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At least 19 recordsLinked to original sources
PubMed1978

Denervation of the primary olfactory pathway in mice. V. Long-term effect of intranasal ZnSO4 irrigation on behavior, biochemistry and morphology.

Intranasal irrigation of mice with 0.17 M ZnSO4 solution results in the immediate and total loss of the ability to find a buried food pellet. This anosmia persists for 6 weeks in at least 80% of the treated mice and for 4 months in half of the animals. This marked behavioral effect is matched by a long-term reduction of the levels of carnosine synthesis and transport in the primary olfactory pathway. These biochemical parameters are virtually undetectable at two weeks after treatment and even at one year after treatment do not exceed 5-10% of average control values. Light microscopic observations of tissues of the primary olfactory pathway at various times after treatment are consistent with these observations and indicate a substantial destruction of the olfactory epithelium with subsequent atrophy of the olfactory bulb. At very long intervals after treatment, some receptor regeneration is apparent with accompanying reinnervation of the olfactory bulb. Estimates from microscopy and biochemistry suggest that much less than 10% of the normal complement of functioning receptor cells is adequate to give apparently normal food-finding behavior.

Alanine↗
PubMedDate not supplied

Oestrogenic influences on the electrical activity of the olfactory pathway.

The influence of the oestrogenic hormones over the spontaneous and induced activity of the olfactory pathway was studied in normal female cats. Electrodes were placed chronically or acutely in the olfactory bulb (OB), olfactory tubercle (OT) and in the prepyriform cortex (PPC). Oestrogenic hormones were applied locally in the posterior hypothalamic region. Recordings were made during the two different phases of the oestral cycle. In addition, another group of castrated animals was studied. The oestral phase was induced in these cats by the subcutaneous administration of 17-beta-oestradiol. Results indicate that the pattern of the electroencephalographic spontaneous activity as well as the response induced by hypothalamic stimulation changed. The number of the bursts for each 10 sec trace was higher in oestrus than in anoestrus for all the structures studied. The duration of each burst also changed, being shorter in oestrus than in anoestrus cats. The threshold for significant bursting in the olfactory structures following hypothalamic stimulation was lower in oestrus than in anoestrus. The evoked potentials recorded in the same three olfactory structures by hypothalamic stimulation exhibited changes in correlation with the hormonal administration. In all the structures studied the amplitude of the different components of the evoked potentials increased immediately after the hormones were administered. However, the most dramatic increase was observed in the olfactory tubercle. In order to further investigate these changes in acute preparations, a study evaluating the excitability changes was conducted. Applied pulse pairs, with different interpulse intervals between 200 to 1000 msec, were delivered in the hypothalamus before and after 200 micrograms of the hormone were administered into the posterior hypothalamus.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1975

Denervation in the primary olfactory pathway of mice. II. Effects on carnosine and other amine compounds.

Carnosine (beta-alanyl-histidine) is present in the olfactory bulb and olfactory eqithelium of mice and rats at 1-2 nmole/mg tissue. Peripheral deafferentation or central denervation causes a rapid, selective decrease of this depeptide from the reciprocal portion of the primary olfactory pathway. These data demonstrate the localization of carnosine within the primary olfactory chemoreceptor neurons and suggest a possible role for this compound in neural transmission.

Alanine↗
PubMedDate not supplied

Olfactory pathway evoked potentials in response to hypothalamic stimulation.

Ipsilateral and contralateral stimulation of lateral, ventromedial and posterior hypothalamic nuclei produced evoked responses in the olfactory bulb and in the prepyriform cortex. No differences in the latencies were found by stimulation of each nucleus in the homo and contralateral olfactory structures. The high amplitude of the fast component (N1) was obtained with stimuli applied to the ventral zones and the slow components (N2, N3) were obtained with more dorsal stimulation. An ipsilateral pathway is indicated at the supramammillary and posterior commissure level, since severing these structures abolishes the evoked responses. A bilateral projection is proposed for the olfactory bulb.

Animals↗
PubMed1975

An olfactory projection area in orbitofrontal cortex of the monkey.

An olfactory projection area was studied in monkeys anesthetized with Nembutal. 1. Evoked potentials were recorded when the olfactory bulb (OB) was electrically stimulated in the lateroposterior portion of the orbitofrontal cortex (LPOF). However, those potentials disappeared when the anterior pyriform cortex (AP) (probably together with the medial portion of the amygdala (MA)) was aspirated or electrically destroyed. 2. In nearly the entire hypothalamic region, evoked potentials were recorded by the same stimulation of the OB. When the hypothalamic region was stimulated, evoked potentials were recorded in the LPOF. 3. The evoked potentials in the LPOF due to the OB stimulation never disappeared even when the thalamus was extensively aspirated or destroyed electrically, but they did disappear when the anterolateral and dorsoposterior portions of the hypothalamus were absorbed or electrocoagulated. 4. Evoked potentials in the mediodorsal nucleus (MD) of the thalamus were recorded when the OB was stimulated. When this nucleus was stimulated, evoked potentials were observed in the broad extent of the orbitofrontal cortex anterior to the LPOF, but never in the LPOF itself. 5. Monkeys were conditioned to discriminate two odors. When the LPOF was removed, such ability strikingly decreased; but when other areas in the prefrontal cortex were removed, the ability decreased only slightly. 6. It was concluded that there exists an olfactory pathway from the OB to the LPOF through the AP (and probably the MA) and the hypothalamus, but none through the thalamus, and that the LPOF plays an important role in the discrimination of odors. 7. It was proved that the entorhinal cortex (ER) is neither located as an intermediate olfactory area nor is it situated as a higher area than the LPOF in the newly found olfactory pathway stated above. It may be a link between the high olfactory area and the limbic system.

Animals↗
PubMed1979

Failure of deodorized males to induce oestrus in the wild mouse.

The ability of female mice to return to oestrus following exposure to males perfumed either with oil of wintergreen or with the commercial perfume, "Kanta" was evaluated. Unisexual grouping of female mice induced anoestrus in all individuals. Oestrus was, however, promptly induced in the majority of unisexually grouped females by exposure to normal males. By contrast, exposure to perfumed males failed to induce oestrus in unisexually grouped females. The results suggest that male urine which is the source of the primer pheromone involved in the induction of oestrus was ineffective because of the masking effect of artificial scents. Hence the unisexually grouped females were unable to perceive the pheromone from males and continued to remain in anoestrus following exposure to perfumed males. The results provide additional evidence in support of the view that the urinary pheromone produced by males induces oestrus in females by acting through olfactory pathways.

Animals↗
PubMed1979

Responses of olfactory bulb neurones to the dipeptide carnosine.

Carnosine has been applied by microiontophoresis ot identified neurones in the olfactory bulb of the rat from solutions of different pH. Although mainly without effect when compared with conventional excitatory and inhibitory amino acids, the dipeptide tended to be depressive when ejected as a cation and excitant when ejected as an anion. The results obtained are not in favour of this substance being an excitatory transmitter in the primary olfactory pathway.

Amino Acids↗
PubMed1979

The organization of feline entopenduncular nucleus projections: anatomical studies.

The organization of entopeduncular nucleus (EPN) projections was studied in cats using autoradiographic and horseradish peroxidase (HRP) techniques. In autoradiographic studies, EPN axons were found to terminate in a J-shpaed region in the dorsal and medial part of the ventral anterior nucleus (VA) and the rostral portion of the adjacent ventral lateral nucleus (VL). EPN axons also terminated in the rostral portion of the centrum medianum (CM), the ventrolateral portion of the lateral habenular nucleus (LHB), and the pedunculopontine nucleus (PP). The VA included the largest terminal field although the LHB had the greatest density of terminals. Regardless of the region of EPN into which amino acids were injected, the terminal fields were the same: there was no localization within the EPN of the cells projecting to one region. HRP-containing cells were distributed throughout the EPN following injections into the VA, LHB, or PP, although many more cells were labeled following injections into either VA or LHB than PP. EPN cells containing HRP following injections into either VA or LHB were not morphologically different from those not containing HRP in the same respective animals. Following HRP injections into stria medullaris, only cells in the rostral part of the EPN were labeled, providing evidence that rostrally and caudally located EPN neurons have different paths to LHB. Although there may be a rostrocaudal organization of pathways to LHB, individual regions of the nucleus project to the same areas.

Animals↗
PubMed1975

The efferent connections of the suprachiasmatic nucleus of the hypothalamus.

The efferent connections of the suprachiasmatic nucleus of the hypothalamus have been studied in the rat by the injection of 3H-proline into the nucleus and the surrounding regions of the rostral hypothalamus, and by the injection of the enzyme marker, horseradish peroxidase, into the region of the ventromedial hypothalamic nucleus. After an injection of 3H-proline confined to the ventral portion of the suprachiasmatic nucleus, transported label can be followed, in the autoradiographs, dorsally and caudally in the periventricular area as far as the caudal end of the ventromedial nucleus, into the triangular area between this nucleus and the arcuate nucleus, and along the ventral aspect of the tuberal region, just lateral to the ventromedial nucleus. A small number of silver grains are also seen over the internal lamina of the median eminence. No label can be followed rostrally or immediately lateral to the nucleus. Comparable injections into adjoining regions of the hypothalamus (especially the anterior hypothalamic area, the medial preoptic area, and the retrochiasmatic region) show transported label over the same regions, but with a somewhat different pattern of grain distribution; in addition, the anterior hypothalamic area shows an extensive projection through the medial forebrain bundle to the mammillary and supramammillary nuclei, the midbrain tegmentum, and certain of the midline thalamic nuclei. Although it is difficult in our autoradiographs to distinguish between the course of the efferent fibers from the suprachiasmatic nucleus and the zones in which they terminate, our evidence favors a termination among the cells of the periventricular area, and upon dendrites of the cells in the ventromedial, dorsomedial and arcuate nuclei, which extend beyond the limits of the nuclei into the periventricular area and to the area beneath the ventromedial nucleus.

Amygdala↗
PubMed1978

Association and commissural fiber systems of the olfactory cortex of the rat.

The association and commissural fiber systems arising in the olfactory cortical areas caudal to the olfactory peduncle (the piriform cortex, nucleus of the lateral olfactory tract, anterior cortical nucleus of the amygdala, periamygdaloid cortex and entorhinal cortex) have been studied utilizing horseradish peroxidase as both an anterograde and a retrograde axonal tracer. In the piriform cortex two sublaminae within layer II (IIa and IIb) layer III have been found to give rise to distinctly different projections. Retrograde cell labeling experiments indicate that the association fiber projection from layer IIb is predominatnly caudally directed, while the projection from layer III is predominantly rostrally directed. Cells in layer IIa project heavily to areas both caudal and rostral to the piriform cortex. The commissural fibers from the piriform cortex are largely restricted in their origin to layer IIb of the anterior part of the piriform cortex and in their termination on the contralteral side to the posterior part of the piriform cortex and adjacent olfactory cortical areas. A projection to the olfactory bulb has also been found to arise from cells in layers IIb and III of the ipsilateral piriform cortex, but not in layer IIa. In addition to those from the piriform cortex, association projections have also been found from other olfactory cortical areas. The nucleus of the lateral olfactory tract has a heavy bilateral projection to the medial part of the anterior piriform cortex and the lateral part of the olfactory tubercle (as well as a lighter projection to the olfactory bulb); both the anterior cortical nucleus of the amygdala and the periamygdaloid cortex project ipsilaterally to several olfactory cortical areas. The entorhinal cortex has been found to project to the medial parts of the olfactory tubercle and the olfactory peduncle. The olfactory tubercle is the only olfactory cortical area from which no association fiber systems (instrinsic or extrinsic) have been found to originate. A broad topographic organization exists in the distribution of the fibers from several of the olfactory areas. This is most obvious in the anterior part of the olfactory cortex, in which fibers from the more rostral areas (the anterior olfactory nucleus and the anterior piriform cortex) terminate in regions near the lateral olfactory tract, while those from more caudal areas (the posterior piriform cortex and the entorhinal cortex) terminate in areas further removed, both laterally and medially, from the tract. Projection to olfactory areas from the hypothalamus, thalamus, diagonal band, and biogenic amine cell groups have been briefly described.

Animals↗
PubMed1978

The luteinizing hormone-releasing hormone (LH-RH) neuronal networks of the guinea pig brain. I. Intra- and extra-hypothalamic projections.

In the guinea pig brain, LH-RH-containing cell bodies are located not only within the classical hypophysiotrophic area but also in the medial preoptic area, septum and olfactory tubercle. LH-RH fiber tracts project not only to the primary portal plexus in the median eminence but also throughout the limbic forebrain and limbic midbrain regions. Using radiofrequency lesions in different brain regions, the projections of LH-RH cell bodies were determined. Cells in the medial preoptic area project ot the organum vasculosum of the lamina terminalis (OVLT), the suprachiasmatic nucleus, the mammillary body complex and the ventral tegmental area. LH-RH neurons in both the medial septal nucleus and medial preoptic area project via the stria medullaris to the medial habenular nucleus and from there via the fasciculus retroflexus to the interpeduncular nucleus of the midbrain. Other LH-RH neurons in the medial septal nucleus, nucleus of the diagonal band of Broca and olfactory tubercle are congregated in small clusters around large blood vessels which penetrate into this area, and they do not appear to send axons outside their immediate vicinity. The types of LH-RH axonal terminations and the roles of these peptide-containing neurons are discussed.

Animals↗
PubMed1979

Morphine and naloxone effects on olfactory evoked electrographic activity in the amygdala.

This research tested morphine and naloxone effects on evoked EEG and unit activity in 3 opiate-relevant brain areas in response to electrical stimulation of the olfactory bulb in acute, unanesthesized rat preparations. Stimulation evoked clear EEG responses in the amygdala (Amyg) and sometimes in the other areas (caudate and central grey); morphine (15 mg/kg) depressed the Amyg response in some rats, but enhanced it in others, and naloxone usually reversed both kinds of effect. Stimulation caused excitatory unit impulse reponses in the Amyg, and morphine unexpectedly increased the magnitude of the stimulus-evoked excitation; naloxone reversed this enhancement. In control rats, naloxone often decreased the Amyg evoked response. Stimulus-evoked increases in unit activity in the caudate and central grey, when they did occur, were depressed by morphine, but naxoxone had no consistent reversing effect. Both the EEG and unit data indicate that morphine excites, or disinhibits, certain neurons associated with the olfactory-Amyg pathway. There was also some evidence that this pathway contains endorphinergic elements.

Amygdala↗