摘要:

AbstractThe cockroach escape response begins with a turn away from a wind puff such as that generated by an approaching predator. The presence and direction of that wind is detected by hairs on the animal's cerci, and this information is conducted to the thoracic ganglia via two populations of giant interneurons. In the thoracic ganglia, the giant interneurons excite a number of interneurons, at least some of which in turn excite motor neurons that control leg movement. In this paper we examine response properties of various thoracic neurons to wind stimuli originating from different directions.Three sets of thoracic neurons were distinguished on the basis of latency. Type A interneurons had short latencies to wind stimuli (1.3–2.25 ms). Type B interneurons had longer latencies (4–6 ms), and motor neurons had the longest latencies (5.6–17.0 ms). Individual type A interneurons either responded equally to wind from all directions or were biased in their response. Directionality was related to the presence of ventral branches near one or both sides of the midline of the ganglion. Cells with ventral median (VM) branches on either side tended to be omnidirectional or front‐rear biased, whereas cells with VM branches on only one side were biased to that side. Although several type B interneurons had strong wind responses and were directionally sensitive, they did not have VM branches. We hypothesize that the presence of VM branches in type A interneurons permits connection with ventral giant interneurons, and this connection accounts for their short latency and directional properties. This hypothesis will be tested in the companio

ISSN:0022-3034    

DOI:10.1002/neu.480190702

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1988

数据来源: WILEY

摘要:

AbstractA number of thoracic interneurons (TIs) have been found to receive inputs from ventral giant interneurons (vGIs). Each of these cells responds to wind with short latency depolarizations. The previous paper described response properties of several TIs to wind stimuli, including those excited by vGIs. The data showed a correlation between the shape of the TI's wind fields and its morphology. The presence of ventral branches located near the midline of the ganglion predicts a strong response to wind on that side. These ventral median (VM) branches are in the proper location to permit overlap with processes from vGIs. Here we describe the patterns of connections between individual vGIs and 13 of the thoracic interneurons located in the meso‐ and metathoracic ganglia. A correlation was found between the presence of VM branches and excitation by vGIs. TIs were only excited by vGIs on the side(s) on which VM branches exist. However, presence of a VM branch does not imply that all vGIs on that side make connections with the TI.Summation was found between various vGIs that excited each individual thoracic interneuron. In unilateral thoracic interneurons, no sign of inhibition was found from vGIs on the sides opposite that which contained excitatory vGI axons. Neither was there any evidence of inhibition from dorsal giant interneurons. In addition preliminary evidence indicated that left‐right homologues do not inhibit one another. Thus, the data suggest that directional wind fields are primarily the result of selective connection from specific v

ISSN:0022-3034    

DOI:10.1002/neu.480190703

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1988

数据来源: WILEY

摘要:

AbstractThe rhythmical ciliary arrest behavior characteristic of the veliger larvae of the prosobranchCalliostoma ligatumdevelops in a predictable sequence of events. Spontaneous, small‐amplitude (1–3 mV) postsynaptic potentials (PSPs) are first recorded intracellularly from prototrochal ciliated cells at about 45 h after fertilization. Prototrochal ciliated cells, which are precusors of the locomotory, preoral ciliated cells of mature veligers, are electrically coupled to each other. Cilia beat continuously and erratically at this stage. PSP amplitude and duration gradually increase with age, and at about 56 h, preoral ciliated cells become electrically excitable. A single regenerative action potential first occurs at this time and causes a velum‐wide, ciliary arrest. Between 56 and 72 h, the duration of the depolarizing phase of the preoral ciliated cell action potential decreases, the amplitude increases, and the hyperpolarizing undershoot develops. Preoral ciliated cell action potentials appear to be Ca2+‐dependent throughout development. Shortening of the action potential duration and development of the hyperpolarizing undershoot may be due to activation of later developing K+channels. As veligers become competent to metamorphose, the preoral velar cells and their connections with the body dete

ISSN:0022-3034    

DOI:10.1002/neu.480190704

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1988

数据来源: WILEY

摘要:

AbstractTreatment of adult female canaries with testosterone (T) causes them to produce male‐typical vocalizations and results in striking growth of brain nuclei that control song behavior (Nottebohm, 1980). The song‐control nucleus HVc (caudal nucleus of the ventral hyperstriatum) contains cells that concentrate testosterone or its metabolites, suggesting that steroid hormones may induce the growth of HVc directly by regulating the expression of specific genes in those HVc neurons that have steroid receptors. However, we have previously provided evidence that is inconsistent with the idea that steroids promote growth of HVc solely via a direct action on hormone receptors: testosterone treatment of deafened adult females results in very little growth of HVc, relative to T‐treated hearing birds (Bottjer et al., 1986b). Thus, birds in the former group undergo very little overall growth of HVc despite high circulating levels of hormone. We show here that the slightly increased size of HVc in T‐treated deaf birds is attributable to an increase in neuronal spacing; the greatly increased size of HVc in T‐treated hearing birds is due to an increase in neuronal number as well as spacing. There was virtually no increase in number of HVc neurons in T‐treated deafened birds relative to control groups, whereas T‐treated hearing birds showed a marked increase in neuron number. The song‐control nucleus RA (robust nucleus of the archistriatum), which receives direct afferent input from HVc, also increases in size in response to testosterone treatment. However, the volume of RA increases in both hearing and deafened birds; this increase is primarily due to an increase in neuronal spacing as well as a small increase in neuron number. These results demonstrate that the number of neurons in a specific vocal‐control nucleus (HVc) can change dramatically in adult canaries and suggest that some synergistic action of hormonal and sensory stimulation is necessary to ind

ISSN:0022-3034    

DOI:10.1002/neu.480190705

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1988

数据来源: WILEY

摘要:

AbstractNovel chemical and electrical connections form between neurons not normally connected in the buccal ganglia of the snailHelisoma. We examined the cellular and environmental conditions required for the formation of each type of connection. Previous work in situ showed that novel electrical connections could form in response to axotomy. We have now found that axotomy can evoke the formation of novel unidirectional chemical connections between neurons B5 and B4 in addition to a novel electrical connection. The novel chemical connections display all of the normal properties of chemical synapses inHelisomaganglia. These connections, however, are transient in nature and break 4 days following axotomy.Previous work has shown that conjoint outgrowth is required for the formation of electrical connections. In cell culture we have investigated whether conjoint outgrowth is also required for chemical synaptogenesis. Using neurons B5 and B19 we have found that when neuron pairs make contact in cell culture, under conditions of synchronous neurite extension, both electrical and chemical synapses form. However, if one neuron has ceased extension prior to contact by a growing neuron, electrical synapses never form (Hadley et al., 1983, 1985) but chemical synapses do form. Furthermore, the addition of serotonin (10−6M) to culture medium to inhibit neurite extension of B19, but not that of B5, selectively prevents the formation of electrical connections while permitting the formation of chemical synapses. Thus, the timing of contact in relation to the state of neurite extension can specify the type of connection a given neuron can for

ISSN:0022-3034    

DOI:10.1002/neu.480190706

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1988

数据来源: WILEY

摘要:

AbstractCompetition among axon terminals is usually considered to contribute to the formation of patterned synaptic connections. During axonal regeneration of motor neurons in the cockroach, leg muscles initially become innervated by appropriate and inappropriate motor neurons. All axon terminals from inappropriate neurons eventually are eliminated, resulting in the reformation of the original innervation pattern. Destruction of an identified motor neuron by the intracellular injection of pronase did not prevent the eilimenation of inappropriate axon terminals in the muscle normally innervated by that motor neuron. Therefore, competition does not play a role in the reinnervation of the leg muscles. This indicates a major role for specific cell‐cell recognitio

ISSN:0022-3034    

DOI:10.1002/neu.480190707

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1988

数据来源: WILEY

ISSN:0022-3034    

DOI:10.1002/neu.480190701

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1988

数据来源: WILEY