Recent findings in chronically instrumented animals challenge the classic concept that baroreflexes do not play a role in the chronic regulation of arterial pressure. As alterations in renal excretory function are of paramount importance in the chronic regulation of arterial pressure, several of these recent studies have focused on the long-term interactions between the baroreflex and the kidneys during chronic perturbations in arterial pressure and body fluid volumes. An emerging body of evidence indicates that the baroreflex is chronically activated in several experimental models of hypertension, but in most cases, the duration of these studies has not exceeded 2 wk. Although these studies suggest that the baroreflex may play a compensatory role in attenuating the severity of the hypertension, possibly even in primary hypertension with uncertain causes of sympathetic activation, there has been only limited assessment of the quantitative importance of this interaction in the regulation of arterial pressure. In experimental models of secondary hypertension, baroreflex suppression of renal sympathetic nerve activity is sustained and chronically promotes sodium excretion. This raises the possibility that the renal nerves may be the critical efferent link for baroreceptor-induced suppression of central sympathetic output through which long-term compensatory reductions in arterial pressure are produced. This contention is supported by strong theoretical evidence but must be corroborated by experimental studies. Finally, although it is now clear that pressure-induced increases in baroreflex activity persist for longer periods of time than previously suggested, studies using new tools and novel approaches and extending beyond 2 wk of hypertension are needed to elucidate the true role of the baroreflex in the pathogenesis of clinical hypertension.

We investigated associations between children's representations of mothers in their play narrative and measures of children's and mothers' socioemotional adaptation, and explored the development of these representations between the ages of 4 and 5 years. Fifty-one children were interviewed using the MacArthur Story-Stem Battery to obtain their narrative representations of mothers. Positive, Negative, and Disciplinary representation composites were generated. Children who had more Positive and Disciplinary representations and fewer Negative representations had fewer behavior problems and their mothers reported less psychological distress. In addition, 5-year-olds had more Positive and Disciplinary representations and fewer Negative representations than did 4-year-olds, and there was moderate stability in individual differences in children's representations of mothers across the 2 ages. The results add an important dimension to research on parent-child relationships--that of children's perspectives on these relationships.

Abstract-Recent studies indicate that renal sympathetic nerve activity is chronically suppressed in angiotensin (Ang II) hypertension and that baroreflexes play a critical role in mediating this response. To support these findings, we determined whether the hypertension associated with chronic infusion of Ang II at 4.8 pmol/kg per minute (5ng/kg per minute) produces sustained activation of medullary neurons that participate in the central baroreceptor reflex pathway. We used Fos-like (Fos-Li) protein immunohistochemical methods to determine activation of neurons in the nucleus tractus solitarius (NTS), caudal ventrolateral medulla (CVLM), and rostral ventrolateral medulla (RVLM). Results were compared in three groups of chronically instrumented dogs subjected to infusion of: 1) saline (control); 2) Ang II-2 hours (acute); and 3) Ang II-5 days (chronic here has been a long-standing interest in the mechanisms that contribute to the hypertension induced by pathophysiological levels of angiotensin (Ang II) in the circulation. Although circulating Ang II has sustained actions on the kidneys, vasculature, and adrenal glands that promote chronic hypertension, acute studies have also demonstrated that circulating Ang II can act in the central nervous system to increase sympathetic activity and arterial pressure. 1 However, the relevance of these acute studies to the pathophysiological role of Ang II in hypertension has not been settled. In large part, this is because of technical limitations that prevent determination of both the long-term changes in sympathetic activity and the sustained influence of the sympathetic nervous system on renal excretory function.It is well established that the kidneys play a critical role in the long-term regulation of arterial pressure. 2 The few studies that have determined the temporal changes in renal sympathetic nerve activity and the resultant neurally-induced renal excretory responses during chronic Ang II infusion strongly indicate interactions between the renin-angiotensin and sympathetic nervous systems in the genesis of the hypertension. [3][4][5][6][7] In direct opposition to the notion that the sympathetic nervous system contributes to Ang II hypertension, these studies indicate that suppression of renal sympathetic nerve activity and attendant increases in sodium excretion are sustained responses in Ang II hypertension. 3-7 These findings therefore suggest that the sympathetic nervous system actually attenuates rather than contributes to the severity of Ang II hypertension. Furthermore, based on a recent study in chronically instrumented dogs, it seems that chronic renal sympathoinhibition in Ang II hypertension is mediated by baroreflexes. 6 As it is well established that baroreceptors undergo rapid adaptation and resetting, 8 this recent study is rather surprising. In fact, the implication of this study is that the baroreflex does not completely reset in chronic hypertension and, therefore, may play a role in the chronic regulation of arterial pressure. The primary object...

The superior colliculus (SC), which directs orienting movements of both the eyes and head, is reciprocally connected to the mesencephalic reticular formation (MRF), suggesting the latter is involved in gaze control. The MRF has been provisionally subdivided to include a rostral portion, which subserves vertical gaze, and a caudal portion, which subserves horizontal gaze. Both regions contain cells projecting downstream that may provide a conduit for tectal signals targeting the gaze control centers which direct head movements. We determined the distribution of cells targeting the cervical spinal cord and rostral medullary reticular formation (MdRF), and investigated whether these MRF neurons receive input from the SC by the use of dual tracer techniques in Macaca fascicularis monkeys. Either biotinylated dextran amine or Phaseolus vulgaris leucoagglutinin was injected into the SC. Wheat germ agglutinin conjugated horseradish peroxidase was placed into the ipsilateral cervical spinal cord or medial MdRF to retrogradely label MRF neurons. A small number of medially located cells in the rostral and caudal MRF were labeled following spinal cord injections, and greater numbers were labeled in the same region following MdRF injections. In both cases, anterogradely labeled tectoreticular terminals were observed in close association with retrogradely labeled neurons. These close associations between tectoreticular terminals and neurons with descending projections suggest the presence of a trans-MRF pathway that provides a conduit for

Omnipause neurons (OPNs) within the nucleus raphe interpositus (RIP) help gate the transition between fixation and saccadic eye movements by monosynaptically suppressing activity in premotor burst neurons during fixation, and releasing them during saccades. Premotor neuron activity is initiated by excitatory input from the superior colliculus (SC), but how the tectum's saccade-related activity turns off OPNs is not known. Since the central mesencephalic reticular formation (cMRF) is a major SC target, we explored whether this nucleus has the appropriate connections to support tectal gating of OPN activity. In dual-tracer experiments undertaken in macaque monkeys (Macaca fascicularis), cMRF neurons labeled retrogradely from injections into RIP had numerous anterogradely labeled terminals closely associated with them following SC injections. This suggested the presence of an SC-cMRF-RIP pathway. Furthermore, anterograde tracers injected into the cMRF of other macaques labeled axonal terminals in RIP, confirming this cMRF projection. To determine whether the cMRF projections gate OPN activity, postembedding electron microscopic immunochemistry was performed on anterogradely labeled cMRF terminals with antibody to GABA or glycine. Of the terminals analyzed, 51.4% were GABA positive, 35.5% were GABA negative, and most contacted glycinergic cells. In summary, a trans-cMRF pathway connecting the SC to the RIP is present. This pathway contains inhibitory elements that could help gate omnipause activity and allow other tectal drives to induce the bursts of firing in premotor neurons that are necessary for saccades. The non-GABAergic cMRF terminals may derive from fixation units in the cMRF.

A gaze-related region in the caudal midbrain tegementum, termed the central mesencephalic reticular formation (cMRF), has been designated on electrophysiological grounds in monkeys. In macaques, the cMRF correlates with an area in which reticulotectal neurons overlap with tectoreticular terminals. We examined whether a region with the same anatomical characteristics exists in cats by injecting biotinylated dextran amine into their superior colliculi. These injections showed that a cat cMRF is present. Not only do labeled tectoreticular axons overlap the distribution of labeled reticulotectal neurons, these elements also show numerous close boutonal associations, suggestive of synaptic contact. Thus, the presence of a cMRF that supplies gaze-related feedback to the superior colliculus may be a common vertebrate feature. We then investigated whether cMRF connections indicate a role in the head movement component of gaze changes. Cervical spinal cord injections in both the cat and monkey retrogradely labeled neurons in the ipsilateral, medial cMRF. In addition, they provided evidence for a spinoreticular projection that terminates in this same portion of the cMRF, and in some cases contributes boutons that are closely associated with reticulospinal neurons. Injection of the physiologically defined, macaque cMRF demonstrated that this spinoreticular projection originates in the cervical ventral horn, indicating it may provide the cMRF with an efference copy signal. Thus, the cat and monkey cMRFs have a subregion that is reciprocally connected with the ipsilateral spinal cord. This pattern suggests the Abbreviations used: BC 5 brachium conjunctivum; cMRF 5 central mesencephalic reticular formation; Cun 5 cuneiform nucleus; C1 5 first segment of the cervical spinal cord; C2 5 second segment of the cervical spinal cord; C3 5 third segment of the cervical spinal cord; DF 5 dorsal funiculus; DH 5 dorsal horn; DR 5 dorsal raphe; EWu 5 urocortin containing; Edinger Westphal nucleus; IC 5 inferior colliculus; InC 5 interstitial nucleus of Cajal; LF 5 lateral funiculus; MG 5 medial geniculate nucleus; MRF 5 midbrain reticular formation; nB 5 nucleus of the brachium of the inferior colliculus; nPC 5 nucleus of the posterior commissure; PAG 5 periaqueductal gray; piMRF 5 peri InC mesencephalic reticular formation; PRF 5 pontine reticular formation; Pt 5 pretectum; SN 5 substantia nigra; R 5 red nucleus; SC 5 superior colliculus; SGI 5 intermediate gray layer; SGP 5 deep gray layer; SOA 5 supraoculomotor area; Vc 5 spinal trigeminal nucleus pars caudalis; VF 5 ventral funiculus; VH 5 ventral horn; 3 5 oculomotor nucleus; 4 5 trochlear nucleus.

PurposeThese experiments were designed to reveal the location of the premotor neurons that have previously been designated physiologically as the midbrain near response cells controlling vergence, lens accommodation, and pupillary constriction in response to target distance.MethodsTo identify this population, the fixed N2c strain of rabies virus was injected into the ciliary body of seven Macaca fascicularis monkeys. The virus was trans-synaptically transported to the brain. Following a 58- to 76-hour survival, animals were perfused with formalin fixative. After frozen sectioning, tissue was reacted to reveal the location of the infected populations by use of a monoclonal anti-rabies antibody. Another series of sections was processed to determine which of the rabies-positive cells were cholinergic motoneurons by use of an antibody to choline acetyl transferase.ResultsAt earlier time points, only cholinergic cells in the preganglionic Edinger-Westphal nucleus ipsilateral to the injection were labeled. At later time points, an additional population of noncholinergic, premotor cells was present. These were most numerous at the caudal end of the supraoculomotor area, where they formed a bilateral band, oriented mediolaterally immediately above the oculomotor nucleus. Rostral to this, a smaller bilateral population was located near the midline within the supraoculomotor area.ConclusionsMost lens preganglionic motoneurons are multipolar cells making up a continuous column within the Edinger-Westphal nucleus. A population of premotor cells that likely represents the midbrain near response cells is located in the supraoculomotor area. These cells are bilaterally distributed relative to the eye they control, and are most numerous caudally.

The central mesencephalic reticular formation is physiologically implicated in oculomotor function and anatomically interwoven with many parts of the oculomotor system’s premotor circuitry. This study in Macaca fascicularis monkeys investigates the pattern of central mesencephalic reticular formation projections to the area in and around the extraocular motor nuclei, with special emphasis on the supraoculomotor area. It also examines the location of the cells responsible for this projection. Injections of biotinylated dextran amine were stereotaxically placed within the central mesencephalic reticular formation to anterogradely label axons and terminals. These revealed bilateral terminal fields in the supraoculomotor area. In addition, dense terminations were found in both the preganglionic Edinger-Westphal nuclei. The dense terminations just dorsal to the oculomotor nucleus overlap with the location of the C-group medial rectus motoneurons projecting to multiply innervated muscle fibers suggesting they may be targeted. Minor terminal fields were observed bilaterally within the borders of the oculomotor and abducens nuclei. Injections including the supraoculomotor area and oculomotor nucleus retrogradely labeled a tight band of neurons crossing the central third of the central mesencephalic reticular formation at all rostrocaudal levels, indicating a subregion of the nucleus provides this projection. Thus, these experiments reveal that a subregion of the central mesencephalic reticular formation may directly project to motoneurons in the oculomotor and abducens nuclei, as well as to preganglionic neurons controlling the tone of intraocular muscles. This pattern of projections suggests an as yet undetermined role in regulating the near triad.