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: Results indicate that 12-h phase relation of neurotransmitter precursors not only initiates early onset of scotorefractoriness i.e., full development of gonad even under short-day length but maintains it continuously (a long lasting effect) unlike control and the 8-h relation dissipates it, making the quail scotosensitive.
4 citations
TL;DR: The experiments suggest that the temporal phase relations of circadian neural oscillations, in addition to modulating the classical photoperiodic responses, may also modulate the gonadal responses to blue (suppressive) and red (stimulatory) light in Japanese quail.
Abstract: Avian literature reports the modulation of 'photoperiodic gonadal responses' by the temporal phase relation of serotonergic and dopaminergic oscillations in Japanese quail. But, the modulation of 'light colour responses' by the temporal synergism of neural oscillations is not yet known. Hence the present study was designed to investigate the interaction of the light colour (blue, red) and the phase relation of neural oscillations in the reproductive regulation of Japanese quail. Three week old male Japanese quail were divided into two groups and maintained under a long day length condition (16L:8D) and were exposed to a 30 lux intensity of blue LED (light emitting diode) (B LED) and a red LED light (R LED). At the age of 15.5weeks, quail of one subgroup of B LED were injected with serotonin precursor (5-HTP) and dopamine precursor (l-DOPA) 12hrs apart (B LED+12-hr) and those of the R LED group were injected with the same drugs (5mg/100g body weight over a period of thirteen days) but 8hrs apart (R LED+8-hr). The remaining subgroups of both the light colour groups (B LED & R LED) received normal saline twice daily and served as controls. Cloacal gland volume was recorded weekly until 35.5weeks of age when the study was terminated and reproductive parameters (testicular volume, GSI, seminiferous tubule diameter and plasma testosterone) were assessed. Results indicate that the 8-hr temporal phase relation of neural oscillations suppresses reproductive activity even during the photosensitive phase of the red light exposed quail (R LED+8-hr) compare to the R LED controls. On the other hand, the 12-hr temporal phase relation stimulates the gonadal development of the B LED+12-hr quail compared to the B LED controls which after completing one cycle entered into a regressive phase and remained sexually quiescent. These experiments suggest that the temporal phase relations of circadian neural oscillations, in addition to modulating the classical photoperiodic responses, may also modulate the gonadal responses to blue (suppressive) and red (stimulatory) light. These studies led us to conclude that the temporal phase relation of serotonergic and dopaminergic oscillations is not only an important regulator of avian reproduction but may also override the classical effects of light colours in Japanese quail.
2 citations
TL;DR: Findings indicate that it is not the dose of neurotransmitter precursor drugs (5-HTP and L-DOPA) and the neurotransmitters (serotonin and dopamine itself) that cause the effect, instead it is the function of interval between the drug administration which induces or entrains specific phase relation between serotonergic and dopaminergic oscillations.
Abstract: Specific temporal phase relation of serotonergic and dopaminergic oscillations alters reproductive responses in many species. Aim of the study was to confirm whether effect of serotonergic drug (5-HTP) and dopaminergic drug (L-DOPA) is due to their conversion into serotonin and dopamine respectively or other products. For this study, PCPA (p-chlorophenylalanine, a long lasting inhibitor of serotonin synthesis), DDC (Diethyldithiocarbamate, which inhibits biosynthesis of nor-adrenaline), α-MT (Methyl-p-tyrosine, an inhibitor for the conversion of tyrosine to DOPA) and DOPS (Dihydroxyphenylserine, a specific precursor for noradrenaline) were used in different groups in addition to 5-HTP and L-DOPA given at specific time interval. Reproductive responses monitored at 10 weeks post treatment indicate that gonadal activity was significantly low in HTP:DOPA (8-hr quail), HTP+PCPA:DOPA and HTP:DOPA+DDC quail compare to control (S:S). However, gonadal activity of HTP:S(HTP control), S:DOPA(DOPA control) and HTP:α-MT+DOPS was not different from S:S control and remained in active condition. These findings indicate that it is not the dose of neurotransmitter precursor drugs (5-HTP and L-DOPA) and the neurotransmitters (serotonin and dopamine itself) that cause the effect, instead it is the function of interval between the drug administration which induces or entrains specific phase relation between serotonergic and dopaminergic oscillations. Further, gonadal suppression observed in HTP:DOPA, HTP+PCPA:DOPA and HTP:DOPA+DDC group three groups is not due to injection of 5-HTP or L-DOPA (alone) but due to conversion of administered 5-HTP into serotonin and conversion of L-DOPA (administered) into dopamine; not due to their further conversion into catecholamines other than dopamine i.e. noradrenaline or adrenaline.
1 citations
Cites background or methods from "Elimination of testicular regressio..."
...The length and width of the cloacal gland was measured in situ with dial calipers weekly; before, during and after the treatment upto the termination of study and cloacal gland volume was calculated in cm3 (Jaiwal and Chaturvedi, 1991; Chaturvedi et al., 1993)....
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...…2003) and mammalian species whether seasonally breeding (Syrian hamster- Wilson and Meier, 1989; Indian palm squirrel- Chaturvedi and Jaiwal, 1990; Jaiwal and Chaturvedi, 1991; Chaturvedi and Singh, 1992) or continuous breeder (laboratory mouse, Mus musculus- Sethi and Chaturvedi, 2009; Sethi et…...
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TL;DR: 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.
Abstract: 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.
1 citations
References
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01 Jan 1968
TL;DR: In this paper, the authors present an analysis of correlation and correlation coefficients for the Mann-Whitney Test, the Newman-Keuls' and Tukey Mulitple-Comparison Tests, and the Signed-Pairs, Signed-Ranks Test.
Abstract: 1. Organizing Data and Some Simple Computations. 2. Confidence Intervals. 3. Correlation and Related Topics. 4. Analysis of Variance. 5. Supplemental Computations for Analysis of Variance. 6. Multivariate Analyses. 7. Nonparametric Tests, Miscellaneous Tests of Significance, and Indexes of Relationships. Appendices. Normal-Curve Areas. Critical Values of "Student's" t Statistic. Critical Values for Sandler's A Statistic. Values of the Chi-Square Statistic. Probabilities of the F Distribution. Fisher's z Transformation for Pearson's r Correlation Coefficient. Critical Values of Pearson's r Correlation Coefficient for Five Alpha Significance Levels. Critical Values of the U Statistic of the Mann-Whitney Test. Critical Values for Hartley's Maximum F Ratio Significance Test for Homogeneity of Variances. Significant Studentized Ranges for Duncan's New Multiple-Range Test. Significant Studentized Ranges for the Newman-Keuls' and Tukey Mulitple-Comparison Tests. Dunnett's Test: Comparison of Treatment Means with a Control. Critical Values of Wilcoxon's t Statistic for the Matched- Pairs, Signed-Ranks Test. Coefficients for Orthogonal Polynomials. Cumulative Probability Distribution for r', the Total Number of Runs Up or Down. Sample Size and Power.
2,042 citations
"Elimination of testicular regressio..." refers methods in this paper
...To analyze time course effects within groups test of goodness of fit of linear regression was applied and Student's t-test was used to compare the significance of difference between control and treated group ( Bruning and Kintz, 1977 )....
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01 Oct 1976
TL;DR: The available evidence strongly suggests the participation of the pineal gland and the suprachiasmatic nucleus (SCN) in the photoperiodic regulation of mammalian reproductive cycles, however, little is known regarding concrete physiological mechanisms.
Abstract: Many mammalian species display seasonal breeding patterns correlated with annual cycles of change in the physiology and morphology of the reproductive system. Such annual reproductive cycles are often photoperiodically controlled (i.e, the annual change in day length determines when reproductive activity begins and when it ends within the annual cycle). Photoperiodic control of seasonally appropriate changes in reproductive activity is dependent on an endogenous time measuring process. Among mammals the physiological basis of photoperiodic time measurement has been studied most extensively in the golden hamster. Studies with this species indicate that photoperiodic time measurement is executed by the circadian system. The time measuring process depends on a circadian oscillation of responsiveness to light with properties similar to those of the hypothetical rhythm originally proposed by Bunning to explain photoperiodic phenomena in plants. The available evidence strongly suggests the participation of the pineal gland and the suprachiasmatic nucleus (SCN) in the photoperiodic regulation of mammalian reproductive cycles. However, little is known regarding concrete physiological mechanisms, and the extent to which the SCN and the pineal gland may participate in the time measuring process per se remains to be determined.
297 citations
266 citations
TL;DR: Results indicate that the neuroendocrine— gonadal axis may normally be refractory to pineal secretory products during the summer months or the pineal gland may be physiologically “exhausted” after a period of activity.
Abstract: When intact adult male golden hamsters are exposed to natural photoperiodic and temperature conditions during the winter months, their reproductive organs degenerate and plasma levels of LH decrease significantly. Pinealectomized hamsters kept under identical conditions do not experience the winter decline in reproductive activity. As spring approaches, the gonads of the non—pinealectomized hamsters regenerate to a functionally mature state. If hamsters with intact pineal glands are placed in near continuous darkness beginning in May (after having experienced reproductive atrophy in the previous winter), their reproductive systems do not regress. These results indicate that the neuroendocrine— gonadal axis may normally be refractory to pineal secretory products during the summer months or the pineal gland may be physiologically “exhausted” after a period of activity. The findings show that: (a) the photoperiod normally controls the seasonal reproductive rhythm in this species, and (b) the effects are medi...
165 citations
TL;DR: The ability of the 5‐ HT neurons to take up and accumulate 5‐HT in the presence of5‐HTP is relatively low in spite of large amounts of 5-HTP present in the brain neuropil after extracerebral decarboxylase inhibition.
Abstract: The histochemical effects of 500 and 1000 mg/kg of dl-5-hydroxy-tryptophan (5-HTP), both alone and in combination with a peripheral decarboxylase inhibitor (seryl-trihydroxy benzyl hydrazine; Ro 4–4602) have been examined on central monoamine neurons of rats by the Falck-Hillarp fluorescence technique that demonstrates monoamines and their precursors. 5-HTP alone or together with Ro 4–4602 caused only weak intraneuronal accumulation of 5-HT in the central 5-HT neurons, in spite of an increased entry of 5-HTP into the brain after Ro 4–4602 treatment, as shown by an increase in the specific neuropil fluorescence and a reduction of 5-HT accumulation in the cells of the capillary walls. Ro 4–4602 markedly potentiated the effects of 5-HTP on the central dopamine neurons, many of which became clearly yellow fluorescent. The mechanism of dopamine depletion by 5-HTP is probably therefore mainly one of displacement. The effects on the noradrenaline neurons were also potentiated by Ro 4–4602 pretreatment, the neurons exhibiting a yellow-green fluorescence. This depletion may therefore also be mainly be due to amine displacement. It is concluded that the ability of the 5-HT neurons to take up and accumulate 5-HT in the presence of 5-HTP is relatively low in spite of large amounts of 5-HTP present in the brain neuropil after extracerebral decarboxylase inhibition.
156 citations