Client-centered therapy: where has it been and where is it going? A comment on Hathaway (1948)

We review the article by Hathaway (1948) critiquing nondirective therapy. We summarize Hathaway's concerns about nondirective therapy and psychotherapy research in general and consider the historical context of the article. Then we discuss progress on methodological concerns raised by Hathaway, empirical evidence obtained in the last 50 years about the efficacy of client-centered therapy and other kinds of psychotherapy, the current status of client-centered therapy, and projections for the future.

MHC class II pseudogene and genomic signature of a 32-kb cosmid in the house finch (Carpodacus mexicanus)

Large-scale sequencing studies in vertebrates have thus far focused primarily on the genomes of a few model organisms. Birds are of interest to genomics because of their much smaller and highly streamlined genomes compared to mammals. However, large-scale genetic work has been confined almost exclusively to the chicken; we know little about general aspects of genomes in nongame birds. This study examines the organization of a genomic region containing an Mhc class II B gene in a representative of another important lineage of the avian tree, the songbirds (Passeriformes). We used a shotgun sequencing approach to determine the sequence of a 32-kb cosmid insert containing a strongly hybridizing Mhc fragment from house finches (Carpodacus mexicanus). There were a total of three genes found on the cosmid clone, about the gene density expected for the mammalian Mhc: a class II Mhc beta-chain gene (Came-DAB1), a serine-threonine kinase, and a zinc finger motif. Frameshift mutations in both the second and third exons of Came-DAB1 and the unalignability of the gene after the third exon suggest that it is a nonfunctional pseudogene. In addition, the identifiable introns of Came-DAB1 are more than twice as large as those of chickens. Nucleotide diversity in the peptide-binding region of Came-DAB1 (Pi = 0.03) was much lower than polymorphic chicken and other functional Mhc genes but higher than the expected diversity for a neutral locus in birds, perhaps because of hitchhiking on a selected Mhc locus close by. The serine-threonine kinase gene is likely functional, whereas the zinc finger motif is likely nonfunctional. A paucity of long simple-sequence repeats and retroelements is consistent with emerging rules of chicken genomics, and a pictorial analysis of the "genomic signature" of this sequence, the first of its kind for birds, bears strong similarity to mammalian signatures, suggesting common higher-order structures in these homeothermic genomes. The house finch sequence is among a very few of its kind from nonmodel vertebrates and provides insight into the evolution of the avian Mhc and of avian genomes generally.

Incidence of myoendothelial gap junctions in the proximal and distal mesenteric arteries of the rat is suggestive of a role in endothelium-derived hyperpolarizing factor-mediated responses

Although the chemical nature of endothelium-derived hyperpolarizing factor (EDHF) remains elusive, electrophysiological evidence exists for electrical communication between smooth muscle cells and endothelial cells suggesting that electrotonic propagation of hyperpolarization may explain the failure to identify a single chemical factor as EDHF. Anatomical evidence for myoendothelial gap junctions, or the sites of electrical coupling, is, however, rare. In the present study, serial-section electron microscopy and reconstruction techniques have been used to examine the incidence of myoendothelial gap junctions in the proximal and distal mesenteric arteries of the rat where EDHF responses have been reported to vary. Myoendothelial gap junctions were found to be very small in the mesenteric arteries, the majority being <100 nm in diameter. In addition, they were significantly more common in the distal compared with the proximal regions of this arterial bed. Pentalaminar gap junctions between adjacent endothelial cells were much larger and were common in both proximal and distal mesenteric arteries. These latter junctions were frequently found near the myoendothelial gap junctions. These results provide the first evidence for the presence of sites for electrical communication between endothelial cells and smooth muscle cells in the mesenteric vascular bed. Furthermore, the relative incidence of these sites suggests that there may be a relationship between the activity of EDHF and the presence of myoendothelial gap junctions.

Song-type matching between neighbouring song sparrows

In our study population, neighbouring song sparrows typically share two or more of their 6-10 song types. In an earlier experiment, we found that established neighbours typically reply to playback of neighbour-shared song with a different song they share with that neighbour ('repertoire matching'), rather than with the same song ('type matching') or with a nonshared song. In the present experiment, we considered the hypothesis that type matching is a threat or warning signal (Krebs et al. 1981, Animal Behaviour, 29, 918-923). We tested the specific prediction that a bird is more likely to type-match early in the breeding season when territory boundaries are new and still unstable, and more likely to repertoire-match later in the season, once those boundaries have become well established. Birds were played a shared song of a new neighbour once early (April) and again late (June) in the breeding season. As predicted, early in the season birds usually type-matched the playback (73% of the trials) but late in the season they type-matched only rarely (18%); birds never replied (early or late) with a nonshared song type. Copyright 2000 The Association for the Study of Animal Behaviour.

Mechanisms underlying spontaneous rhythmical contractions in irideal arterioles of the rat

1. Mechanisms underlying spontaneous rhythmical contractions have been studied in irideal arterioles of the rat using video microscopy and electrophysiology. 2. Rhythmical contractions (4 min-1) were more common during the second and third postnatal weeks and were always preceded by large, slow depolarizations (5-40 mV). 3. Spontaneous contractions were unaffected by tetrodotoxin (1 microM), neurotransmitter receptor antagonists, the sympathetic neurone blocker, guanethidine (5 microM) or sensory neurotoxin, capsaicin (1 microM). 4. Stimulation of sensory nerves inhibited spontaneous activity and this was not prevented by L-NAME (10 microm). 5. L-NAME (10 microm) caused an increase in frequency of spontaneous contractions, while forskolin (30 nM), in the presence of L-NAME, abolished spontaneous, but not nerve-mediated, contractions. 6. Spontaneous activity was not affected by felodipine (1 nM) or nifedipine (1 microM), but was abolished by cadmium chloride (1 microM) or superfusion with calcium-free solution. 7. Caffeine (1 mM), thapsigargin (2 microM) and cyclopiazonic acid (3 microM), but not ryanodine (3 microM), abolished spontaneous and nerve-mediated contractions. After preincubation in L-NAME (10 microM), cyclopiazonic acid abolished spontaneous contractions only. 8. Spontaneous depolarizations and contractions were abolished by 18alpha-glycyrrhetinic acid (20 microM). 9. Results suggest that spontaneous rhythmical contractions are myogenic and result from the cyclical release of calcium from intracellular stores, without a contribution from voltage-dependent calcium channels. Intercellular coupling through gap junctions appears to be essential for co-ordination of these events which could be modulated by nitric oxide and increases in cAMP. The possibility that different intracellular stores underly spontaneous and nerve-mediated contractions is discussed.

Lessons learned from ACGME

BACKGROUND AND OBJECTIVES

The year 1998 brought to a close our 6 years of service as representatives to the Accreditation Council for Graduate Medical Education. These have been challenging times for graduate medical education (GME), and our time on the council has been an educational experience of the first order. This paper describes our experiences and summarizes the issues we believe lie ahead for GME, particularly for family practice residency programs.

Physiological and anatomical studies of the development of the sympathetic innervation to rat iris arterioles

The development of the sympathetic innervation to rat irideal arterioles has been investigated using histochemical and in vitro pharmacological and electrophysiological methods. A plexus of fibres and varicosities appeared over the surface of the vessels after the first postnatal week and increased to reach a maximum density during the fourth postnatal week. Transmural nerve stimulation produced small, consistent contractions that were first recorded in arterioles of 7-day old rats. Contractions became larger and faster, reaching the adult form during the fourth postnatal week. Contractions became more sensitive to the alpha1-adrenoceptor antagonists, prazosin and naftopidil, and less sensitive to the alpha1A/D antagonist, WB4101 and alpha2 antagonist, yohimbine, during development. At both 10 and 21 days, contractile responses resulted from the release of intracellular calcium as they were abolished by caffeine (10(-3) M), thapsigargin (2 x 10(-6) M) and cyclopiazonic acid (3 x 10(-6) M), but not by nifedipine (10(-6) M). Intracellular recordings showed that nerve stimulation produced large, slow depolarizations at all ages tested. Time to peak potential decreased during development, while the amplitude of the depolarizations did not vary significantly. Results suggest that, throughout development, sympathetic nerves cause constriction of iris arterioles due to the release of noradrenaline and activation of alpha-adrenoceptors on the smooth muscle cells. Early responses involved both alpha1- and alpha2-adrenoceptors, while later responses were due to alpha1-adrenoceptors only. Irrespective of these changes in adrenoceptor subtypes, smooth muscle contraction resulted from the mobilization of intracellular calcium suggesting that both alpha1- and alpha2-adrenoceptors were coupled to pathways which accessed this source of calcium.

Specialised sympathetic neuroeffector associations in immature rat iris arterioles

Sympathetic nerve-mediated vasoconstriction in iris arterioles of mature rats occurs via the activation of alpha(1B)-adrenoceptors alone, while in immature rat iris arterioles, vasoconstriction occurs via activation of both alpha1- and alpha2-adrenoceptors. In mature rats the vast majority of sympathetic varicosities form close neuroeffector junctions. Serial section electron microscopy of 14 d iris arterioles has been used to determine whether restriction in physiological receptor types with age may result from the establishment of these close neuroeffector junctions. Ninety varicosities which lay within 4 microm of arteriolar smooth muscle were followed for their entire length. Varicosities rarely contained dense cored vesicles even after treatment with 5-hydroxydopamine. 47 % of varicosities formed close associations with muscle cells and 88 % formed close associations with muscle cells or melanocytes. Varicosities in bundles were as likely as single varicosities to form close associations with vascular smooth muscle cells, although the distribution of synaptic vesicles in single varicosities did not show the asymmetric accumulation towards the smooth muscle cells seen in the varicosities in bundles which were frequently clustered together. We conclude that restriction of physiological receptor types during development does not appear to correlate with the establishment of close neuroeffector junctions, although changes in presynaptic structures may contribute to the refinement of postsynaptic responses.

Development of peripheral autonomic synapses: neurotransmitter receptors, neuroeffector associations and neural influences

1. The functional innervation of autonomic target tissues occurs early during development, at a time when both the nerves and post-synaptic target tissues are still differentiating. 2. Physiological responses appear soon after the arrival of the first fibres when uptake and release mechanisms within the nerves are already functional. Initial responses differ from those in the mature animal, both in the form and, frequently, in the subtypes of receptors involved. 3. Results of a number of studies suggest that the initial expression of neurotransmitter receptors during development is largely independent of neural influences. Changes recorded in neurotransmitter receptor expression during development appear to be similarly independent of neural influences. 4. While signal transduction pathways coupling adrenergic neurotransmitter receptors to effector responses appear to develop independently of the nerves, the efficient coupling of muscarinic receptors often requires the action of the neurotransmitter, acetylcholine. 5. During the period of synapse formation, the neural plexus continues to expand. While developing varicosities can release the neurotransmitter, the capacity for neurotransmitter retention appears to be restricted. Developmental changes in the neurotransmitters that produce functional responses, while well known in the sweat glands, may also be seen in more subtle forms in other target tissues. 6. Ultrastructural studies suggest that close physical associations between the membranes of the release sites of the developing nerves and the target cells may form early during development when physiological responses are still immature. These close associations could enable more specific reciprocal interactions between nerves and target cells involving known and novel growth factors, neuropeptides and cytokines important in shaping the mature synaptic characteristics.

Neuroreceptor mRNA expression in the rat mesenteric artery develops independently of innervation

Studies in autonomic targets have shown that nerves may be required for the development and maintenance of postsynaptic receptor populations. We have examined this relationship in the rat mesenteric artery, assessing mRNA expression levels for a range of neuroreceptors after neonatal sympathectomy, using 6-hydroxydopamine or antisera directed against nerve growth factor, and sensory denervation, using capsaicin. Total RNA was extracted from 28 day old rats and reverse transcription-polymerase chain reaction was performed, using primers specific for the alpha1(A,B,D)- and alpha2(A,B,C)-adrenergic, neurokinin (NKI-NK3), muscarinic (M1-M5) and P2X purinergic (P2x1-7) receptor families. Results showed no decreases in mRNA expression of any of the specific receptor subtypes after either sympathetic or sensory denervation. Small increases in mRNA expression were detected following sensory denervation for some of the receptor subtypes. We conclude that neither sympathetic nor sensory nerves are mandatory for the expression of mRNA of a range of neuroreceptors in the mesenteric vascular bed of the rat.

The anion transport inhibitor DIDS activates a Ba2+-sensitive K+ flux associated with hepatic exocrine secretion

4,4'-Diisothiocyanatostilbene-2,2'-disulfonate (DIDS), an anion transport inhibitor and choleretic organic anion, was used to study the relationship between putative DIDS-sensitive K channels and exocrine secretion in the isolated and bile duct cannulated perfused rat liver. Bile flow, DIDS excretion, and effluent perfusate K+ content were measured. DIDS (125 microM) caused a doubling in bile generation concomitant with its appearance in bile, confirming earlier reports. Furthermore, DIDS induced a transient increase in perfusate K+ concentration that peaked prior to the biliary parameters and, after 10 min, reversed to net uptake that fully compensated for the initial release. The K channel blocker Ba2+ (1 mM) strongly inhibited the release phase along with the accompanying choleresis and DIDS excretion. Ouabain (13.5 microM) alone was choleretic and hyperkalemic and, when applied in combination with DIDS, depressed DIDS excretion, choleresis, and DIDS-sensitive K+ uptake. To obtain further evidence for the presence of DIDS-sensitive K channels K+ flux was measured under the influence of different gradients of the cation. Perfusate K+ at 26 and 80 mM changed the DIDS-activated K+ flux from a transient outward to a sustained inward flux, and both DIDS excretion and bile flow decreased. Mean net K+ flux over 20 min DIDS perfusion changed from -1.3 +/-1.1 micromol/g with 5.9 mM K+ to -1304 +/- 55 micromol/g with 80 mM K+ in the perfusate. K+ efflux was fully and reversibly blocked by Ba2+ and influx was ouabain-insensitive, suggesting that the DIDS-activated K+ flux was channel mediated. The results show that a significant fraction of DIDS-induced bile generation is associated with K+ release that may be mediated by Ba(2+)-sensitive K channels, possibly of the inward rectifying type.

Cholestatic effects of the K+ channel blockers Ba2+ and TEA occur through different pathways in the rat liver

The role of K+ channels in bile acid-independent bile flow (BAIF) was studied in the isolated and bile duct-cannulated perfused rat liver by changing the driving force on K+ and by using a variety of K+ channel blockers. Bile flow rate, effluent perfusate K+ content, and portal pressure were measured. Increase in perfusate K+ from 5.9 to 80 mM caused inhibition of bile flow that could be fitted to a Boltzmann distribution, indicating partial dependence of bile formation on the K+ equilibrium potential and hence K+ channel activity. To investigate this further, the effects of compounds established as K+ channel blockers in liver or other tissues were surveyed. Ba2+ (1-5 mM) inhibited mean bile flow by 20%. Tetraethylammonium (TEA) inhibition of basal bile flow was biphasic with saturable (IC50 approximately 0.7 mM) and linear components. In contrast, infusion of the K+ channel blockers 4-aminopyridine (5 mM), cesium (2.5 mM), quinidine (0.1 mM), iberiotoxin (90 nM), or paxilline (100 nM) did not affect bile flow. As expected for a K+ channel blocker, Ba2+ caused a net K+ uptake. Conversely, TEA did not affect basal K+ fluxes, although TEA-induced cholestasis was accompanied by a 26% decrease in biliary glutathione excretion. These results suggest that the partial cholestasis induced by the K+ channel blockers Ba2+ and TEA occurs by significantly different mechanisms. Whereas the Ba2+ response implicates K+ channel activity as a significant driving force in BAIF, TEA-sensitive K+ channels are not present or are not involved in bile formation.

Immunohistochemical localisation of alpha1B-adrenergic receptors in the rat iris

Expression of the alpha1B-adrenergic receptor was investigated immunohistochemically in the rat iris, cornea and superior cervical ganglion by using antibodies raised in chickens immunised with a peptide corresponding to a portion of the 3rd intracellular loop common to the human, hamster and rat alpha1B-adrenergic receptor. Antibodies stained COS and HEK cell membranes of cells transfected with DNA encoding and expressing the hamster alpha1B-adrenergic receptor but not membranes from cells transfected with DNA encoding and expressing the rat alpha1A-adrenergic receptor or the rat alpha1D-adrenergic receptor. Staining was abolished by preincubation of the antibodies with the peptide used for immunisation. The distribution of alpha1B-adrenergic receptor was examined immunohistochemically with this antibody (1BI3) and a previously characterised antibody (Ab506) raised in rabbits against the carboxyl-terminal decapeptide of the receptor. In the iris, alpha1B-adrenergic receptor was detected in the dilator muscle, ciliary processes and posterior epithelium but no staining was observed in the superior cervical ganglion with either antibody. By contrast, differences in tissue staining between 1BI3 and Ab506 were observed for the sphincter muscle of the iris and for the cornea. 1BI3 stained both tissues intensely, whereas Ab506 only stained the cornea weakly and the sphincter not at all. Reverse transcription/polymerase chain reaction and nucleotide sequencing confirmed the presence of mRNA encoding the epitopes recognised by 1BI3 and Ab506 in cornea and other tissues. We conclude that (1) there is a good correlation between alpha1B-adrenergic receptor mRNA and protein expression in the iris, (2) mRNA, but not protein, is detected in the superior cervical ganglion and (3) additional processes may regulate receptor expression in the cornea.

Receptors involved in nerve-mediated vasoconstriction in small arteries of the rat hepatic mesentery

1. We have investigated the neurotransmitters and receptor subtypes involved in nerve-mediated vasoconstriction in small arteries of the rat hepatic mesentery. 2. A dense sympathetic innervation was demonstrated using catecholamine histochemistry and antibodies against the synaptic vesicle protein synaptophysin. 3. Reverse transcription-polymerase chain reaction (RT-PCR) demonstrated very strong expression of the alpha1A-adrenergic, neuropeptide Y (NPY) Y1, P2X1- and P2X4-purinergic receptors, moderate expression of the alpha2B-adrenergic receptor and the purinergic P2X5- and P2X7-receptors and weak expression of the alpha1B-, alpha1D-, alpha2A- and alpha2C-adrenergic receptors and the P2X2- and P2X3-purinergic receptors. NPY2 and P2X6 receptor expression was absent. 4. Electrical field stimulation (10 Hz, 10 s) produced contractions which were abolished by tetrodotoxin (10(-6) M) and/or guanethidine (GE, 5 x 10(-6) M) and a combination of benextramine (10(-5) M) and alpha,beta-methylene ATP, (alpha,beta-mATP, 3 x 10(-6) M) or PPADS (10(-5) M). Selective alpah1-adrenergic receptor antagonists showed the potency order of prazosin > WB-4101 > 5-methyl-urapidil > BMY 7378. Yohimbine (10(-8) M, 10(-7) M), alpha,beta-mATP (3 x 10(-6) M) and PPADS (10(-5) M) each enhanced the response to nerve stimulation. 5. Some experiments demonstrated a slow neurogenic contraction which was abolished by GE or the selective NPY1 receptor antagonist 1229U91 (6 x 10(-7) M). 6. We conclude that nerve-mediated vasoconstriction results from the activation of postsynaptic alpha,beta-adrenergic and P2X-purinergic receptors and under some conditions, NPY1 receptors. Neurotransmitter release is modulated by presynaptic alpha2-adrenergic receptors and possibly also P2X-purinoceptors. The major postsynaptic subtypes involved were well predicted by mRNA expression as measured by RT-PCR, suggesting that this technique may be a useful adjunct to studies aimed at identifying functional receptor subtypes.

Pathway-specific effects of calcitonin gene-related peptide on irideal arterioles of the rat

1. Arteriolar diameter and membrane voltage have been measured to investigate the actions of calcitonin gene-related peptide (CGRP) in rat irideal arterioles. 2. Activation of sensory nerves inhibited sympathetic vasoconstriction, reduced the accompanying 40-50 mV depolarization by 90% and caused a 4 mV hyperpolarization. 3. The inhibition of vasoconstriction was prevented by either preincubation in L-NAME (10 microM), to inhibit nitric oxide production, by preincubation in the cell-permeant adenylate cyclase inhibitor dideoxyadenosine (1 mM) or by preincubation in the ATP-sensitive potassium channel blocker glibenclamide (10 microM). The subsequent addition of a nitric oxide donor to the glibenclamide solution inhibited nerve-mediated vasoconstriction, suggesting that the potassium channel involvement preceded the production of nitric oxide. The small hyperpolarization was not affected by L-NAME. 4. Nerve-mediated vasodilatation persisted in the presence of L-NAME (10 microM) but was abolished with the CGRP1 receptor antagonist CGRPS-37. 5. In arterioles preconstricted with the alpha 2-adrenoceptor agonist UK-14304 (100 nM), exogenous CGRP caused a hyperpolarization and a dose-dependent vasodilatation, neither of which was affected by L-NAME (10 microM). 6. In arterioles preconstricted with 30 mM KCl, CGRP (10 nM) caused vasodilatation but not hyperpolarization, suggesting that the hyperpolarization was not causal to the vasodilatation. 7. Forskolin (30 nM), in the presence of L-NAME to present effects due to nitric oxide, caused vasodilatation. 8. These results suggest that CGRP inhibits sympathetic nerve-mediated vasoconstriction through sequential increases in cyclic AMP and nitric oxide, while vasodilatation results from increases in cyclic AMP alone. The production of nitric oxide, but not its mechanism of action, appears to be dependent on the activation of ATP-sensitive potassium channels. The possible sites of action of these two pathways are discussed.

A role for neuropeptide Y in rat iridial arterioles

A role for neuropeptide Y (NPY) in neurotransmission in rat iridial arterioles has been investigated. Reverse transcription-polymerase chain reaction analysis has demonstrated mRNA expression for both Y1 and Y2 receptors in the superior cervical ganglion and iris. The Y1 agonist [Leu31,Pro34]NPY caused a dose-dependent constriction of iris arterioles (50% effective concentration of 10(-8) M), but, at low concentrations (10(-9) and 10(-10) M), it failed to potentiate either submaximal responses to norepinephrine (10(-6) M) or submaximal, noradrenergic responses to nerve stimulation. In contrast, 10(-7) M [Leu31,Pro34]NPY potentiated submaximal, noradrenergic responses to nerve stimulation (10 Hz, < or = 1 s) and to a concentration of norepinephrine (10(-7) M) which produced only small contractions. The Y1 antagonist 1229U91 blocked contractions induced by [Leu31,Pro34]NPY. Stimulation of the nerves for longer periods (10 or 20 Hz; 5, 30, or 60 s) revealed a component of the response which was reduced by 1229U91. This component was not apparent after brief stimuli (10 Hz, < or = 1 s), even when opposing receptor pathways were blocked. The Y2 agonist N-acetyl-[Leu28,Leu31]NPY24-36 had little effect on arterioles preconstricted with either high potassium or an alpha 2-adrenoceptor agonist, or on nerve-mediated contractions. Results suggest that NPY, released from sympathetic nerves during long-duration, high-frequency stimulation, activates Y1 receptors on iris arterioles to produce vasoconstriction and to potentiate responses to low concentrations of norepinephrine.

Role of maxi-K+ channels in endothelin-induced vasoconstriction of mesenteric and submucosal arterioles

The action of endothelin in small intestinal resistance vessels of the guinea pig was studied by examining submucosal arteriole vasoactivity in vitro and electrical properties of mesenteric arteriole smooth muscle cells. Endothelin-1 (ET-1) constricted submucosal arterioles with a half-maximal effective concentration of 170 pM. ET-3 caused detectable constriction with a minimum of 20 nM. The ET-1 response was prolonged, with a time to 90% relaxation of 41 +/- 2.8 min after washout. The ETA antagonist BQ-123 (200 nM) decreased the sensitivity to ET-1 approximately 40-fold. Arterioles preconstricted with prostaglandin F2 alpha did not relax when superfused with ET-1, ET-3, or an ETB agonist, IRL-1620, and pretreatment with the nitric oxide synthase inhibitor NG-monomethyl-L-arginine was ineffective in countering ET-1-induced constriction, indicating the absence of functional ETB receptors. Resting membrane potential in isolated cells was characterized by transient hyperpolarizing spikes (THs). ET-1 (20 nM) increased TH frequency and caused the emergence of a larger amplitude population. Under voltage clamp, spontaneous transient outward currents (STOCs) were seen that reversed at the K+ equilibrium potential. ET-1 increased STOC frequency and amplitude. Iberiotoxin (IBTX; 200 nM), a maxi-K+ channel antagonist, blocked the ET-1-induced THs and reduced STOC activity. IBTX or tetraethylammonium increased the rate and extent of ET-1-induced arteriole constriction. We suggest that ET-1-induced vasoactivity of ileal resistance arterioles involves ETA receptor-mediated early activation of maxi-K+ channels that serves to counter strong constriction.

Electrical properties of iridial arterioles of the rat

When intracellular recordings were made from iridial arterioles, the cells had membrane potentials of about -65 mV and perivascular nerve stimulation evoked a membrane depolarization. When these cells were labeled with lucifer yellow, all cells that responded to perivascular nerve stimulation had the morphological characteristics of smooth muscle cells. Cells with the morphological characteristics of endothelial cells were never stained. When impaled with two separate recording electrodes, the smooth muscle layer was shown to form an electrical syncytium with a membrane time constant of approximately 80 ms and an electrical length constant of approximately 900 microns. At the ultrastructural level, areas of close apposition were frequently observed between adjacent smooth muscle cells and between adjacent endothelial cells. On the other hand, at contacts between smooth muscle and endothelial cells, the membranes characteristically had much larger separations. The observations show that individual smooth muscle cells are electrically coupled to their neighbors, but the morphological studies raise the possibility that in these arterioles the endothelial and muscle layers are electrically separate.

Existence, properties, and functional expression of "Maxi-K"-type, Ca2+-activated K+ channels in short-term cultured hepatocytes

A large-conductance, Ca2+-activated K+ channel was identified and characterized in embryonic chick hepatocytes using the patch-electrode voltage-clamp technique. The channel conductance was 213 pS in excised patches bathed in symmetrical 145 mM KCI and 1 mM Ca2+. Current-voltage relationships were linear with high K+ on both sides of the membrane but showed constant field rectification as the K+ gradient was increased. The reversal potential shifted 58 mV per 10-fold change in the ratio of external to internal K+. Channel openings occurred at potentials higher than +50 mV in cell-attached patches. The open probability X voltage relationship shifted to more negative potentials in excised, inside-out patches exposed to a solution containing high Ca2+. The voltage sensitivity of the channel was not significantly affected by changes in internal Ca2+ concentration. Conversely, channel gating, reflected in the half-activation potential, shifted 118 mV per 10-fold change in internal Ca2+ at concentrations less than approximately 2 microM, although at higher Ca2+, this parameter was Ca2+ insensitive. Channel open probability in cell-attached patches increased significantly following exposure of the cells to either the Ca2+ ionophore A-23187 or L-alanine, a cell-volume modulator. Channel density increased with time spent in culture from no observations in 10-hr cells, through 13 and 80% of patches in 24-and 48-hr cultured cells, respectively. The implications of delayed functional expression for ion channel studies in acutely dissociated cells is discussed.

Transient expression of alpha-1B adrenoceptor messenger ribonucleic acids in the rat superior cervical ganglion during postnatal development

We have examined the developmental profile of the alpha-1 and alpha-2 adrenergic receptor messenger ribonucleic acids expression in the rat superior cervical ganglion. The expression of the six messenger ribonucleic acids was studied using reverse transcription-polymerase chain reaction. At four weeks, the dominant messenger ribonucleic acids transcripts in this sympathetic ganglion were alpha-1C, alpha-2A, alpha-2B and alpha-2C. The expression of alpha-1 genes in the superior cervical ganglion appears to be regulated during postnatal development in that two alpha-1 (alpha-1B, alpha-1C) genes were expressed at birth, three, seven and 14 days postnatal but no amplified product for alpha-1B was detected at 28 days and in the aged animals, while the alpha-1C transcript continued to be expressed. No amplified product for alpha-1D was detected in superior cervical ganglion at any of the ages studied. While all three alpha-2 genes were expressed in the superior cervical ganglion at four weeks the dominant alpha-2 messenger ribonucleic acids transcript expressed in the superior cervical ganglion was alpha-2A. This pattern of alpha-2 adrenoceptor gene expression was maintained from birth, throughout development and into old age. These results suggest that the expression of alpha-1 adrenergic receptors in the superior cervical ganglion is regulated developmentally while the expression of alpha-2 genes remains unchanged.

Variation in mRNA expression of alpha-adrenergic, neurokinin and muscarinic receptors amongst four arteries of the rat

Different mechanisms mediate constriction and dilation in different vascular beds. We have used reverse transcription-polymerase chain reaction to investigate whether specific patterns of receptor gene expression may underlie these variable responses. Total RNA, from the basilar, pulmonary, mesenteric and tail arteries of anaesthetised adult Wistar rats, was reverse transcribed and amplified using primers specific for the molecular subtypes of the alpha 1(A, B, D)- and alpha 2(A, B, C)-adrenergic, neurokinin (NK1-NK3) and muscarinic (m1-m5), receptors. Results showed that the pattern of gene expression was variable with no two arteries having the same receptor profile. Messenger RNA for the alpha 1A, alpha 1B, alpha 2B, NK1, NK3, m3 and m5 receptor subtypes were detected in all vessels studied while the remaining subtypes showed a variable expression amongst the arteries. This is the first description of mRNA for the m5 muscarinic receptor in peripheral tissue. The NK3 receptor was the major neurokinin receptor expressed in all vessels except the pulmonary artery, in which the NK1 receptor was also strongly expressed. We conclude that each artery expressed a specific receptor array which may permit some unique neural and hormonal controls.

Alpha-adrenergic, neurokinin and muscarinic receptors in rat mesenteric artery; an mRNA study during postnatal development

Developmental studies show that the innervation of autonomic targets is accompanied by increases in the density of receptors, maturation of receptor-signalling pathways and changes in receptor subtype. The innervation of the rat mesenteric artery occurs over the first 3 postnatal weeks. In this study, we investigated whether alterations in receptor gene expression may underlie physiological changes recorded during development and maturity in this vessel. Total RNA, from mesenteric arteries of rats at birth and postnatal days 7, 14, 28, 240 and 360, was reverse transcribed and amplified using primers specific for the alpha 1 (A, B, D)- and alpha 2 (A, B, C)-adrenergic, neurokinin (NK1-NK3) and muscarinic (m1-m5) receptors. Results showed that all receptor genes expressed at 28 days, except the alpha 1D-adrenergic receptor, were already expressed at birth. Some receptor subtypes showed no change in their relative expression, always being either strongly (alpha 1A, alpha 2B, NK3) or weakly (alpha 2A, alpha 2C, NK1) expressed. Relative to the expression of these receptors, others showed a developmental increase in expression up to 14 days postnatal (alpha 1B, alpha 1D, m2, m3, m5) but no further change with maturity. These latter changes coincide with the development of sympathetic and sensory nerve plexuses in the mesenteric artery, but do not correlate with the physiological changes seen during development and ageing.

Alpha-adrenoceptor activation of a chloride conductance in rat iris arterioles

Changes in membrane potential associated with alpha-adrenoceptor-mediated contraction of rat iris arterioles after nerve stimulation (10 Hz, 1 s) have been measured with conventional intracellular recording techniques. Two different types of intracellular responses were recorded. Cells that show a depolarization are proposed to represent the arteriolar smooth muscle cells because the characteristics of the depolarization are correlated with those of the contraction. Cells that show no response or a small hyperpolarization in response to nerve stimulation are proposed to represent the endothelial cells of the arteriole. Both the depolarization and the contraction were abolished by tetrodotoxin (1 microM), benextramine (10 microM), and prazosin (0.1 mM), indicating that they result from nerve-mediated activation of alpha-adrenoceptors. A small but significant part of the contraction (30%) and the depolarization (11%) was nifedipine sensitive (10 microM). Caffeine (1 mM) abolished the contraction and reduced the depolarization by one-half. Reducing the external chloride concentration also abolished the contraction and reduced the depolarization by 90%. Flufenamic acid (250 mM) abolished both the contraction and the depolarization. It is suggested that, in iris arterioles, the activation of synaptic alpha-adrenoceptors leads to the release of intracellular calcium that activates both the chloride channels in the cell membrane leading to depolarization and the intracellular contractile apparatus leading to vasoconstriction.

Sensory nerves play an efferent role in the function of the arterioles, but not the dilator muscle, of the rat iris

We have studied the expression, distribution and function of receptors for the sensory neurotransmitters, substance P (SP) and calcitonin gene-related peptide (CGRP) in the dilator muscle and arterioles of the rat iris. Immunohistochemical studies showed that the sensory fibres containing these peptides are distributed throughout the connective tissue stroma of the iris and in association with the larger arterioles, but do not come into close association with the dilator muscle cells. Using reverse-transcription polymerase chain reaction, we have shown that both NK1 and NK3 receptor message is expressed by iris tissue, comprising both dilator muscle and stromal tissue. Binding sites for the NK1 agonist, [Sar9, Met(O2)11]-substance P (SarSP), and for CGRP are confined to the stromal layer and to the larger arterioles within that layer and do not appear to be associated with the dilator muscle itself. Application of either SarSP or CGRP produced both a vasodilatation and an inhibition of sympathetic nerve-induced vasoconstriction of the larger arterioles. Neither SarSP nor CGRP altered the resting tone of the dilator nor were they capable of modulating the contractions due to sympathetic nervous activity. These results suggest that the sensory fibres perform an efferent role in the larger irideal arterioles while their presence in the irideal stroma appears not to modulate the activity of the dilator muscle.

Local knowledge and rural mental health reform

Rural mental health care reform has failed to recognize that service utilization and access is guided by the meanings and explanations that rural dwellers ascribe to symptoms and treatments for mental illness. These meanings and explanations are described here as local knowledge. It is argued that planning for reform in rural mental health service delivery must take into account the local knowledge and explanations for mental illness and its treatment in order to improve rural mental health.