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Arecoline is known to cause endocrine dysfunction. In the current article role of arecoline on pineal–testis activity was investigated in hypothyroid rats induced by propylthiouracil (PTU). PTU treatment caused thyroid dysfunction ultrastructurally with a fall in T3 and T4 levels followed by a rise of thyroid stimulating hormone (TSH) level. Pineal activity was impaired by PTU treatment, as evident from degenerated synaptic ribbons and mitochondria of the pinealocytes with depletion of pineal and serum N-acetyl serotonin and melatonin levels. Leydig cell function was suppressed, evident from reduced smooth endoplasmic reticulum and depletion of testosterone level. Sex accessories function was impaired by showing scanty rough endoplasmic reticulum with depletion of fructose and sialic acid levels. Arecoline treatment that caused pineal dysfunction and testicular stimulation in control rats, suppressed both pineal and testis functions after PTU treatment. The findings suggest that arecoline inhibits pineal–testis function in experimentally induced hypothyroid rats. [ABSTRACT FROM AUTHOR]

Millions of people consume betel nut for increased capacity to work and for stress reduction. The nut contains arecoline, which has multiple side effects on endocrine functions. Objective of the work is to investigate pineal–testicular responses to noise and after arecoline treatment in noise in rats. Noise exposure (100 dB, 6 h daily, 10 days) caused pineal stimulation ultrastructurally and at indoleamines level. Leydig cell dysfunction with fall of testosterone level and suppression of sex accessories were noticed. In contrast, pineal activity was inhibited and reproductive functions were stimulated after arecoline administration, confirmed from reversed changes to those of noise. Arecoline treatment in noise exposure showed same results as in noise both in pineal and in reproductive functions. It is concluded that noise causes testicular dysfunction probably by gonadotropin suppression induced by pineal melatonin in noise. Furthermore, arecoline cannot prevent it in noise in rats. [ABSTRACT FROM AUTHOR]

The aim of the current investigation was to study the effect of lithium on circadian rhythms of pineal – testicular hormones by quantitations of pineal and serum serotonin, N-acetylserotonin and melatonin, and serum testosterone at four time points (06.00, 12.00, 18.00 and 24.00) of a 24-hr period under normal photoperiod (L:D), reversed photoperiod (D:L), constant light (L:L) and constant dark phase (D:D) in rats. Circadian rhythms were observed in pineal hormones in all the combinations of photoperiodic regimens, except in constant light, and in testosterone levels in all the photoperiodic combinations. Pineal and serum N-acetylserotonin and melatonin levels were higher than serotonin at night (24.00 hr), in natural L:D cycle, in reversed L:D cycle or similar to normal L:D cycle in constant dark phase, without any change in constant light. In contrast, testosterone level was higher in light phase (12.00 hr through 18.00 hr) than in the dark phase (24.00 hr through 06.00 hr) in normal L:D cycle, in reversed L:D cycle, similar to normal L:D cycle in constant dark (D:D), and reversed to that of the normal L:D cycle in constant light (L:L). Lithium treatment (2 mEq/kg body weight daily for 15 days) suppressed the magnitude of circadian rhythms of pineal and serum serotonin, N-acetylserotonin and melatonin, and testosterone levels by decreasing their levels at four time points of a 24-hr period in natural L:D or reversed D:L cycle and in constant dark (D:D). Pineal indoleamine levels were reduced after lithium treatment even in constant light (L:L). Moreover, lithium abolished the melatonin rhythms in rats exposed to normal (L:D) and reversed L:D (D:L) cycles, and sustained the rhythms in constant dark. But testosterone rhythm was abolished after lithium treatment in normal (L:D)/reversed L:D (D:L) cycle or even in constant light/dark. The findings indicate that the circadian rhythm exists in pineal hormones in alternate light – dark cycle (L:D/D:L) and in constant dark (D:D), but was absent in constant light phase (L:L) in rats. Lithium not only suppresses the circadian rhythms of pineal hormones, but abolishes the pineal melatonin rhythm only in alternate light – dark cycles, but sustains it in constant dark. The testosterone rhythm is abolished after lithium treatment in alternate light – dark cycle and constant light/dark. It is suggested that (a) normal circadian rhythms of pineal hormones are regulated by pulse dark phase in normal rats, (b) lithium abolishes pineal hormonal rhythm only in pulse light but sustains it in constant dark phase, and (c) circadian testosterone rhythm occurs in both pulse light or pulse dark phase in normal rats, and lithium abolishes the rhythm in all the combinations of the photoperiod. The differential responses of circadian rhythms of pineal and testicular hormones to pulse light or pulse dark in normal and lithium recipients are discussed. [ABSTRACT FROM AUTHOR]