Abstract: The afferent connections of the main and accessory olfactory bulbs in the rat were examined by injecting horseradish peroxidase (HRP) into one or the other of these structures either by microelectrophoresis or by hydraulic pressure. Alternate sections were stained with newly developed HRP-procedures using either benzidine dihydrochloride (de Olmos and Heimer, '77) or tetramethyl-benzidine. Eighteen to twenty-four hours after unilateral HRP injections confined to the main olfactory bulb, a large number of HRP-labeled perikaria appeared in the following telencephalic structures on the ipsilateral side: All portions of the anterior olfactory nucleus (AON) except its external part, the lateral transitional field (LT) between AON and the paleocortex, the whole extent of the primary olfactory cortex (POC); The medial forebrain bundle area deep to the olfactory tubercle, the nucleus of the horizontal limb of the diagonal band (NHDB) and the nucleus of the lateral olfactory tract (NLOT). A moderate to small number of labeled cells, furthermore, were seen in the dorsal (DT) and medial (MT) transition fields, the ventral praecommissural hippocampus (tt2), the ventral superficial part of the nucleus of the vertical limb of the diagonal band (NVDB), the sublenticular part of the substantia innominata (SI), the anterior amygdaloid area, the posterolateral cortical amygdaloid nucleus (C2) and the transition region (28 L') between the olfactory cortex and the lateral entorhinal area proper. On the contralateral side a large number of labeled cells were found in all parts of the AON, with especially heavy labeling in its external part. A moderate number of labeled cells could also be detected in the lateral transition field (LT) and the NLOT. In the diencephalon and the brain stem a moderate number of HRP-labeled perikaria were observed in the dorsal, perifornical, and lateral hypothalamus, as well as in locus coeruleus and the dorsal and medial raphae nuclei. Following large HRP injections in the main olfactory bulb a moderate to small number of labeled cells were seen also in the posterior and premammillary hypothalamus and in field CA1 of the retrocommissural hippocampus on the ipsilateral side, as well as in POC on the contralateral side. It is possible, however, that the uptake of label took place in an undetected pool of HRP in the very rostral part of AON rather than in the olfactory bulb. HRP injections in the accessory olfactory bulb resulted in labeled neurons in the posterior ventro-lateral part of the bed nucleus of the stria terminalis, the nucleus of the accessory olfactory tract, the rostrodorsal portions of the medial amygdaloid nucleus, and whole extent of the posteromedial cortical amygdaloid nucleus (C3) on the ipsilateral side. A few lightly labeled cells were seen also in the contralateral C3.

Abstract: The olfactory system has been long reported as one of the most phylogenetically primitive (Ariens Kappers et al., 1967), because of the peripheral location of its neurons and the relatively conspicuous development in lower vertebrates

Abstract: The structure and connections of areas within the olfactory peduncle (anterior olfactory nucleus and tenia tecta) have been examined. The anterior olfactory nucleus has been divided into external, lateral, dorsal, medial, and ventro-posterior parts. In spite of the term nucleus which is applied to these areas, all of them contain pyramidal-type cells with apical and basal dendrites oriented normal to the surface, and are essentially cortical in organization. Experiments utilizing retrograde and anterograde axonal transport of horseradish peroxidase (HRP) have demonstrated that each of these parts of the anterior olfactory nucleus possesses a unique pattern of afferent and efferent connections with other olfactory areas. All subdivisions have projections to both the ipsilateral and contralateral sides, although the ipsilateral projection of the pars externa (to the olfactory bulb) is extremely light. Interestingly, crossed projections are in each case directed predominantly to areas adjacent to the homotopic areas. Two primary subdivisions may also be distinguished in the tenia tecta: a dorsal part composed largely of tightly packed neurons which closely resemble the granule cells of the dentate gyrus (bushy apical but no basal dendrites) and a ventral part which contains predominantly pyramidal-type cells. The connections of these two parts are also very different. The ventral tenia tecta receives substantial projections from the olfactory bulb, pars lateralis of the anterior olfactory nucleus, piriform cortex and lateral entorhinal area. It gives off a heavy return projection to the pars lateralis and lighter projections to the olfactory bulb, piriform cortex and olfactory tubercle. The dorsal tenia tecta receives a heavy projection from the piriform cortex, but none from the olfactory bulb. A few cells in the dorsal tenia tecta are retrogradely labeled from HRP injections into the medial aspect of the olfactory peduncle (involving the ventral tenia tecta and adjacent areas), but none are labeled from the other olfactory areas that have been injected. An area on the dorsal aspect of the olfactory peduncle that differs significantly from the anterior olfactory nucleus, tenia tecta and piriform cortex in terms of its connections and cytoarchitecture has been termed the dorsal peduncular cortex. The most striking feature of this area is its very heavy reciprocal connection with the entorhinal cortex, although it is also reciprocally connected with the olfactory bulb and piriform cortex and projects to the olfactory tubercle. Cells in layer I of the medial and ventral aspects of the olfactory peduncle have been retrogradely labeled from HRP injections into the olfactory tubercle and lateral hypothalamic area. These cells overlie the ventral tenia tecta, medial part of the anterior piriform cortex and pars ventro-posterior and pars lateralis of the anterior olfactory nucleus, but do not appear to be distributed in relation to the cytoarchitectonic boundaries. Possible functional roles of the areas within the olfactory peduncle have been discussed.

Abstract: 1 Development of Sensory Systems in Arthropods.- 2 Continuous Nerve Cell Renewal in the Olfactory System.- 3 The Interactions of Periphery and Center in the Development of Dorsal Root Ganglia.- 4 Visual Behavior Development in Nonmammalian Vertebrates.- 5 Ontogeny of Structure and Function in the Vertebrates Auditory System.- 6 The Development of Somatosensory Thalamus in Mammals.- 7 Functional Modification of the Developing Visual System.- 8 Development of Cutaneous Sensory Receptors in Birds.- 9 Cell Death During Development of the Nervous System.- Author Index.

Abstract: EXPOSURE to urine has been shown to influence the reproductive physiology of immature and mature female rodents. It affects the onset of puberty, as measured by vaginal opening1,2 and by uterine growth3,4, and the maintenance of pregnancy in mice5–7, as well as the timing of oestrous cycles in both mice8,9 and rats10,11. These effects seem to be elicited differentially by particular components of urine3. Although an ovulatory cycle eventually follows exposure to urine in all these examples12, reflex ovulation (that is, ovulation occurring shortly after brief exposure to a sensory stimulus) in response to male urine, has not been demonstrated previously. Also, traditionally, behavioural, as well as gonadal effects of urine were assumed to occur through the primary olfactory system4,12, rather than through one of the accessory olfactory systems, such as the vomeronasal system13–16. However, a role for the vomeronasal system was recently found for male hamster mating behaviour17. Furthermore, Raisman has pointed out that the vomeronasal system is brought into relationship with neural systems that are of importance in gonadotrophic release as well as sexual behaviour18. We demonstrate here that male urinary factors can elicit reflex ovulation in rats in the absence of coitus, mounting or removal to a novel cage. The present study is also the first to suggest that the vomeronasal system (in addition to, or instead of, the primary olfactory system) is involved in the effects of urinary chemicals on gonadal function.

Abstract: 1. Stable intracellular recordings were obtained from neurones in slices of the guinea-pig olfactory cortex maintained in vitro. 2. Single stimuli applied to the lateral olfactory tract (l.o.t.) produced an excitatory post-synaptic potential (e.p.s.p.) usually generating a single spike. 3. The e.p.s.p. was followed by a long (200-500 msec) after-depolarization (l.a.d.) of peak amplitude 5-16 mV. This was accompanied by a very large conductance increase and was associated with an inhibition of the intracellularly recorded e.p.s.p. and of spike generation. 4. The l.a.d. was more susceptible than the e.p.s.p. to depression by (i) repetitive l.o.t. stimulation and (ii) raising external [Mg2+]. The l.a.d. could be generated without a preceding spike. 5. At an average resting membrane potential of -74 mV the average reversal potential for the l.a.d. (El.a.d.) was -63 mV.El.a.d. became more positive on reducing [Cl-]out or on using KCl-filled electrodes. 6. It is concluded that the l.a.d. represents a Cl- -mediated inhibitory post-synaptic potential, generated through deep-lying recurrent inhibitory loops.

Abstract: Electrophysiological methods were used to examine the effectiveness of food odors in stimulating different olfactory receptor types inPeriplaneta

Abstract: The olfactory system of the pigeon (Columba livia) was examined. Our electrophysiological and experimental neuroanatomical (Fink-Heimer technique) data showed that axons from the olfactory bulb terminated in both sides of the forebrain. The cortex prepiriformis (olfactory cortex), the hyperstriatum ventrale and the lobus parolfactorius comprised the uncrossed terminal field. The crossed field included the paleostriatum primitivum and the caudal portion of the lobus parolfactorius, areas which were reached through the anterior commissure. In this report the relationships between areas that receive olfactory information and the possible roles that olfaction plays in the birds' behavior are discussed.

Abstract: 1. Physiological and behavioral experiments demonstrate an acute sensitivity of the olfactory system of sockeye salmon (Oncorhynchus nerka) to calcium ions. 2. Gross-potential (olfactory EEG) responses were reliably elicited by calcium at 5 × 10−6 M (a concentration well below the range found in natural fresh waters) and most animals responded differentially to calcium concentrations throughout the natural water range. 3. Mitral cell and granule layer cells of the olfactory bulbs responded to concentrations as low as 1 × 10−6 M CaCl2. Responses in each case were ion-specific. 4. In addition, behavioral experiments demonstrated that unconditioned sockeye fry would discriminate between 2 natural waters that differed only in calcium concentration (Table 1). 5. It is proposed that salmon recognize individual natural waters on the basis of the characteristic combination of odorants present and that calcium is one of these important odorant components. 6. The fact that large synchronous wave EEG responses induced by natural waters following distilled water are largely attributable to the calcium ions present (Fig. 7) may be important for the interpretation of earlier EEG studies of salmon homing.

Abstract: 1. Field potentials were evoked in slices of rat olfactory cortex by stimulating the lateral olfactory tract. In addition to previously described components of the wave-form, a further distinct surface-negative potential of low amplitude and long duration (I-wave) has been described. 2. Pentobarbitone, at concentrations of 10(-5) M and above, markedly enhanced enhanced the amplitude and duration of the I-wave with only minimal effect on other components of the field potential. 3. The I-wave was reversibly reduced by the GABA antagonists bicuculline and picrotoxin and was also attenuated at rapid rates of stimulation. Low chloride medium usually caused a transient increase in amplitude of the I-wave followed by a gradual reduction, suggesting that a chloride-mediated depolarization was involved. 4. Evoked inhibition, which was most probably post-synaptic, occurred in parallel with the I-wave. This was monitored as a suppression of, or increase in latency of the population spike evoked by a second stimulus at appropriate intervals after the first. Pentobarbitone substantially increased the duration of the post-synpatic inhibition, without obvious changes in the presynaptic inhibitory phenomenon associated with antidromic firing in the lateral olfactory tract. 5. It is proposed that the I-wave is the field potential representation of a population depolarizing i.p.s.p. and that the main action of pentobarbitone is to enhance this inhibition.

Abstract: Publisher Summary This chapter discusses the effects of olfactory deprivation during the postnatal period on the morphological and neurochemical features of the developing rat olfactory bulb. Each olfactory bulb receives its entire afferent input solely from its ipsilateral olfactory mucosa. This anatomical situation provides an ideal system, where the effects of unilateral olfactory deprivation on the ipsilateral olfactory bulb may be properly compared with its control counterpart—that is, the contralateral bulb. The chapter argues that the developing olfactory bulb of the rat is a suitable model for studies on the central neural correlates of early sensory deprivation and shows that early olfactory deprivation in this animal, whether produced by unilateral neonatal closure of one nostril or bilateral chemical destruction of olfactory receptor neurons, leads to marked reduction in the growth of the olfactory bulb, accompanied by a state of chemical underdevelopment and anatomic atrophy. Specifically, early olfactory deprivation causes significant reductions in weight, total protein, DNA, RNA, and Na,KATPase and acetylcholinesterase activities, as well as a marked reduction in the total number of mitral and tufted cells. It is suggested that during postnatal development, the presence of olfactory receptor activity is necessary for the proper development of the olfactory bulbs.

Abstract: The peripheral olfactory organs of Anguilla japonica, Conger myriaster, Microdonophis erabo, Gymnothorax kikado (Anguilliformes) and Trachinocephalus myops (Myctophiformes) were examined by scanning electron microscopy. In four species of the Anguilliformes, the olfactory rosette is very elongate in shape and consists of a large number (100--130) of lamellae. Almost whole surface of the lamellae is covered uniformly with dense cilia which arise mostly from type 1 ciliated cells (cells giving off many long cilia from the flat and wide surface). The type 2 ciliated cells (cells protruding a hillock-like cell apex from which several cilia project radially) and the microvillous cells (cells bearing many microvilli in a tuft) are present under the dense cilia. The rod cells (cells protruding a simple rod) occur singly or in groups. In Trachinocephalus myops, the peripheral olfactory organ consists of 8-10 lamellae which are arranged in the shape of a fan. On each face of the lamellae, a broad non-ciliated zone along the distal margin of the lamella (indifferent epithelium) surrounds a central ciliated region (sensory epithelium). In the sensory epithelium, the type 1 ciliated cells, type 2 ciliated cells and microvillous cells are scattered evenly but rather sparsely.

Abstract: The peripheral olfactory organs of four species of Gasterosteiformes, one species of Channi-formes and one species of Synbranchiformes were examined by means of scanning electron micro-scopy. In the olfactory lamellae of Pungitius pungitius and Fistularia petimba (Gasterosteiformes), the sensory epithelium is dispersed in many islets surrounded by the indifferent epithelium. In the sensory islets of P. pungitius, type 2 ciliated cells and microvillous cells are present densely, but in F. petimba, type 1 and type 2 ciliated cells, microvillous cells and rod cells are present very sparsely. The olfactory organ of Syngnathus schlegeli and Hippocampus coronatus (Gasterosteiformes) has no lamelliform structure. Type 1 and type 2 ciliated cells and microvillous cells are scattered evenly but sparsely in the flat bottom of the nasal sac. In Channa maculata (Channiformes), type 1 and type 2 ciliated cells and microvillous cells cover uniformly and rather densely the whole surface of the olfactory lamellae which are arranged parallel to the rostro-caudal axis of the fish. Rod cells occur in groups. In Fluta alba (Synbranchiformes), the olfactory organ has no lamelliform structure. Type 2 ciliated cells cover densely the inner wall of the tubular nasal sac. A small number of type 1 ciliated cells and microvillous cells are also present.

Abstract: A well-differentiated olfactory neuroepithelioma was found protruding from the left olfactory fossa of a 6-year-old domestic multicolored carp, Cyprinus carpio . Following diagnostic biopsy the neoplasm continued to grow. At necropsy, the tumor was found to extend beyond the olfactory chamber into the intracranial portion of the olfactory bulb, but no distant metastases could be detected. Histologically, the neoplasm had a remarkably organoid appearance, being composed of imperfect reproductions of the normal olfactory organ including olfactory membrane, axonal bundles, and glial tissue. Electron microscopy demonstrated the presence of numerous ciliated olfactory sensory cells as well as sustentacular, mucous, and basal cells within the neoplastic simulations of olfactory membrane. These observations, together with those from two previous case reports of olfactory neuroepitheliomas in teleosts, suggest that this type of tumor tends to be more highly differentiated than are neoplasms of similar origin in mammals.

Abstract: Experiments were done to elucidate properties of the late N-wave which was induced in vitro in thin sections of the olfactory cortex of the rat in response to stimulation of the lateral olfactory tract. The late N-wave decreased in size at a stimulation rate of more than once every 90 sec or at temperatures higher than 27°C. The late N-wave was suppressed in the presence of GABA, picrotoxin or bicuculline or in the Clfree medium. Penicillin or pentylenetetrazol, which blocked actions of GABA on the presynaptic potential, also suppressed the late N-wave. The late N-wave first appeared at postnatal ages of 18-25 days. The late N-wave reversed in polarity when recorded from the deep layers of the sections or from the cut surface of the sections. Single cells in the deep portions of the sections discharged during the late N-wave. Cells in the superficial layers fired just before or after the late N-wave. In order to explain these observations, a neuronal model for generation of the late N-wave was presented.

Abstract: SUMMARY The phreatic, anophthalmic fish Uegitglanis zammaranoi Gianferrari (Claridae Siluriformes) from Somalia has anterior narices covered with a flap and posterior narices. The major axis of the olfactory rosette parallels the longitudinal axis of the body, thus the direction of movement of the fish. This seems to be due to the differing rapport assumed by some cranial bones in adapting to phreatic life. According to the mean number of rosette lamellae (21) and neurons per mm2 of neuroepithelial surface (65,000), Uegitglanis can be classified as medially macrosmatic. Light and electron microscope studies did not reveal any substantial differences between the olfactory organ and the typical aspect of this organ in various other vertebrates. Characteristic of the species is the olfactory vesicle, often gutter shaped, which does not surpass the epithelial surface. Cilia and microvilli are present in all the sensory and some supporting cells. Differentiating elements rich in vesicular ergastoplasm are inte...