Judith R. Ganchrow

Neonatal facial expressions in response to different qualities and intensities of gustatory stimuli

Facial expressions of 23 neonates were analyzed for specific features following oral stimulation with distilled water, 0.1 and 1.0 M sucrose, 0.15 and 0.25 M urea, and 0.0001 M quinine hydrochloride. Responses were videotaped and later decoded in a double-blind setting. While some features were present for all stimulations, other components were consistently associated with a specific taste quality. Within a quality, increasing the concentration elevated the incidence of features associated with that quality. Estimates of magnitude and hedonic tone conveyed by the total facial response to each stimulus suggested that the face was, within limits, an accurate reflection of stimulus quality and intensity.

Classical conditioning in newborn humans 2–48 hours of age

Classical conditioning was studied in newborn humans 2–48 hours of age. Infants in the Experimental group received 18, 2-min conditioning trials, each consisting of 10 s of gentle forehead stroking followed immediately by midline intraoral delivery of 0.2 ml 12.5% (0.037 M) sucrose solution via pipette. Sucrose delivery for infants in one control group was delayed following stroking by intervals of 10, 20, or 30 s presented randomly. Infants in the second control group were not stroked but only received sucrose on each trial. Immediately following the 18 sucrose trials, all infants received 9, 1-min extinction trials which consisted exclusively of 10 s of forehead stroking with no other manipulations during the remaining 50 s. All sessions were video-recorded and analyzed at a later date, with special attention paid to head-orienting, sucking, and crying behaviors. Only infants in the Experimental group presented evidence for classical conditioning. Relative to infants in the first control group, they emitted many more head-orient and sucking responses during the 10-s stroking intervals. Moreover, they exhibited a classic extinction function to stroking in sucrose absence. Finally, 7 of 8 Experimental infants cried during extinction, whereas only 1 of 16 Control infants cried. These findings demonstrate the ability of human newborn infants to extract predictability between two related events and that this form of conditioning is strongly affective. Implications for early mother-infant bond development are discussed.

Influence of intake of sweet solutions on the analgesic effect of a low dose of morphine in randomly bred rats

The time course for the development of morphine tolerance, following prolonged sweet intake, was examined in randomly bred Sabra rats. Exposure to 3% glucose in 6 mM saccharin solution increased drinking by about three times as compared to rats supplied only with water. Suppression of the analgesic effect of morphine was already detectable after 24 h of intake and became progressively more marked within the next 5 weeks. These results support an active interaction between sweet consumption and endogenous opioids in randomly bred rats.

Number and distribution of taste buds in the oral cavity of hatchling chicks

The location and number of taste buds were mapped in palatal epithelia of one-day old chicks and bud widths measured. Bud counts additionally were recorded for the tongue, and floor of the lower beak. An average of 316 taste buds was observed in the oral cavity of which 69%, 29% and 2% were distributed across oral epithelium in the upper beak (palate), lower beak and posteroventrolateral region of the anterior tongue, respectively. In each oral region, salivary gland ducts lying adjacent as well as gland ductules penetrating through the buds were prevalent. This relation may provide the bio-fluid milieu for receptor stimulation during feeding. Widths of palatal buds were bimodally distributed, peaking at diameters between 40-49 and 60-69 microns. The taste bud-rich oral epithelium in these one-day old chicks is consonant with their precocial nature. The topographic distribution of taste buds appears to be in register with those regions of epithelium contacted by food which is transported anteroposteriorly through the oral cavity by the chickens prehensile tongue.

Organization of geniculate and trigeminal ganglion cells innervating single fungiform taste papillae: a study with tetramethylrhodamine dextran amine labeling

Single gustatory nerve fibers branch and innervate several taste buds. In turn, individual taste buds may receive innervation from numerous gustatory nerve fibers. To evaluate the pattern of sensory innervation of fungiform papilla-bearing taste buds, we used iontophoretic fluorescent injection to retrogradely label the fibers that innervate single taste papillae in the hamster. For each animal, a single taste papilla was injected through the gemmal pore with 3.3% tetramethylrhodamine dextran amine. Fungiform papillae either at the tongue tip (0.5-1.5 mm from the tip) or more posteriorly (1.5-3.0 mm from the tip) were injected. After one to seven days survival, the geniculate and trigeminal ganglia and the tongue were sectioned and examined for labeled cells and fibers, respectively. Analysis of the number and topographic distribution of geniculate cells innervating single taste papillae, shows that: (i) 15 +/- 4 (S.D.) ganglion cells converge to innervate a single fungiform taste bud; (ii) more ganglion cells innervate anterior- (range: 13-35 cells) than posterior-lying buds (range: five to 12 cells), which, in part, may be related to bud volume (microm3); and (iii) ganglion somata innervating a single taste bud are scattered widely within the geniculate ganglion. Analysis of labeled fibers in the tongue demonstrated that two to eight taste buds located within 2 mm of the injected taste bud share collateral innervation with the injected taste bud. Since all buds with labeled fibers were located in close proximity (within a 2-mm radius), widely dispersed geniculate ganglion cells converge to innervate closely spaced fungiform taste buds. Trigeminal ganglion (mandibular division) cells were also labeled in every case and, as with the geniculate ganglion, a dispersed cell body location and collateralization pattern among papillae were observed. This study shows that iontophoresis of tetramethylrhodamine dextran amine, selectively applied to individual peripheral receptor end-organs, effectively locates sensory ganglion cells in two different ganglia that project to these sites. Moreover, the marker demonstrates collateral branches of sensory afferents associated with the labeled fibers and the nearby receptor areas innervated by these collaterals. The labeling of single or clusters of receptor cells, as well as identified sensory afferents, affords future possibilities for combining this technique with immunocytochemistry to establish the relationships of innervation patterns with neurotransmitters and neurotropic substances within identified cells.

Consummatory responses to taste stimuli in rats selected for high and low rates of self-stimulation

Abstract The factors mediating self-stimulation are often considered to coincide with those initiating and maintaining avid intake of sweet-tasting substances. The availability of two populations of albino rats (LC1 and LC2), each genetically selected for high- and low-self-stimulators, provided an opportunity to test this hypothesis. Consummatory responses of these 4 lines were investigated using a 24-hr two-bottle test. Seven concentrations of sodium saccharin, as well as 8 concentrations of quinine hydrochloride, were each presented against water in a double-blind setting. Lateral hypothalamic self-stimulation rates were then determined. It was found that the population (LC2) exhibiting the largest separation of high and low self-stimulation rates, also was separated most by saccharin solution intakes: The genetically high ICSS responders consumed the most—while the genetically low ICSS responders of that population drank the least—saccharin solution across concentrations. In contrast, the effect of genetic line on quinine intake was minimal. Sex was a relevant variable with the females consuming relatively more saccharin solution and bar pressing at higher rates for self-stimulation, than males in each population. On the other hand, there was a tendency for the females of each line to be less rejecting of quinine solutions than males.

Brain‐derived neurotrophic factor‐, neurotrophin‐3‐, and tyrosine kinase receptor‐like immunoreactivity in lingual taste bud fields of mature hamster

The neurotrophins brain‐derived neurotrophic factor (BDNF) and neurotrophin‐3 (NT‐3), as well as their respective tyrosine kinase (Trk) receptors, TrkB and TrkC, influence peripheral target cell innervation, survival, and proliferation. In the mature taste system the role of neurotrophins and their receptors is not known. The mature hamster is an intriguing model because anterior lingual fungiform, unlike posterior lingual foliate and circumvallate, taste buds survive denervation. In light of this difference, we examined whether the degree of neurotrophin‐ or neurotrophin receptor‐like immunoreactivity (IR) normally differs among lingual gemmal fields. In single‐ and double‐labeled immunofluorescent experiments, 3,209 taste bud sections (profiles) from 13 hamsters were examined for immunopositive gemmal cells or nerve fibers using antibodies to BDNF and NT‐3, their respective receptors TrkB and TrkC, and the neural marker ubiquitin c‐terminal hydrolase L‐1 [protein gene product (PGP) 9.5]. In each gemmal field, more than 75% of taste bud profiles showed immunopositivity to BDNF, NT‐3, and TrkB. Across bud fields, BDNF‐, TrkB‐, and BDNF/TrkB‐like IR, as well as PGP 9.5 and PGP 9.5/BDNF‐like IR in centrally located, fungiform bud cells was greater (P < 0.0001 to P < 0.002) than in circumvallate or foliate buds. Within bud fields, the number of BDNF‐like, labeled bud cells/bud profile was greater than that for NT‐3‐like IR in fungiform (P < 0.0002) and foliate (P < 0.0001) buds. TrkC was immunonegative in gemmal cells. The average density of TrkB‐ and TrkC‐like fiber IR was more pronounced in fungiform than posterior gemmal‐bearing papillae. Thus, fungiform papillae, whose taste buds are least affected by denervation, exhibit specific neurotrophin and receptor enrichment. J. Comp. Neurol. 455:11–24, 2003.

Brain-derived neurotrophic factor-, neurotrophin-3-, and tyrosine kinase receptor-like immunoreactivity in lingual taste bud fields of mature hamster after sensory denervation

Unlike lingual taste buds in most mammals, fungiform buds on the anterior tongue of mature hamster survive sensory denervation. The role of the neurotrophin ligands, brain‐derived neurotrophic factor (BDNF) and neurotrophin‐3 (NT‐3), and their respective tyrosine kinase (Trk) receptors, TrkB and TrkC, in denervated taste buds is not known. The present report investigates changes in the degree of gemmal cell immunoreactivity (IR) (i.e., number of immunoreactive cells/bud profile) and density of nerve fiber‐IR of these markers in unilaterally denervated mature hamsters. The fungiform bud field after chorda tympani/lingual nerve resection is compared with the nerve‐dependent, posterior tongue foliate and circumvallate bud fields after glossopharyngeal nerve resection. Four weeks post lesion, the number of denervated fungiform buds matched that on the unoperated side, whereas denervated foliate and circumvallate bud counts decreased by 72% and 38%, respectively. In taste buds that survived on the posterior tongue, the degree of foliate bud cell BDNF‐, NT‐3‐, and TrkB‐like IR, and circumvallate bud cell BDNF‐ and NT‐3‐like IR, significantly decreased compared with the unoperated side. In contrast, for anterior tongue fungiform bud cells, the degree of neurotrophin‐ and receptor‐like IR was relatively less affected: NT‐3‐ and TrkB‐like IR were unchanged; BDNF‐like IR, although significantly decreased, was also maintained. Moreover, TrkB‐like fiber IR was essentially eliminated within and surrounding fungiform buds. Hence, NT‐3‐, BDNF‐, and TrkB‐like IR in fungiform gemmal cells may reflect an autocrine capacity promoting survival. Because TrkC‐like IR in bud cells is absent (i.e., immunonegative), and sparse in fibers intragemmally and perigemmally, NT‐3 may also bind to bud cell TrkB so as to sustain fungiform gemmal cell viability post denervation. J. Comp. Neurol. 455:25–39, 2003.

Nucleus of the solitary tract in the C57BL/6J mouse: Subnuclear parcellation, chorda tympani nerve projections, and brainstem connections: Mouse NST atlas and connections

The nucleus of the solitary tract (NST) processes gustatory and related somatosensory information rostrally and general viscerosensory information caudally. To compare its connections with those of other rodents, this study in the C57BL/6J mouse provides a subnuclear cytoarchitectonic parcellation (Nissl stain) of the NST into rostral, intermediate, and caudal divisions. Subnuclei are further characterized by NADPH staining and P2X2 immunoreactivity (IR). Cholera toxin subunit B (CTb) labeling revealed those NST subnuclei receiving chorda tympani nerve (CT) afferents, those connecting with the parabrachial nucleus (PBN) and reticular formation (RF), and those interconnecting NST subnuclei. CT terminals are densest in the rostral central (RC) and medial (M) subnuclei; less dense in the rostral lateral (RL) subnucleus; and sparse in the ventral (V), ventral lateral (VL), and central lateral (CL) subnuclei. CTb injection into the PBN retrogradely labels cells in the aforementioned subnuclei; RC and M providing the largest source of PBN projection neurons. Pontine efferent axons terminate mainly in V and rostral medial (RM) subnuclei. CTb injection into the medullary RF labels cells and axonal endings predominantly in V at rostral and intermediate NST levels. Small CTb injections within the NST label extensive projections from the rostral division to caudal subnuclei. Projections from the caudal division primarily interconnect subnuclei confined to the caudal division of the NST; they also connect with the area postrema. P2X2-IR identifies probable vagal nerve terminals in the central (Ce) subnucleus in the intermediate/caudal NST. Ce also shows intense NADPH staining and does not project to the PBN. J. Comp. Neurol. 522:1565–1596, 2014.

Olfactory function following late repair of choanal atresia

Results of olfactory function tests (threshold determination and odor identification) in three cases of bilateral and one case of unilateral choanal atresia are reported. All four patients underwent successful repair of choanal atresia at relatively advanced ages (8 to 31 years). Test results showed that patients who had suffered from bilateral atresia had permanent olfactory deficits, while the patient who had suffered from unilateral atresia appeared to have normal olfactory acuity. Although these results should be interpreted with caution due to the small number of cases examined, they suggest the possibility that early sensory exposure might be needed for the normal development of central olfactory functions in analogy to the visual system.