Ruby N F, Nelson R J, Licht P, Zucker I
Department of Psychology, University of California, Berkeley 94720.
Am J Physiol. 1993 Jan;264(1 Pt 2):R123-8. doi: 10.1152/ajpregu.1993.264.1.R123.
Female Siberian hamsters maintained in a winter photoperiod (8 h light/day) ceased to undergo daily torpor during infusion of prolactin (PRL) from osmotic minipumps; winter torpor was reinstated within 3 days of discontinuation of treatment. By contrast, PRL infusion was ineffective in suppressing daily torpor elicited by restricting food intake in female hamsters housed in a summer photoperiod (16 h light/day). Summer daily torpor was, however, completely inhibited in long-day gonadectomized male hamsters treated with testosterone (T). We suggest that the hyperprolactinemia, which in previous studies is characteristic of hamsters that sustain ablation of the suprachiasmatic nucleus, is incompatible with winter torpor. Summer torpor may be controlled by a mechanism less responsive to variations in plasma PRL concentration. Both winter and summer torpor are inhibited by exogenous T; it remains uncertain, however, whether sustained decreases in endogenous T secretion are as essential for the expression of summer as they are for winter torpor.
饲养在冬季光周期（8小时光照/天）下的雌性西伯利亚仓鼠，在通过渗透微型泵注入催乳素（PRL）期间停止了每日的蛰伏；停止治疗后3天内，冬季蛰伏恢复。相比之下，在夏季光周期（16小时光照/天）饲养的雌性仓鼠中，注入PRL对抑制因限制食物摄入引起的每日蛰伏无效。然而，用睾酮（T）治疗的长日照去势雄性仓鼠的夏季每日蛰伏被完全抑制。我们认为，在先前研究中，高催乳素血症是维持视交叉上核消融的仓鼠的特征，与冬季蛰伏不相容。夏季蛰伏可能由一种对血浆PRL浓度变化反应较小的机制控制。冬季和夏季蛰伏都受到外源性T的抑制；然而，内源性T分泌的持续减少对于夏季蛰伏的表达是否像对冬季蛰伏一样至关重要仍不确定。
