Elimination of testicular regression by 12-hr temporal relationship of serotonergic and dopaminergic activity in Indian palm squirrel, Funambulus pennanti.

Temporal phase relation of circadian neural oscillations alters RFamide-related peptide-3 and testicular function in the mouse.

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.

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

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 (5mg/100g 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.

Reproductive phase dependent circadian variation in hypothalamic concentration of serotonin, dopamine and peripheral thyroxine levels in Japanese Quail following 5-HTP and L-DOPA administration at specific time intervals

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...

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

Abstract: The present study analyzed changes in the expression of RFamide-related peptide-3 (RFRP-3; a mammalian ortholog of avian gonadotropin-inhibitory hormone), in the brain and correlated it with testicular activity of mice of different age groups (day-old, 1-, 3-, 5-, 7-, 9-, 11-, 13-week and 15-year-old) Testicular activity after a progressive increase up to 13-week of age declined in the old mice On the other hand, while immunoreactive (ir) RFRP-3 neurons were not seen in the day-old mice, few appeared in 1-week-old mice, their number and size increased drastically at 3-week of age This condition remained unaltered until 7-week of age followed by a progressive decline up to the age of 13-week and thereafter increased again in the old age 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 It is concluded that aging mice exhibits inverse correlation of RFRP-3 neurons and gonadal activity suggesting that function of RFRP-3 is not initiated until 1-week of age and thereafter it could participate in the regulation of gonadal development

Suppression of annual testicular development in Indian Palm Squirrel, Funambulus pennanti by 8 hr temporal relationship of serotonin and dopamine precursor drugs

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.

Computational Handbook of Statistics

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.

Circadian rhythms and photoperiodic time measurement in mammals.

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.

Pineal Control of a Seasonal Reproductive Rhythm in Male Golden Hamsters Exposed to Natural Daylight and Temperature

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...

dl‐5‐Hydroxytryptophan‐induced changes in central monoamine neurons after peripheral 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.