Elimination of testicular regression by 12-hr temporal relationship of serotonergic and dopaminergic activity in Indian palm squirrel, Funambulus pennanti.
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.
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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 "Elimination of testicular regressio..."
...On the other hand, if these drugs are injected 8 h apart (8- hour relation), this may lead to gonadal suppression/non-breeding conditions, while other relations (0, 4, 16 and 20 h) have been found to be ineffective. In the Indian palm squirrel, Funambulus pennantii , the 12-hour phase relation of serotonergic and dopaminergic oscillations not only extends the breeding season, but may also eliminate annual reproductive regression [...
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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 present findings indicate that hyperactivity of the ir-RFRP-3 neurons of dorsomedial nucleus of hypothalamus (DMH) observed in prepubertal mice declines in reproductively active mice and increases again in the old mice having declined reproductive performance.
17 citations
Cites methods from "Elimination of testicular regressio..."
...The length and width of the left testis was measured in situ with dial calipers, and the testicular volume was calculated using Bissonett’s formula 4/3pab(2) (a = 1/2 of the long axis; b = 1/2 of the short axis) (Jaiwal and Chaturvedi, 1991)....
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...The length and width of the left testis was measured in situ with dial calipers, and the testicular volume was calculated using Bissonett’s formula 4/3pab2 (a = 1/2 of the long axis; b = 1/2 of the short axis) (Jaiwal and Chaturvedi, 1991)....
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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
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.
13 citations
Cites background from "Elimination of testicular regressio..."
...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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References
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TL;DR: Daily injections of neurotransmitter‐affecting drugs induced spring migratory and reproductive conditions in white‐throated sparrows, Zonotrichia albicollis, during the fall and changes in the temporal relations of circadian neural activities may account for seasonal alterations of metabolism and behavior.
Abstract: Daily injections of neurotransmitter‐affecting drugs induced spring migratory and reproductive conditions in white‐throated sparrows, Zonotrichia albicollis, during the fall. Injections of DOPA (catecholamine precursor) 12 h after 5‐HTP (serotonin precursor) was most stimulatory for development of spring conditions. Summer and fall conditions followed during subsequent months in a manner similar to the natural sequence. Changes in the temporal relations of circadian neural activities may account for seasonal alterations of metabolism and behavior.
35 citations
"Elimination of testicular regressio..." refers background in this paper
...Specific physiological conditions may be duplicated out of the season by giving timed daily injections of neurotransmitter precursor drugs (Miller and Meier, 1983; Wilson and Meier, 1989)....
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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
TL;DR: Results indicate that the pineal gland may be implicated in mediating the humdity information to control the male gonadal function in the Indian palm squirrel, Funambulus pennanti.
Abstract: The effect of two different conditions of humidity (80 +/- 5% and 40 +/- 5%) under stimulatory photoperiod (14L/10D) and high temperature (38 +/- 2 degrees C) was studied on the testes and accessory sex organs of the Indian palm squirrel, Funambulus pennanti, during the sexually active phase. High humidity (80 +/- 5%) reduced significantly the testes weight of the sham-operated animals as compared to the controls under natural environmental conditions but had no effect on that of pinealectomized animals. Moderate humidity (40 +/- 5%) did not affect the testes of sham-operated as well as pinealectomized animals, as compared to the respective controls. The seminal and prostatic weights showed no significant difference in high or moderate humidity conditions. However, the epididymal weight of the animals exposed to high humidity was significantly reduced in sham-operated animals only. Thus, these results indicate that the pineal gland may be implicated in mediating the humidity information to control the male gonadal function in the Indian palm squirrel, Funambulus pennanti.
30 citations
"Elimination of testicular regressio..." refers background in this paper
...While photoperiod has full control on the breeding cycle of hamsters (Reiter, 1975) in Indian Palm Squirrel, other environmental factor (humidity) determines the termination of seasonal breeding (Haldar and Saxena, 1988)....
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...annual reproduction in Indian Palm Squirrel, Funambulus pennanti and increased humidity is reported to initiate annual testicular regression during August/September (Haldar and Saxena, 1988)....
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...The onset of gonadal recrudescence may possibly be the beginning of scotorefractory phase when the reproductive system no longer responds to the inhibitory effects of short days (Haldar and Saxena, 1988)....
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...Full reproductive condition is maintained till July/ August followed by a seasonal regressive phase (Haldar and Saxena, 1988)....
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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 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