of 2002 of

Results

At the termination of the study, 8-hr mice had lower body weight, while 12- and 20-hr mice weighed significantly more compared to the control group (Table 1). There was also a decrease in the testicular volume of 8-hr mice but the other experimental groups were not different from controls (Fig. 1A). However, the GSI did not show any variation among the different groups of mice (Fig. 1B). The sperm count was significantly decreased in the 8-hr and increased in the 12-hr mice as compared to the

Discussion

Our results indicate that the daily injections of serotonergic and dopaminergic precursor drugs given in a particular temporal relation altered reproductive development and age-dependent body weight gain in mice. At the age of about 8 weeks (i.e. 58 days), spermatogenesis was arrested in the 8-hr group, accompanied by a low testosterone level and highly reduced sperm counts, motility and viability. In addition to these degenerative changes, abnormality was evident in 45–50% of sperms as

Acknowledgements

This work was supported by funds from the Council of Scientific and Industrial Research (CSIR), New Delhi, India, to C.M.C. (research project 37/1284/07/EMR-II). A Senior Research Fellowship to S.S. from the Indian Council of Medical Research (ICMR) is gratefully acknowledged.

References (46)

  • C.M. Chaturvedi et al.

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

    J. Neural Transm.

    (1992)
  • C.M. Chaturvedi et al.

    Effect of 12-hr temporal relation of serotonin and dopamine precursor drugs (5-HTP and l-DOPA) on photosexual responses of immature Japanese quail

    Indian J. Exp. Biol.

    (1991)
  • C.M. Chaturvedi et al.

    Photoperiodism in Japanese quail with special reference to relative refractoriness

    Indian J. Exp. Biol.

    (1993)
  • C.M. Chaturvedi et al.

    Effect of timed administration of neurotransmitter drugs on testicular activity, body weight and plumage pigmentation in the lal munia, Estrilda amandava

    Indian J. Exp. Biol.

    (1994)
  • C.M. Chaturvedi et al.

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

    J. Exp. Zool.

    (2006)
  • G. Danscher

    Light and electron microscopic localization of silver in biological tissue

    Histochemistry

    (1981)
  • A.C. Emata et al.

    Temporal variations in gonadal body fat responses to daily injections of 5-hydroxytryptophan (5-HTP) and dihydroxyphenylalanine (DOPA) in the gulf killifish, Fundulus grandis

    J. Exp. Zool.

    (1985)
  • A.P. Hoffer

    Effects of gossypol on the seminiferous epithelium in the rat: a light and electron microscope study

    Biol. Reprod.

    (1983)
  • R. Jaiwal et al.

    Elimination of testicular regulation by 12 h temporal relationship of serotonergic and dopaminergic activity in Indian palm squirrel, Funambulus pennanti

    J. Neural Transm.

    (1991)
  • A.E. Jimenez et al.

    L-3,4-dihydroxyphenylanine (l-DOPA) as an inhibitor of prolactin release

    Endocrinology

    (1978)
  • P. Kumar et al.

    Effects of stimulated hypo- and hyper-reproductive conditions on the characteristics of circadian rhythm in hypothalamic concentration of serotonin and dopamine and in plasma levels of thyroxine, triiodothyroxine, and testosterone in Japanese quail, Coturnix coturnix japonica

    Chronobiol. Int.

    (2009)
  • A.H. Meier et al.

    Temporal synergism of corticosterone and prolactin controlling gonadal growth in sparrow

    Science

    (1971)
  • L.J. Miller et al.

    Temporal synergism of neurotransmitter-affecting drugs influences seasonal conditions in sparrows

    J. Interdiscip. Cycle Res.

    (1983)
  • Cited by (14)

    • Expression of arginine vasotocin and estrogen receptor alpha (ERα) in the shell gland altered by the specific phase relations of neural oscillations affects the reproductive physiology of Japanese quail

      2016, Physiology and Behavior
      Citation Excerpt :

      Further, 12-h temporal phase relations of neural oscillations alter the photo sexual responses of immature Japanese quail [19] while the 8-h relation of serotonergic and dopaminergic drugs induce reproductive regression in quail under relatively short-day lengths and exhibit scotosensitive responses under short days [20]. Specific phase relations of neural oscillations are also reported to modulate reproduction in mammals whether seasonal (Syrian hamster - [21]; Indian Palm Squirrel - [22] or continuous breeders (laboratory mice) -[23]. Thus, both photoperiod and specific temporal phase relations of neural oscillations appear to be regulators of gonadal development/activity in many avian and mammalian species.

    • Nesfatin-1: Localization and expression in avian gonads and its modulation by temporal phase relation of neural oscillations in female Japanese quail, Coturnix coturnix japonica

      2015, General and Comparative Endocrinology
      Citation Excerpt :

      Although, nesfatin-1 has been identified in the chicken genome, no report is available on the possible tissue expression or function of this molecule in avian species. Regarding regulation of avian reproduction, several studies have reported that injections of 5-HTP (5-hydroxytryptophan, the serotonin precursor) and l-DOPA (l-dihydroxyphenylalanine, the dopamine precursor) are thought to reset the phase of two circadian neuroendocrine mechanism with serotonergic and dopaminergic components and thereby determine seasonality/reproductive activities of many vertebrate species (Meier et al., 1981; Chaturvedi and Bhatt, 1990; Chaturvedi and Jaiwal, 1990; Chaturvedi and Prasad, 1991; Kumar and Chaturvedi, 2009; Sethi and Chaturvedi, 2009). In these species, including Japanese quail, 8-h and 12-h temporal phase relation of serotonergic and dopaminergic neural oscillations are gonado-suppressive and gonado-stimulatory respectively, but other relations i.e., 5-HTP and l-DOPA if given at the interval of 0 h, 4 h, 16 h and 20-h are found to be ineffective (Chaturvedi and Bhatt, 1990; Phillips and Chaturvedi, 1995; Kumar and Chaturvedi, 2009).

    • Interaction of specific temporal phase relations of circadian neural oscillations and long term photoperiodic responses in Japanese quail, Coturnix coturnix japonica

      2015, General and Comparative Endocrinology
      Citation Excerpt :

      Further, 12-h temporal phase relations of neural oscillations alter the photo sexual responses of immature Japanese quail (Chaturvedi et al., 1991) while the 8-h relation of serotonergic and dopaminergic drugs induce reproductive regression in quail under relatively short-day lengths (<11 h) and exhibit scotosensitive responses under short days (Bhatt and Chaturvedi, 1992a). Specific phase relations of neural oscillations are also reported to modulate reproduction in mammals whether seasonal (Syrian hamster- Wilson and Meier, 1989; Indian Palm Squirrel- (Chaturvedi and Jaiwal, 1990; Jaiwal and Chaturvedi, 1991; Chaturvedi and Singh, 1992; Singh and Chaturvedi, 1993) or continuous breeders (laboratory mice- Sethi and Chaturvedi, 2009; Sethi et al., 2010). Thus, both photoperiod and specific temporal phase relations of neural oscillations appear to be regulators of gonadal development/activity in many avian and mammalian species.

    • Age-dependent variation in the RFRP-3 neurons is inversely correlated with gonadal activity of mice

      2010, General and Comparative Endocrinology
      Citation Excerpt :

      Histological sections of the testis were viewed under a microscope (Axioskop 2 Plus; Carl Zeiss AG, Oberkochen, Germany) and images were captured with a digital camera. Seminiferous tubule diameter was determined in 10 sections per mouse testis by using the image analyzer software Motic Images 2000 version 1.3 (Sethi and Chaturvedi, 2009). A radioimmunoassay (RIA) of plasma testosterone was performed using a commercial RIA kit (Immunotech, Marseille, France) according to the manufacturer’s instructions.

    View all citing articles on Scopus
    View full text