226 Specialia EXPERIENTIA 33/2 Examination of the differences between control and CVF- treated animals at each 3-h-period demonstrates that the total leukocytic and neutrophilic response to CVF is de- pendent upon the time of day the factor is given. Total leukocytic and neutrophilic response is greater during the early morning (06.00-09.00 h} than during the afternoon (12.00-18.00 h). The lymphocytes on the other hand, showed little difference in variation and increase fol- lowing CVF administration. McCall et al. 4 reported alterations in neutrophil kinetics in the rabbit after CVF activation of the complement cascade. Following intravenous injection of 0.6 to 1.0 ml of purified cobra venom factor, a profound neutropenia occurred within 60-120 sec followed by a marked neutro- philia. In this same study, CVF was injected into Cs-de- ficient rabbits which again caused an initial neutropenia followed by a neutrophilia. To further characterize the active factor, fresh plasma was treated with CVF and filtered through a 20,000 MW filter. The filtrate was then injected into the rabbit ear vein and the same neutro- philic response obtained. These results suggested that the neutrophilic changes depended on the elaboration of a factor of low molecular weight (<20,000) which may be derived from either C a or C54. Because the present investigation was concerned with only a 45-rain-response, a neutropenia was not observed. However, a 10fold increase between the 24-h-mean con- trol and experimental neutrophil levels was evident, con- firming the neutrophilia following CVF activation of the complement cascade 4. It is not known whether complement regulates hourly variations in neutrophil kinetics. However, this study has demonstrated that the extent of the neutrophilia fol- lowing CVF complement activation in the rat is a time- dependent phenomena which varies according to the time of day the factor is given and has a circadian rhythm. Electrically excitable neurosecretory cell bodies in the periphery of the stick insect, Carausius morosus I. Orchard 1 and L. H. Finlayson Department of Zoology and Comparative Physiology, University o] Birmingham, P. O. Box 363, Birmingham B75 2TT (England), 15 July 1976 Summary. Intracellular recordings have been made from the cell bodies of both neurosecretory and non-neurosecretory multipolar neurons in the periphery of Carausius morosus. The neurosecretory neurons have cell bodies which are electrically excitable and produce overshooting action potentials, whilst the cell bodies of the non-neurosecretory neurons are electrically inexcitable. There is a sparsity of electrophysiological data about the basic membrane properties underlying neuroendocrine integration and regulation in insects, A suitable prepara- tion for such a study is found in the stick insect, in which multipolar neurons showing the ultrastructural charac- teristics of being neurosecretory have been described 3, 3. These multipolar neurosecretory neurons, the link nerve neurons (LNNs), lie with their cell bodies on or near the link nerve and have processes passing superficially along a number of major peripheral nerves~, 3. Each of the processes propagates action potentials towards their terminals where presumably release of neurosecretory material is triggered a. As a preliminary to investigating the control mechanisms of these cells, intracellular recordings were made to determine the properties of the membrane of the cell body. Previous intracellular recordings from nerve cell bodies of insects have been confined to monopolar neurons in the central nervous system. The majority of these cell bodies are electrically inexcitable 4, although a specific group of dorsally situated cell bodies are electrically excitable ~, 8. In this study we provide the first account of intracellular recordings from multipolar neurons in insects and present evidence for the presence of overshooting action poten- tials recorded from the cell bodies of LNNs. Adult stick insects were dissected mid-dorsally, pinned out on 'Sylgard' (Dow Corning Corporation) and the gut removed. The preparation was flooded with a modified version of Wood's saline 7 (composition: KC1, 18 raM; MgC12, 50 raM; CaCI~, 7.5 mM; NaH2PO 4 6 mM; NaHCO 3, 9 mM; glucose 185 mM; made up to 1000 ml H~O). A window was cut through the cuticle and tissue under- lying the LNNs of an abdominal segment, and the pre- paration viewed under a compound microscope by inter- terence contrast using transmitted light. In this way the insertion of microelectrodes was under visual control, providing no doubt as to the intracellular nature of the recordings and their origin in the soma. Glass micro electrodes of between 40 and 60 MsQ resistance filled with 3 M KC1 were used for intracellular recording, and current injection was provided through the same electrode using a bridge circuit (Mentor N-950 Intracellular probe sys- tem). Insertion of a microelectrode into a neurosecretory cell body revealed negative resting potentials of 30-62 mV (mean 46 mV, n = 50). The total membrane resistance of the cells was found by applying hyperpolarizing current pulses and varied from 40 to 80 MD (mean 58 MD, n = 10). Total time constant was found to be 30-50 ms (mean 43 ms, n = 10). Assuming the cell to be a sphere of 40 ~m diameter and the time constant to be the time taken for the membrane to reach 63% of its final value s (10 ms), the specific membrane resistance can be calcu- 1 We are grateful to the Science Research Council for financial sup- port and to Drs Benjamin, Swindale and Slade for allowing us a preview of their manuscript in press. 2 L. H. Finlayson and M. P. Osborne, J. Insect Physiol. 14, 1793 (1968). 3 I. Orchard and L. H. Finlayson, J. comp. Physiol. 107, 327 (1976). 4 R. M. Pitman, C. D. Tweedle and M. J. Cohen, Science, N. Y. 507 (1972). 5 G. Hoyle, D. Dagan, B. Moberley and W. Colquhoun, J. exp. Zool. 787, 159 (1974). 6 A. R. Crossman, G. A. Kerkut, R. M. Pitman and R. J. Walker, Comp. Biochem. Physiol. 40A, 579 (1971). 7 D. W. Wood, J. Physiol. Lond. 738, 119 (1957). 8 E. Stefani and A. B. Steinbaeh, J. Physiol, Lond. 203, 383 (1969).