In the mammalian pineal gland, the rhythm in melatonin biosynthesis depends on the norepinephrine (NE)-driven regulation of arylalkylamine N-acetyltransferase (AANAT), the penultimate enzyme of melatonin biosynthesis. A recent study showed that phytocannabinoids like tetrahydrocannabinol reduce AANAT activity and attenuate NE-induced melatonin biosynthesis in rat pineal glands, raising the possibility that an endocannabinoid system is present in the pineal gland. To test this hypothesis, we analyzed cannabinoid (CB) receptors and specific enzymes for endocannabinoid biosynthesis or catabolism in rat pineal glands and cultured pinealocytes. Immunohistochemical and immunoblot analyses revealed the presence of CB1 and CB2 receptor proteins, of N-acyl phosphatidyl ethanolamine hydrolyzing phospholipase D (NAPE-PLD), an enzyme catalyzing endocannabinoid biosynthesis and of fatty acid amide hydrolase (FAAH), an endocannabinoid catabolizing enzyme, in pinealocytes, and in pineal sympathetic nerve fibers identified by double immunofluorescence with an antibody against tyrosine hydroxylase. The immunosignals for the CB2 receptor, NAPE-PLD, and FAAH found in pinealocytes did not vary under a 12 hr light:12 hr dark cycle. The CB1 receptor immunoreaction in pinealocytes was significantly reduced at the end of the light phase [zeitgeber time (ZT) 12]. The immunosignal for NAPE-PLD found in pineal sympathetic nerve fibers was reduced in the middle of the dark phase (ZT 18). Stimulation of cultured pinealocytes with NE affected neither the subcellular distribution nor the intensity of the immunosignals for the investigated CB receptors and enzymes. In summary, the pineal gland comprises indispensable compounds of the endocannabinoid system indicating that endocannabinoids may be involved in the control of pineal physiology.

中文翻译：

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大鼠松果体包含一个内源性大麻素系统。

在哺乳动物的松果体中，褪黑素生物合成的节奏取决于去甲肾上腺素（NE）驱动的芳基烷基胺N-乙酰基转移酶（AANAT）的调控，这是褪黑素生物合成的倒数第二个酶。最近的一项研究表明，像四氢大麻酚这样的植物大麻素会降低ANAT活性，并削弱NE诱导的大鼠松果体褪黑激素的生物合成，从而增加了松果体中存在大麻素系统的可能性。为了验证这一假设，我们分析了大麻素（CB）受体和特定酶在大鼠松果体和培养的松果体细胞中的内源性大麻素生物合成或分解代谢。免疫组织化学和免疫印迹分析显示，存在N-酰基磷脂酰乙醇胺水解磷脂酶D（NAPE-PLD）的CB1和CB2受体蛋白，松果体细胞和松果体交感神经纤维中的脂肪酸酰胺水解酶（FAAH）的催化内源性大麻素生物合成的酶，并通过抗酪氨酸羟化酶的双重免疫荧光鉴定。在松果体细胞中发现的CB2受体，NAPE-PLD和FAAH的免疫信号在12小时光照：12小时黑暗周期下没有变化。在亮期结束时[zeitgeber time（ZT）12]，松果体细胞中的CB1受体免疫反应显着降低。松果交感神经纤维中发现的NAPE-PLD的免疫信号在黑暗阶段的中间减少（ZT 18）。用NE刺激培养的松果体细胞既不影响亚细胞分布，也不影响所研究的CB受体和酶的免疫信号强度。综上所述，