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S R Robinson

Publications and source records attributed to S R Robinson.

At least 91 records · Page 5Linked to original sources
PubMed1992

Prenatal experience with milk: fetal behavior and endogenous opioid systems.

The existence of organized responses to milk in newborn mammals, which lack experience at the nipple, implies the prenatal development of neural and behavioral systems for recognizing, obtaining, and processing milk. Many components of milk-directed behavior have been identified in the fetus. The stretch response expressed by neonatal rats during milk ejection at the nipple can be elicited before birth by infusing milk into the mouth of the fetus. Milk promotes reorganization of fetal motor behavior, facilitates expression of the stretch response, and alters fetal responsiveness to cutaneous stimulation. Pretreatment of fetuses with opioid agonists and antagonists has confirmed involvement of the mu and kappa opioid systems in mediating the effects of milk. Opioids appear to play a dual role in milk-oriented behavior: Initially, opioids suppress behavioral responses of the fetus and neonate to novelty, permitting ingestion of milk, and secondarily, opioid activity can promote learning at the nipple by functioning as a reinforcer. Study of milk-directed behavior in the fetus may promote better understanding of the special needs of preterm human infants.

Animals↗
PubMed1992

Kappa opioid mediation of fetal responses to milk.

A series of experiments provided evidence for the existence of a functional opioid system in the fetal rat near term. Application of a tactile probe to the perioral region of the fetus consistently evoked a stereotypic facial wiping response. Administration of low dosages of morphine to the fetus had little effect on nonevoked motor activity but reduced fetal responsiveness to cutaneous stimulation. Milk infused into the mouth of the fetus reduced fetal responsiveness to the tactile probe. Milk's effect on cutaneous responsiveness was reversed by injection of the nonspecific opioid antagonist naloxone. The effect of milk on fetal responsiveness to cutaneous stimulation was reversed by the kappa opioid antagonist nor-binaltorphimine, but not by the mu antagonist beta-funaltrexamine. Milk engages the endogenous opioid system of the fetal rat and affects fetal responsiveness by interacting with the kappa receptors of the opioid system.

Aging↗
PubMed1992

Opioid control of the fetal stretch response: implications for the first suckling episode.

Upon their first experience with milk, fetal rats express a stretch response that is similar to the postnatal behavior exhibited by infant rats at the nipple. Fetuses also possess a functional opioid system that is activated by prenatal milk exposure. The opioid receptor antagonist naloxone and the specific kappa antagonist nor-binaltorphimine blocked the stretch response and prevented the increase in rearlimb activity that is typically induced by milk. The mu antagonist beta-funaltrexamine blocked the stretch while permitting the expression of rearlimb activity. The kappa agonist U50,488 promoted rearlimb activity in the absence of milk, whereas the mu agonist [D-Ala2,NMe-Phe4,Gly5-ol]-enkephalin (DAMGO) exerted little influence on fetal behavior. Fetuses pretreated with U50,488 stretched to nonmilk stimuli (saline or lemon), but fetuses pretreated with DAMGO did not. Opioid activation is part of a chain of events that culminates in the fetal stretch response and may be important in promoting milk ingestion during the newborn's first suckling episode.

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PubMed1992

Habituation in the rat fetus.

Rat fetuses exhibit motor and cardiac responses to chemosensory stimulation on Days 20 and 21 of gestation. The first experiment demonstrated that fetuses exhibit an increase in overall motor activity and decrease in heartrate in response to an initial intraoral infusion of a lemon solution. After a series of nine exposures, however, fetuses no longer exhibit motor or cardiac responses to lemon infusion, suggesting the existence of a habituation-like process. Responsiveness recovers spontaneously following a 3- to 9-min period without stimulation. In a second experiment, a dishabituation treatment was administered to distinguish habituation, which is a centrally mediated decrement in response, from effector fatigue, sensory adaptation, and other peripheral mechanisms that can result in reduced responsiveness. A single infusion of mint following a series of nine lemon exposures was effective in reinstating fetal motor responses to lemon on both Days 20 and 21, but reinstated cardiac responses only on Day 21. Rat fetuses habituate to repeated chemosensory stimulation, suggesting the utility of the habituation paradigm in measuring CNS development during the perinatal period.

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PubMed1991

Thy-1 antigen is specific to ganglion cells in chicks.

The cellular localization of Thy-1 in the chick retina was investigated by selectively destroying certain populations of neurons with toxins. In control retinae four weeks after intravitreal injection of vehicle, there was strong immunoreactivity for Thy-1 in the nerve fibre layer, ganglion cell layer and inner plexiform layer. By contrast, 4 weeks after intraocular injection with 1.25 nmol of colchicine, virtually all ganglion cells had been destroyed, but most amacrine cells remained. Very little Thy-1 immunoreactivity was evident in these retinae. Four weeks after intraocular injection of 2 mumol of N-methyl-D-aspartic acid (NMDA), a large proportion of amacrine cells had been destroyed, but most ganglion cells remained. In these retinae Thy-1 immunoreactivity was present in the nerve fibre, ganglion cell and inner plexiform layers, in the latter with greater intensity than in controls. We conclude that in chicks the Thy-1 antigen is principally, if not exclusively restricted to ganglion cells.

Animals↗
PubMed1991

The amniotic sac as scaffolding: prenatal ontogeny of an action pattern.

Intraoral lemon infusion elicits facial wiping behavior in fetal rats on Days 20 and 21 of gestation. On Day 19, fetuses tested in a warm saline bath respond to infusion but do not express the wiping response. In contrast, fetuses tested within the amniotic sac exhibit wiping. Fetal movements after infusion were analyzed on Days 19 and 20 in both the bath and amnion environments. Facial wiping is assembled from simpler components in both real time (during the 15 s after infusion) and developmental time (over Days 19-20 of gestation). In real time, the wiping response occurs following a brief period of fetal activity comprising head and forelimb movements. After the wiping bout is initiated, strokes by left and right forelimbs increase in duration and become synchronized. In developmental time, components of the wiping response (forelimb strokes) are consistently expressed on Day 19, but other components (head stabilization) are lacking when fetuses are tested in bath. The amniotic sac appears to provide scaffolding that reduces head movement and promotes paw-face contact, thus facilitating facial wiping.

Amnion↗
PubMed1991

Heart rate response of the rat fetus and neonate to a chemosensory stimulus.

Resting heart rate (HR) and HR responses of fetal and neonatal rats are described before and after intraoral infusion of isotonic saline or lemon solution. Stable measurements of resting HR were obtained for fetuses over the last three days of gestation (E19, E20, E21) and pups on the day of birth (P0) and four subsequent postnatal ages (P1, P3, P5, P7). Resting HR decreased significantly on P0 relative to the three prenatal ages and exhibited a linear increase thereafter. Variability in resting HR was pronounced on E21, decreased sharply after birth, and gradually increased through P7. Developmental changes in the HR response of fetuses and pups were evident following infusion of lemon. Fetal HR responses to lemon were characterized by bradycardia, which increased in magnitude through P1, diminished after P1, and eventually changed to tachycardia by P7. Both resting HR and HR responses to chemosensory stimulation point to the immediate perinatal period as a time of quantitative and qualitative change during sensory development.

Aging↗
PubMed1991

Conditioned activation of fetal behavior.

Previous demonstrations of prenatal learning have relied upon experimental protocols involving training at one gestational age and testing at a later age, potentially confounding effects of experience and retention with developmental changes in the fetus's behavioral repertoire. In this study, a single-session paradigm, which involved the pairing of a neutral chemosensory stimulus (sucrose CS) with a second stimulus that activates behavior (lemon US), was used to assess the learning capacity of the rat fetus. Four CS-US pairings were effective in promoting behavioral activity in 20-day-old rat fetuses when they were reexposed to the sucrose CS alone. The functional expression of conditioned behavioral activation on day 20 of gestation occurs at a time when CNS structures, many of which are involved in sensory processing and learning in older animals, are still undergoing rapid differentiation in the rat fetus.

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PubMed1990

Olfactory bulb transection alters fetal behavior after chemosensory but not tactile stimulation.

Rat fetuses respond to an intraoral infusion of lemon extract with an increase in overall activity and facial-wiping behavior. Other studies have suggested a role for olfaction in mediating fetal responses to chemosensory stimuli. In the present study, a micro-knife was used to surgically isolate the main and accessory olfactory bulbs from more caudal structures in the fetal brain. Fetuses that received this transection procedure or a sham treatment showed normal levels of non-evoked motor activity during the period prior to chemosensory infusion. Surgical isolation of the olfactory bulbs had no effect on fetal response to perioral tactile stimulation. Behavioral responses to infusion were diminished but not eliminated in fetuses with olfactory bulb transections. The olfactory bulb, which is functional in spite of its anatomical immaturity, plays a role in the control of fetal behavior.

Animals↗
PubMed1990

Müller cells in adult rabbit retinae: morphology, distribution and implications for function and development.

We describe the morphology and distribution of Müller cells in wholemounts of rabbit retinae labelled with either monoclonal antibodies (anti-Vimentin, 3H3, 4D6, and 4H11), or intracellular horseradish peroxidase. Several new features of Müller cell organization are noted. First, Müller cells appear to compose a single morphological class and their morphology varies systematically with retinal thickness. Second, in contrast to other retinal glia, Müller cells have a neuronlike distribution, with a peak density of 10,700-15,000 cells per mm2 at the visual streak and a minimum density of 4,400-6,000 per mm2 at both the superior and inferior retinal edges. There are 4.2 +/- 0.5 x 10(6) Müller cells per retina. Third, unlike in other species, rabbit Müller cells do not contact blood vessels, suggesting that they do not participate in the transfer of metabolites or in the blood:retinal barrier. Fourth, each Müller cell has a vitread endfoot about 20-40 microns in diameter composed of numerous fimbriae. The fimbriae from a single Müller cell generally contact several axon fascicles in the nerve fibre layer, and at each point along its length each fascicle is enclosed by the overlapping fimbriae from several Müller cells. Fifth, in the inner and outer plexiform layers, numerous filamentous branchlets extend 20 microns or more from the radial trunk, interweaving with branchlets from nearby Müller cells to form dense and continuous strata. In the ganglion cell layer and outer nuclear layer, Müller cell processes completely wrap neuronal somata, whereas in the inner nuclear layer they partially wrap somata. We discuss the functional and developmental implications of these observations.

Animals↗
PubMed1990

Rat fetuses respond to chemical stimuli in gas phase.

Fetuses exhibit behavioral responses to intraoral infusions of chemical solutions presented in liquid phase, including an increase in overall activity and the production of a species-typical action pattern, facial wiping. A series of experiments were conducted in which chemical compounds with strong olfactory characteristics--citral and cyclohexanone--were presented in gas phase to rat fetuses on day 20 of gestation. Fetuses exhibited similar behavioral responses to stimuli presented in liquid and gas phases, suggesting a common basis for the processing of prenatal chemosensory information. Chemosensory stimuli in gas phase are sufficient to elicit both behavioral activation and a stereotypic action pattern of the rat fetus, patterns that anticipate postnatal olfactory-directed behavior. These results suggest that prenatal chemosensory experience, which normally occurs in an aqueous medium, may be relevant to the development of postnatal behavior that is directed by airborne olfactory cues.

Animals↗
PubMed1990

The visual pathways of eutherian mammals and marsupials develop according to a common timetable.

Data from cats, ferrets, hamsters, macaques, mice, rabbits and rats concerning the time of occurrence of 26 developmental events involved in the establishment of the retinofugal, geniculocortical, corticogeniculate and corticocollicular pathways were analysed. For each species the timing of developmental events was expressed as a proportion of the period between conception and eye opening ('caecal period'). For 6 of these events, the values for all species fell within a range of 1-5% of the caecal period, the values for 11 other events fell within a range of 6-10% of the caecal period, 4 events had ranges of 11-15% of the caecal period, and only 5 events were spread over more than 15% of the caecal period. The 26 events had an overall mean variation of about 11% of the caecal period, suggesting that the visual pathways of eutherian mammals develop according to a common 'timetable' that is related to the duration of the caecal period. One of the roles of this common timetable may be to assist the establishment of orderly interconnections between the visual centres. Relatively few data are available concerning the timing of developmental events in marsupial visual pathways. However, it is apparent that, during the first half of the caecal period, most events occur much earlier in marsupials than in eutherians, whereas during the second half of the caecal period most events occur at the same stages of the caecal period in both marsupials and eutherians. The accelerated rate of visual development during the first half of the caecal period in marsupials may be related to the precocious development that they undergo prior to their very early birth.

Animals↗
PubMed1989

Evidence for three morphological classes of astrocyte in the adult rabbit retina: functional and developmental implications.

Commercially available antibodies to glial fibrillary acidic protein (GFAP) and vimentin were used in conjunction with our own antibodies (3F11, MA1 and 4D6) to label astrocytes in the adult albino rabbit retina. Anti-GFAP labels the entire astrocyte population and shows them to be morphologically diverse. By contrast, the remaining four antibodies label different subpopulations of astrocytes. Comparisons of the shapes and distributions of cells composing these subpopulations led us to distinguish three morphological classes: Class A are predominantly perivascular astrocytes, Class B are territorial and rarely contact vessels or axons, Class C (which seems to contain four subclasses) are astrocytes that are predominantly associated with axons.

Animals↗
PubMed1989

Somatostatinergic neurones of the developing human and cat retinae.

We have examined somatostatin-immunoreactive (S-IR) neurones in developing retinae of the human and cat. At 14 and 16 weeks' gestation (G14 and G16) in the human, S-IR cells were only found close to the putative fovea centralis, but by 18 weeks' gestation (G18), they were located in all retinal regions. By adulthood, the majority of S-IR cells were restricted to inferior retina. In the developing cat retina, two classes of S-IR cells were recognized. S1-IR cells were similar in morphology and distribution to adult cells: they had small round somata which were only found in inferior retina and gave rise to beaded processes which traversed the inner plexiform layer (IPL) and nerve fibre layer (NFL). S2-IR cells had larger somata located in the ganglion cell layer (GCL) and the label was compartmentalized within their cytoplasm. Most S2-IR cells had lost immunoreactivity by P (postnatal day) 25 and may have been alpha-ganglion cells transiently expressing somatostatin in association with their retention of plasticity into postnatal life.

Animals↗
PubMed1989

Nonuniform retinal expansion during the formation of the rabbit's visual streak: implications for the ontogeny of mammalian retinal topography.

We have studied the distribution of retinal ganglion cells (RGCs) which have been retrogradely labeled from massive bilateral injections of the enzyme horseradish peroxidase into the retino-recipient nuclei of foetal and postnatal albino rabbits aged from the 24th postconceptional day (24PCD) to adulthood. The number of labeled RGCs increases from about 447,000 on the 24PCD to a peak of about 525,000 on the 27PCD. From the 29PCD to birth (31/32PCD), the number of RGCs rapidly declines to about 375,000. During the next 20 d, the number of RGCs stabilizes at about 335,000. After the 51PCD, the number of RGCs gradually declines to the adult value of about 280,000. Retinal area steadily increases from about 40 mm2 on the 24PCD to about 500 mm2 in the adult, while RGC density decreases. However, the reduction in RGC density is nonuniform: RGC density in the visual streak drops from 18,600 RGCs mm2 on the 24PCD to 4700 RGCs/mm2 in the adult, whereas RGC densities at the superior and inferior edges of the retina decreases proportionally much more (from 9300 to 105 RGCs/mm2 and from 12,000 to 170 RGCs/mm2, respectively). As a result of this differential reduction in RGC density, the streak/inferior edge ratio changes from 1.6:1 to about 28:1. In the periods from the 24PCD to the 29PCD and from the 32PCD to adulthood, the proportional increases in the streak/superior edge and streak/inferior edge RGC density ratios are linearly related to the proportional increases in retinal area. However, between the 29PCD and 32PCD, the RGC density ratios increase at a greater rate than retinal area. We conclude that (1) the centro-peripheral difference in RGC density that is already present on the 24PCD might be attributable to differential RGC generation; (2) the redistribution of RGCs between the 24PCD and adulthood is mainly due to nonuniform expansion of the retina, with minimal expansion of the visual streak and maximal expansion at the superior and inferior retinal edges; and (3) a small component of the increase in the centro-peripheral RGC density ratio, which becomes apparent between the 29PCD and 32PCD, is probably due to differential RGC loss. We discuss the pattern of retinal expansion in the rabbit and the factors which might contribute to it.

Animals↗
PubMed1989

Cryptopsychobiology: the appearance, disappearance, and reappearance of a species-typical action pattern during early development.

Late in gestation, intraoral infusion of lemon elicits a facial wiping response from rat fetuses. This facial wiping response is isomorphic with that of older pups and adult rats exposed to aversive oral stimulation. Most studies of the postnatal development of aversive responses have demonstrated that facial wiping does not appear in the repertoire of rat pups until the second postnatal week. In certain test situations, however, wiping can be elicited from neonatal rats. This fact suggests that the expression of facial wiping by neonates is constrained or facilitated by the environmental conditions present at the time of testing. In this report, a series of seven experiments is described that document the wiping response of rat fetuses and pups in age-typical environments, and an environmental constraint hypothesis is examined. Examination of the ontogeny of facial wiping in this manner highlights issues that should be addressed in studies of behavioral continuity between the prenatal and the postnatal periods.

Aging↗