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.
Citations
More filters
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 [...
[...]
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)....
[...]
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....
[...]
...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....
[...]
References
More filters
TL;DR: It is manifested that 12 hour relationship of these two neural oscillations may induce breeding conditions (summer), 8 hour relationship induced post reproductive regressive/photorefractory condition (late summer) and 4‐hour relationship induced...
Abstract: To study the reproductive and metabolic effects of circadian serotonergic and Dopaminergic activities, 5‐hydroxytryptophan (5‐HTP, serotonin precursor) and L‐dihydroxyphenylalanine (L‐DOPA, dopamine precursor) were administered daily in different temporal relationships in Red‐headed bunting (Emberiza bruniceps) during the preparatory phase of annual gonadal cycle. L‐DOPA given daily after 12 hours of 5‐HTP injection (12‐hr relationship) induced full gonadal development and fat deposition. But, L‐DOPA given after 4 hours of 5‐HTP administration (4‐hr relationship) stimulated only fat deposition without any gonadal effect. On the other hand, these two drugs injected 8‐hour apart led to significant decrease in gonadal growth as well as fat deposition. The findings manifested that 12 hour relationship of these two neural oscillations may induce breeding conditions (summer), 8 hour relationship induced post reproductive regressive/photorefractory condition (late summer) and 4‐hour relationship induced...
32 citations
"Suppression of annual testicular de..." refers background in this paper
...Specific phase relation of these precursor drugs is also reported to influence reproductive seasonality in white throated sparrow (Miller and Meier, 1983) Japanese quail (Chaturvedi and Meier, 1988) Red headed bunting (Chaturvedi and Bhatt, 1990); Spotted munia (Chaturvedi and Prasasd, 1991); Gulf Killifish (Emata etal....
[...]
TL;DR: D-DOPA was considered to be metabolized to dopamine only in the kidney, most of which is excreted directly into the urine, from these results.
Abstract: The radioactive metabolites of D-and L-isomers of 3, 4-dihydroxyphenylalanine-(DOPA)-2-14C in the urine and the main tissues were comparatively investigated after intravenous and oral administration to rats. After administration of L-DOPA, eighteen metabolites were detected in the urine and dopamine conjugate, dopamine, homovanillic acid (HVA), 3, 4- dihydroxyphenylacetic acid (DOPAC) and 3-methoxy-4-hydroxyphenyl ethanol (MHPE) conjugate were found to be the main metabolites, while excretion as DOPA was only less than 1%. After administration of D-DOPA, an appreciable amount (20%) was excreted as unchanged DOPA, but dopamine, mostly in the free form, was found to be the main metabolite. After administration of L-DOPA, dopamine and its metabolites were the main component in the tissues including the brain and skeletal muscle, while after that of D-DOPA, 3-O-methyl-DOPA was the only metabolite, except the kidney where dopamine and its metabolites were found to be formed. It was demonstrated that approximately 67 and 53% of the brain radioactivity was dopamine and its metabolites at 10 and 60 min after intravenous and oral administration of L-DOPA-14C, respectively. The main metabolite in the pancreas and intestine from L-DOPA was DOPAC and dopamine conjugate, respectively, while unchanged DOPA from D-DOPA. In the liver, where D-DOPA dose not accumulate, dopamine conjugate was the main metabolite from L-DOPA, while no dopamine from D-DOPA. From these results, D-DOPA was considered to be metabolized to dopamine only in the kidney, most of which is excreted directly into the urine.
27 citations
TL;DR: The results indicate that interaction between these two systems does not produce any pharmacological effect but actually affects the seasonality of the birds, as indicated by the different gonadal and metabolic conditions that followed differently timed daily injections of drugs that influence serotonergic and dopaminergic activities.
Abstract: The present study was designed to examine the role of circadian organization in the control of seasonality in the seasonally breeding spotted munia, Lonchura punctulata, which does not utilize photoperiod to time its reproduction under natural day-length conditions.
Daily injections of L-dihydroxyphenylalanine (L-DOPA, precursor of dopamine) given 12 hr and 8 hr after administration of 5-hydroxytryptophan (5-HTP, precursor of serotonin) alter the gonadal and body-weight responses of the spotted munia, when it is maintained under short-day conditions (LD 6:18). The 12-hr interval was stimulatory and the 8-hr interval was inhibitory for both gonadal and body-weight responses while other intervals (0, 4, and 16 hr) had no effect. A 20-hr interval was stimulatory only for gonadal growth and had no effect on body weight.
These findings support the suggestion that the endogenous seasonal mechanism is determined by circadian organization (i.e., by changes in the phase relationships of two neural oscillations and their many other circadian expressions). The results also indicate that interaction between these two systems does not produce any pharmacological effect but actually affects the seasonality of the birds, as indicated by the different gonadal and metabolic conditions that followed differently timed daily injections of drugs that influence serotonergic and dopaminergic activities. Furthermore, the mechanism of regulation of seasonality seems to be similar in species that do and do not utilize day length as the primary regulator with which to time their seasonal reproductive and metabolic cycles.
24 citations
TL;DR: The site of the inhibitory effect of L-3,4- dihydroxyphenylalanine (L-dopa) on prolactin release was determined in the hypothalamus and anterior pituitary of estrogen/progesterone-treated, ovariectomized rats andHypothalamic concentrations of endogenous DA were significantly increased 30 min after L- dopa and were correlated with decreased serum prolactIn levels at this time.
Abstract: A series of experiments was performed on estrogen/progesterone-treated, ovariectomized rats to determine the site of the inhibitory effect of L-3,4- dihydroxyphenylalanine (L-dopa) on prolactin release. After intraarterial injection of L-[3H]dopa (150 μCi), [3H]norepinephrine ([3H]NE), [3H]dopamine ([3H]DA), and L-[3H]dopa were found in the hypothalamus and anterior pituitary. Intra-arterial injection of L-dopa (2, 5, or 10 mg/kg) produced a dose-related inhibition of prolactin release. The magnitude and the duration of inhibition of prolactin release were greater with increasing doses of L-dopa. Hypothalamic concentrations of endogenous DA were significantly increased 30 min after L-dopa (10 mg/kg) and were correlated with decreased serum prolactin levels at this time. Hypothalamic NE content was not affected. L-α-Methyldopa hydrazine, 20 mg/kg (Mk 486), a peripheral aromatic L-amino acid decarboxylase inhibitor, injected 30 min before L-[3H]dopa injection, increased the concentration of L-[3H]dopa in th...
22 citations
"Suppression of annual testicular de..." refers background in this paper
...These doses of neurotransmitter precursors are reported to increase brain content of Serotonin (Fuxe et al., 1971; Bobillier etal., 1975; Korf et al., 1974) and Dopamine (Shindo etal., 1973; Jimenez et al., 1978) respectively in rats....
[...]
TL;DR: It is suggested that response in the present study is not a pharmacological effect of drugs but temporal synergism of neural acitivities affected the seasonality of reproduction as only 12-hour-relation of 5-HTP and L-DOPA maintained breeding activity during post reproductive phase of annual gonad cycle in Palm Squirrel.
Abstract: Daily injections of L-dihydroxyphenylalanine (L-DOPA, dopamine precursor) given 12 hour after 5-hydroxytryptophan (5-HTP, serotonin precursor) eliminated annual testicular regression in seasonally breeding sub-tropical Palm Squirrel that undergoes seasonal changes in responsiveness to day-length and humidity. Other temporal relations (L-DOPA given 0, 4, 8, 16 and 20 hours after 5-HTP administration) decreased/delayed the rate of regression and maintained the reproductive system at intermediate level. 12-hour-relation maintained full breeding condition (maximum gonad and accessory sex organs) unlike control, which exhibited complete atrophy of primary and accessory sex organs.
19 citations
"Suppression of annual testicular de..." refers background in this paper
...In Indian Palm squirrel, Funarnbulus pennanti, L-DOPA injected 12 hr after 5-HTP (12 hr relationship) eliminated seasonal gonadal regression (Chaturvedi and Jaiwal, 1990) and squirrels were maintained continuously in breeding conditions even in non-breeding season....
[...]
..., 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)....
[...]