Vilim F S, Cropper E C, Price D A, Kupfermann I, Weiss K R
Center for Neurobiology and Behavior, College of Physicians and Surgeons, Columbia University, New York, New York 10032, USA.
J Neurosci. 1996 Dec 15;16(24):8105-14. doi: 10.1523/JNEUROSCI.16-24-08105.1996.
To gain insights into the physiological role of cotransmission, we measured peptide release from cell B15, a motorneuron that utilizes ACh as its primary transmitter but also contains putative peptide cotransmitters, the small cardioactive peptides (SCPs) and the buccalins (BUCs). All stimulation parameters used were in the range in which B15 fires in freely moving animals. We stimulated neuron B15 in bursts and systematically varied the interburst interval, the intraburst frequency, and burst duration. Both peptides were preferentially released when B15 was stimulated at higher intra- or interburst frequencies or with longer burst durations. Across stimulation patterns, the amount of peptide released depended on the mean frequency of stimulation and was independent of the specific pattern of stimulation. The parameters of stimulation that produce a larger release of peptides correspond to those that evoke larger contractions. Large and frequent contractions are likely to fuse or summate, thus disrupting the rhythmic behavior mediated by the muscle innervated by motorneuron B15. Because the combined effect of the SCPs and BUCs is to accelerate the relaxation and shorten the duration of muscle contractions, these peptides reduce the probability of the disruptive fusion or summation of muscle contractions. Because these cotransmitters regulate an aspect of muscle contractions that is not controlled by acetylcholine (ACh), the primary transmitter of B15, we suggest that peptides and ACh form parallel but functionally distinct lines of transmission at the neuromuscular junction. Both types of transmission may be necessary to ensure that behavior remains efficient over a wide range of conditions.
为深入了解共传递的生理作用，我们测量了细胞B15（一种运动神经元）的肽释放情况。该运动神经元以乙酰胆碱作为主要递质，但也含有假定的肽类共递质，即小的心脏活性肽（SCPs）和颊肽（BUCs）。所有使用的刺激参数都在自由活动动物中B15放电的范围内。我们以脉冲形式刺激神经元B15，并系统地改变脉冲间隔、脉冲内频率和脉冲持续时间。当以较高的脉冲内或脉冲间频率或较长的脉冲持续时间刺激B15时，两种肽都优先释放。在各种刺激模式下，释放的肽量取决于刺激的平均频率，且与特定的刺激模式无关。产生更大肽释放量的刺激参数与引起更大收缩的参数相对应。大且频繁的收缩可能会融合或叠加，从而破坏由运动神经元B15支配的肌肉所介导的节律性活动。由于SCPs和BUCs的联合作用是加速肌肉松弛并缩短肌肉收缩的持续时间，这些肽降低了肌肉收缩发生破坏性融合或叠加的可能性。由于这些共递质调节肌肉收缩的一个方面，而该方面不受B15的主要递质乙酰胆碱（ACh）的控制，我们认为肽和ACh在神经肌肉接头处形成了平行但功能不同的传递途径。两种类型的传递可能都是确保行为在广泛条件下保持高效所必需的。
