Suppression of annual testicular development in Indian Palm Squirrel, Funambulus pennanti by 8 hr temporal relationship of serotonin and dopamine precursor drugs
TL;DR: 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.
Abstract: 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,Funambuluspennanti 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.
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TL;DR: Findings not only suggest the modulation of gonadal development in mice by changing the temporal phase relation of serotonergic and dopaminergic oscillations, but also demonstrate an inverse correlation of RFRP-3 neurons and gonadal activity in both control and experimental conditions.
Abstract: In order to study the effect of the temporal synergism of neural oscillations on reproductive regulation and the response of RFamide-related peptide-3 (RFRP-3; a mammalian ortholog of avian gonadotropin-inhibitory hormone), expression of immunoreactive RFRP-3 in the neurons of the dorsomedial nucleus of the hypothalamus was monitored in sexually immature and mature laboratory mice (study I). In study II, the effects of serotonin and dopamine precursors (5-hydroxytryptophan and L-dihydroxyphenylalanine; injected daily, 8 or 12 h apart, for 13 days in 3-week-old mice) on testicular activity and immunoreactive RFRP-3 neurons were studied until 24 days after treatment. Results indicate high levels of expression of immunoreactive RFRP-3 in the sexually immature and 8-hour mice (simulating gonadal suppression), while a low level was noted in mature and 12-hour mice (simulating gonadal stimulation). These findings not only suggest the modulation of gonadal development in mice (during the course of puberty attainment) by changing the temporal phase relation of serotonergic and dopaminergic oscillations (as in some seasonally breeding species), but also demonstrate an inverse correlation of RFRP-3 neurons and gonadal activity in both control and experimental conditions.
23 citations
Cites background from "Suppression of annual testicular de..."
...On the other hand, in this subtropical mammalian species, an 8-hour phase relation stimulates non-breeding conditions out of season [...
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TL;DR: 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, which accelerated the rate of gonadal maturation and led to more or less similar gonadal development as in the control mice.
19 citations
TL;DR: The findings suggest that the temporal phase relation of circadian serotonergic and dopaminergic oscillator varies as a function of reproductive status of the bird, and breeding/non-breeding conditions may be induced experimentally by changing the phase relationof these oscillations.
Abstract: Temporal phase relations of circadian hypothalamic neurotransmitters are reported to regulate seasonal reproduction in some avian species. Present experiments were designed to study circadian variation in the hypothalamic concentration of neurotransmitters (serotonin and dopamine) and the plasma thyroxine level in sexually active (long day) and inactive (short day) Japanese Quail. A significant circadian cycle was noted in the hypothalamic content of both serotonin and dopamine, but with different patterns. In breeding Quail, peak activity of serotonin and dopamine was noted at 10.00 A.M. and 10.00 P.M. respectively i.e. at the interval of 12 hours. However, during sexually quiescent condition, peaks of both neurotransmitters occurred at 2.00 P.M. i.e. having a 0-hour temporal relationship. During the breeding phase, the plasma thyroxine level showed a biphasic pattern with two circadian peaks at 10.00 A.M. and 10.00 P.M. whereas in the non-breeding condition a single peak was observed at 10.00 A...
16 citations
Cites background from "Suppression of annual testicular de..."
...Hamster (Wilson & Meier 1988), Indian palm squirrel (Chaturvedi & Jaiwal 1990; Jaiwal & Chaturvedi 1991; Chaturvedi & Singh 1992) and in Killfish (Emata et al. 1985)....
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TL;DR: It is suggested that administration of 5‐HTP and L‐DOPA at specific time interval and variation in pineal functions that modulate reproductive responses also alter the circadian pattern (acrophase and amplitude) of hypothalamic serotonin and dopamine, maintaining a specific phase relation between these cycles and breeding status.
Abstract: In this study, hypo‐ and hyper‐reproductive conditions, as measured by concentrations of plasma testosterone in male Japanese quail held on long days LD 16:8, were experimentally simulated with injections of 5‐hydroxytryptophan (5‐HTP) and L‐dihydroxyphenylalanine, (L‐DOPA) with 8 h and 12 h phase angle differences between them in intact and melatonin‐treated birds. The effects of these treatments were assessed on the characteristics of the circadian rhythm in the hypothalamic concentration of serotonin (5‐HT), dopamine (DA), and plasma levels of thyroxine (T4), triiodothyronine (T3), and testosterone (T). These rhythms were also studied in sham‐operated (SO), pinealectomized (Px), vehicle‐ (Veh), and melatonin (Mel)‐treated birds. On the basis of the circadian mesors of the testosterone rhythms, three distinct categories could be identified: category A (i.e., normal breeding concentrations of plasma testosterone), which includes control, sham‐operated, and vehicle‐treated groups; category A+ (i.e., conce...
11 citations
TL;DR: Results are in agreement with the internal coincidence model of photoperiodic time measurement and indicate that birds can detect specific phase relationship between the two neural oscillations for their reproductive regulations and circadian organization is intricately involved in the regulation of seasonality.
8 citations
Cites background from "Suppression of annual testicular de..."
...…discussed for birds has been reported to modulate the gonadal development of seasonally breeding mammalian species Syrian hamster (Wilson and Meier, 1989), Indian palm squirrel (Chaturvedi and Jaiwal, 1990; Chaturvedi and Singh, 1992; Jaiwal and Chaturvedi, 1991) as well as laboratory mouse....
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...The protocol discussed for birds has been reported to modulate the gonadal development of seasonally breeding mammalian species Syrian hamster (Wilson and Meier, 1989), Indian palm squirrel (Chaturvedi and Jaiwal, 1990; Chaturvedi and Singh, 1992; Jaiwal and Chaturvedi, 1991) as well as laboratory mouse....
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References
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TL;DR: It is concluded that specific phase relation (12-hr) between circadian serotonergic and dopaminergic oscillations may induce breeding condition in regressing gonad of Indian Palm Squirrel during post-reproductive phase of annual gonadal cycle.
Abstract: Specific temporal relationship (12-hr) of serotonin and dopamine activity was induced by precursor drugs (5-HTP and L-DOPA) in Indian Palm SquirrelFunambulus pennanti during testicular regression phase. This treatment established breeding condition unlike control, which experienced complete atrophy of testes and accessory sex organs.
14 citations
"Suppression of annual testicular de..." refers background in this paper
...Second study in this series reported that L-DOPA injected 12 hr after 5-HTP may even induce redevelopment of gonad up to full breeding condition when given in sexually quiescent phase of annual cycle (Jaiwal and Chaturvedi, 1991)....
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..., when two drugs were given 8 hr apart non-breeding condition was induced (present study) but when given 12hr apart breeding condition was established (Chaturvedi and Jaiwal, 1990; Jaiwal and Chaturvedi, 1991)....
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TL;DR: The role of the pineal gland in mediating the effects of photoperiod on the reproductive axis is not well established in tropical mammals, but when Indian palm squirrels (Funambulus pennanti) were exposed to sunlight, they showed marked changes in their sexual behaviour.
Abstract: The role of the pineal gland in mediating the effects of photoperiod on the reproductive axis is not well established in tropical mammals. Indian palm squirrels (Funambulus pennanti) were exposed t...
12 citations
TL;DR: The five-striped Indian palm squirrel, Funambulus pennanti, is a seasonal breeder from January to August; mature females are sexually quiescent from September to December; recrudescence of the gonad starts in late December.
Abstract: The five-striped Indian palm squirrel, Funambulus pennanti, is a seasonal breeder from January to August. Mature females are sexually quiescent from September to December; recrudescence of the gonad starts in late December. The palm squirrel is a reflex ovulator. A mature female may produce two litters of approximately three young each in one breeding season. The period of suckling is 6 weeks. Mature females experience a short period of post-lactational anoestrus during the breeding season prior to the onset of second oestrus. The role of exteroceptive factors in regulating the reproductive cycle of the palm squirrel is discussed.
11 citations
Journal Article•
TL;DR: The results indicate that the endogenous mechanism controlling seasonality may be reset by drugs that influence serotonergic and dopaminergic activity.
Abstract: To study the interaction of photoperiod and circadian neurotransmitter activity, L-DOPA L-dihydroxyphenylalanine, dopamine precursor) was administered daily, 12 hr after 5-HTP (5-hydroxy tryptophan, serotonin precursor) in sexually immature Japanese quail, raised under short photoperiod (LD8:16) since hatching. The 12 hr treatment of 5-HTP and L-DOPA was given under continuous condition of light for 11 days. After treatment the quail were transferred to intermediate day length (LD 13.5:10.5). The cloacal gland size of drug treated group increased significantly in comparison to control. The quail were then transferred to short photoperiod (LD 8:16). The cloacal gland size of both the groups started decreasing gradually but the rate was significantly low in drug treated quail in comparison to control. The results indicate that the endogenous mechanism controlling seasonality may be reset by drugs that influence serotonergic and dopaminergic activity. The 12 hr relation between the two drugs is stimulatory for gonadal growth under intermediate day length and retards the rate of regression when transferred to short days.
9 citations