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Z Y Tong

Publications and source records attributed to Z Y Tong.

12 recordsLinked to original sources
PubMed2003

Mouse prostasin gene structure, promoter analysis, and restricted expression in lung and kidney.

Human prostasin is a membrane-anchored serine peptidase hypothesized to regulate lung epithelial sodium transport. It belongs to a unique family of genes on chromosome 16p11.2/13.3. Here we describe genomic cloning, promoter analysis, and expression of prostasin's mouse ortholog. The 4.3-kb mouse prostasin gene (prss8) has a six-exon organization identical to human prostasin. Prss8 spans two signal tagged-sites localized to chromosome 7. Multiple mRNA transcripts arise from two consensus initiator elements of a TATA-less promoter and an alternatively spliced, 5' untranslated region intron. Reporter assay establishes that the initiator elements and a GC-rich domain comprise the core promoter and identifies 5' flanking regions with strong enhancer and repressor activity. The 3' untranslated region overlaps the 3' untranslated region of the Myst1 gene oriented tail-to-tail at this locus. Prss8 is highly transcribed in pancreas, kidney, submaxillary gland, lung, thyroid, prostate, and epididymis, and is developmentally regulated. Using selective riboprobes and antibodies to mouse prostasin, we localized its expression to lung airway epithelial and alveolar type II cells and kidney cortical tubule epithelium. Mouse prostasin highly resembles its human ortholog in gene organization and tissue specificity, including strong expression in pulmonary epithelium, suggesting that mice will be useful for probing prostasin's functions in vivo.

3' Untranslated Regions↗
PubMed2000

Up-regulation of tyrosine hydroxylase mRNA in a sub-population of A10 dopamine neurons in Parkinson's disease.

Neuronal injury has been consistently found in A10 midbrain dopamine neurons in Parkinson's disease (PD). To assess changes in neurotransmitter-related gene transcription, in these neurons in PD, tyrosine hydroxylase (TH) mRNA expression was examined in the ventral tegmental area (VTA) of seven PD cases and seven control subjects, using in situ hybridization histochemistry (ISHH). In controls, TH mRNA expression was found in both melanised and non-melanised neurons in the VTA. Neither population expressed dopamine beta-hydroxylase (DBH). Of the melanised neurons, 99% were TH mRNA positive. The level of the TH mRNA signal (expressed as grain density per cell) was similar in the two populations (melanised: 0.129+/-0.004 (mean+/-S.E.M.), n=142 vs. non-melanised: 0.138+/-0.006, n=89, P>0.05, Student's t-Test). In PD cases there was no significant change in TH mRNA expression in melanised neurons (0.138+/-0.003, n=196), and the proportion of positively labeled melanised neurons was 98%. However, non-melanised neurons showed significantly higher TH mRNA (0.163+/-0.006, n=87) than non-melanised neurons in control subjects (P<0.005) and melanised neurons in the PD cases (P<0.0005). This up-regulation of TH mRNA expression in non-melanised neurons may suggest the existence of a compensatory mechanism at presynaptic level.

Aged↗
PubMed1998

Do non-dopaminergic neurons in the ventral tegmental area play a role in the responses elicited in A10 dopaminergic neurons by electrical stimulation of the prefrontal cortex?

It is rapidly becoming apparent that the prefrontal cortex (PFC) plays a major role in controlling the activity of midbrain dopaminergic (DA) neurons. We have previously demonstrated that electrical stimulation of the PFC elicits inhibition-excitation (IE) and excitation (E) activity patterns in DA neurons in the ventral tegmental area (VTA; A10 cell group). Since non-DA neurons in the VTA are cortically innervated, synapse upon DA neurons and appear to have an inhibitory impact, we determined the extent to which the responses of these neurons to stimulation of the PFC could account for the responses seen in DA neurons upon cortical stimulation. Stimulation of the PFC (0.25 mA and 1.0 mA) elicited three categories of response in the majority of VTA non-DA neurons. Types I and II were characterised by a short-to-moderate latency excitation (referred to as "early excitations"), in the latter case preceded by inhibition. Type III responses consisted of inhibition in the absence of an early excitation. Elements of these responses were compared with the temporal characteristics of key elements of responses elicited in DA neurons by PFC stimulation. Although the early excitations in non-DA neurons preceded the inhibitions in DA neurons exhibiting IE responses, the early excitations began approximately 100 ms before the inhibitions in DA neurons and often ended several tens of milliseconds before the inhibitions began, making a causal relationship between these events unlikely. The inhibitions in Type III responses, combined with the inhibitions which followed the early excitations in many Type I and II responses, showed temporal characteristics that suggested a possible causal relationship with the excitations in DA neurons exhibiting E responses, but not those exhibiting IE responses. However, since the excitatory phases of E and IE responses appear to be homologous, the lack of involvement of non-DA neurons in the excitatory phase of IE responses tends to cast doubt on the involvement of non-DA neurons in the excitation during E responses. In fact, the most coherent impression that emerges is that non-DA neurons in the VTA do not influence the activity of A10 DA neurons on a short time-scale (i.e. phasically), but instead may influence activity on a longer time-scale (i.e. tonically).

Action Potentials↗
PubMed1996

Preferential occupation of mineralocorticoid receptors by corticosterone enhances glutamate-induced burst firing in rat midbrain dopaminergic neurons.

Sensitisation to the behavioural effects of amphetamine, a phenomenon which appears to involve the potentiation of excitatory amino acid (EAA)-mediated transmission at the level of dopaminergic (DA) neurons in the ventral tegmental area (the A10 cell group), is known to be affected by corticosteroid manipulations. Since there is evidence that corticosteroid manipulations can also influence unpotentiated EAA-mediated transmission elsewhere in the brain, the possibility was examined that the same may be true for midbrain DA neurons. The effect of iontophoretically administered glutamate on the activity of A10 DA neurons was investigated in adrenalectomised animals given a low dose of corticosterone intravenously (equivalent to 13.4 micrograms/100 ml plasma - likely to preferentially occupy the mineralocorticoid subtype of corticosteroid receptor) at least 45 min (median 132.5) prior to recording. Cells from these animals were compared to those from adrenalectomised and sham operated animals administered saline. Adrenalectomy significantly reduced the firing rate of A10 cells, and this effect was reversed by corticosterone replacement. Adrenalectomy did not affect basal burst firing. However, in those cells which could be classified as "bursting' under basal conditions, cells from animals administered corticosterone showed enhanced glutamate-induced bursting relative to the other two groups. The degree of enhancement was strictly determined by the basal bursting level of the cell. Since the distinction between "bursting' and "non-bursting' DA neurons is probably not related to differences at the level of the EAA receptor/effector mediating bursting, it is argued that corticosterone's facilitation of glutamate-induced bursting is not produced at this level, but rather at the level of an intrinsic membrane property which modulates bursting.

Adrenalectomy↗
PubMed1996

Stimulation of the prefrontal cortex in the rat induces patterns of activity in midbrain dopaminergic neurons which resemble natural burst events.

Evidence suggests that excitatory amino acid-containing afferents from the prefrontal cortex (PFC) play an important role in the induction of burst firing in midbrain dopaminergic (DA) neurons. In the present study, the extracellular activity of individual DA neurons (A10 and A9 cell groups) was recorded during single pulse electrical stimulation (0.25 and 1 mA) of the PFC. The majority of cells were responsive, and two main patterns of activity were elicited: responses characterised by an initial excitation (E responses; 41.8% of responses at 0.25 mA and 26.6% at 1 mA; cell groups combined) and responses characterised by excitation following an initial inhibition (IE responses; 43.3% of responses at 0.25 mA and 56.6% at 1 mA; cell groups combined). Burst analysis performed on the excitatory phase of E and IE responses revealed that the excitation contained events which fulfilled the criteria for natural bursts in DA neurons. A procedure was developed for assessing whether these bursts were time-locked to the stimulus. This showed that 27.9% of E responses and 33.3% of IE responses were accompanied by time-locked bursts (currents and cell groups combined). It is argued that time-locked bursts during IE responses were produced by rebound activation of a low threshold calcium conductance, whereas time-locked bursts during E responses were produced by excitatory afferents. Since natural bursts in DA neurons also seem to involve cortically induced excitation, the hypothesis that the PFC plays a role in the production of natural bursts in DA neurons is strengthened.

Animals↗
PubMed1996

A pharmacological analysis of the burst events induced in midbrain dopaminergic neurons by electrical stimulation of the prefrontal cortex in the rat.

Electrical stimulation of the prefrontal cortex produces an inhibition-excitation (IE) activity pattern in the majority of responsive midbrain dopaminergic neurons. The excitatory phase often contains events, time-locked to the stimulation, which resemble natural bursts. The present study investigated the relationship between the inhibition and time-locked bursts by reducing the impact of the inhibition through membrane hyperpolarisation with the dopamine agonist apomorphine (i.v.) or antagonism with the GABAA antagonist picrotoxin (i.v. and iontophoretic). Apomorphine abolished or reduced time-locked bursting in all IE cells. Picrotoxin reduced the initial inhibition in the majority of IE cells, and abolished or reduced time-locked bursting at the highest intravenous dose. However, reductions in the initial inhibition were not systematically related to reductions in time-locked bursting. Hence, the phenomena do not appear to be causally related. Instead, time-locked bursts appear to be based on a straightforward excitation, which makes them closely analogous to natural bursts.

Animals↗
PubMed1996

Antagonism of NMDA receptors but not AMPA/kainate receptors blocks bursting in dopaminergic neurons induced by electrical stimulation of the prefrontal cortex.

Evidence suggests that the prefrontal cortex (PFC) plays an important role in the burst activity of midbrain dopaminergic (DA) neurons. In particular, electrical stimulation of the PFC elicits patterns of activity in DA neurons, closely time-locked to the stimulation, which resemble natural bursts. Given that natural bursts are produced by the activity of excitatory amino acid (EAA)-ergic afferents, if PFC-induced time-locked bursts are homologues of natural bursts, EAA antagonists should attenuate them. Hence, the NMDA (N-methyl-D-aspartate) antagonist CPP (3-((+/-)-2-carboxypiperazin-4-yl)propyl-1-phosphonic acid) and the AMPA (D,L-alpha-amino-3-hydroxy-5-methyl-4-isoxalone propionic acid)/kainate antagonist CNQX (6-cyano-7-nitroquinoxaline-2,3-dione) were applied by iontophoresis to DA neurons exhibiting time-locked bursts during PFC stimulation. CPP produced a significant reduction in time-locked bursting. In contrast, CNQX (at currents which antagonised AMPA responses) did not. These effects of CPP and CNQX on time-locked bursting mirror the effects previously reported for these drugs on natural bursting. Since natural bursting and bursting induced by PFC stimulation are both blocked selectively by CPP, the present results increase the degree of analogy between the two burst phenomena, thereby adding extra support to the contention that the cortex is involved in producing the natural bursting in DA neurons.

6-Cyano-7-nitroquinoxaline-2,3-dione↗
PubMed1995

Chronic administration of (+)-amphetamine alters the reactivity of midbrain dopaminergic neurons to prefrontal cortex stimulation in the rat.

Repeated intermittent administration of (+)-amphetamine produces sensitisation to many of the behavioural effects of the drug. Evidence suggests that excitatory amino acidergic projections from the prefrontal cortex (PFC) to dopaminergic (DA) neurons in the ventral midbrain may be partly involved in the maintenance of sensitisation once induced. The present study was designed to investigate whether chronic amphetamine administration produces any alteration to this input, by assessing the impact of single pulse electrical stimulation of the PFC (0.25 and 0.5 mA) on the extracellular activity of individual midbrain DA neurons in drug and vehicle treated rats. Animals were administered amphetamine according to a schedule known to produce sensitisation (2.5 mg/kg free base, once daily for 6 days; s.c.), and the effect of PFC stimulation was assessed on withdrawal days 2 and 10. In addition to single spike firing patterns, the ability of the stimulation to elicit stimulus bound (time-locked) burst events was also noted. In the majority of cases, the elicited responses could be broadly categorised into two types--ones characterised by an initial excitation (E responses) and ones characterised by excitation following an initial inhibition (IE responses). On withdrawal day 2, IE responses were affected such that, in those responses which contained time-locked bursts in their excitatory phases, the stimulus produced a time-locked burst on a greater percentage of trials. On withdrawal day 10, the principal change was that E responses were more likely to occur in amphetamine-treated animals than controls (0.25 mA; 57.1% vs. 41.2% of responses, respectively; 0.5 mA; 36.7% vs. 23.5% of responses, respectively). It is argued that an increase in the proportion of excitatory responses in drug animals indicates a potentiation of the excitatory drive to the DA neurons. Insofar as sensitisation in the longer term relies upon an enhancement of amphetamine-induced dopamine release in the forebrain, this may be one mechanism by which it is achieved.

Amphetamine↗
PubMed1993

Time sampling observation procedure for studying drug effects: interaction between d-amphetamine and selective dopamine receptor antagonists in the rat.

A rapid time sampling observation procedure combined with two forms of automatic activity assessment is described. The methods are illustrated by examination of the behavioral effects of d-amphetamine, administered to rats either alone or in combination with antagonists selective for D1 or D2 dopamine (DA) receptors. Low doses of d-amphetamine (0.5-4.0 mg/kg) increased photocell counts, rearing, ambulation, and various forms of sniffing. Similar effects were observed in the first 30 min following administration of 8.0 mg/kg d-amphetamine. However, animals exhibited licking, intense sniffing down, and repetitive head and limb movements in the following 30 min; minimal ambulation, rearing, and sniffing up were observed. The "traditional" total photocell count measure did not differentiate between these time-dependent changes in locomotion. On the other hand, latch counts-where subjects had to move between the beams to register a count-adequately demonstrated this change in locomotion. The selective D1 receptor antagonist SCH23390 and selective D2 antagonist raclopride dose dependently inhibited the behavioral changes produced by 1.5 mg/kg d-amphetamine. Higher doses of SCH23390, but not raclopride, produced a behavioral pattern indistinguishable from that observed in control sessions. Both DA antagonists equipotently blocked the intense sniffing down and repetitive head/body movements produced by 8.0 mg/kg d-amphetamine. A narrow intermediate range of doses of SCH23390 reduced the incidences of these behaviors and produced levels of locomotion and sniffing straight that were significantly higher than those observed in control session. This form of behavioral activation was not observed with raclopride. Therefore, this observation procedure revealed subtle differences between the inhibitory effects of SCH23390 and raclopride on d-amphetamine-induced behavioral changes.

Animals↗
PubMed1991

Effects of low, autoreceptor selective doses of dopamine agonists on the discriminative cue and locomotor hyperactivity produced by d-amphetamine.

The ability of low doses of the dopamine (DA) agonists quinpirole and (+)-3-PPP to reduce the discriminative stimulus properties and locomotor hyperactivity produced by d-amphetamine (0.5 mg/kg) was assessed in two groups of rats. Quinpirole (0.0125-0.05 mg/kg) and (+)-3-PPP (1.0-2.0 mg/kg) completely antagonized d-amphetamine-induced locomotor hyperactivity. In contrast, only single doses of quinpirole (0.025 mg/kg) and (+)-3-PPP (2.0 mg/kg) were effective in the drug discrimination paradigm; the antagonisms were small (18-47%), but significant. The inhibitory effects of quinpirole and (+)-3-PPP in these behavioural models are probably due to their ability to selectively stimulate DA autoreceptors in the nucleus accumbens and reduce the increase in DA release produced by d-amphetamine. It is suggested that the much weaker effects of the drugs in the discrimination paradigm are due to changes produced by the long-term periodic administration of d-amphetamine to these animals, such as a down-regulation in the sensitivity of DA autoreceptors.

Animals↗
PubMed1991

Behavioural profile of partial D2 dopamine receptor agonists. 1. Atypical inhibition of d-amphetamine-induced locomotor hyperactivity and stereotypy.

The effects of partial D2 dopamine (DA) receptor agonists on the behavioural activation produced by 1.5 and 8.0 mg/kg d-amphetamine were compared with the changes produced by the classical DA antagonist haloperidol. Alterations in behaviour were assessed in standard activity monitoring cages by direct observation of the rats using a rapid time sampling procedure. Haloperidol blocked d-amphetamine (1.5 mg/kg)-induced increases in photocell counts, ambulation, rearing and sniffing up, and after the highest dose of the DA antagonist the animals were mainly inactive. The partial D2 DA agonist SDZ 208-911 was equipotent to haloperidol in blocking the increase in photocell counts and rearing produced by d-amphetamine. However, even high doses of the drug did not reduce the incidence of sniffing or induce inactivity, but qualitative changes in the form of sniffing did occur. Although considerably less potent, preclamol exerted similar effects to SDZ 208-911. The profiles of SDZ 208-912 and terguride were intermediary to those of SDZ 208-911 and haloperidol. All compounds blocked the repetitive sniffing down produced by 8.0 mg/kg d-amphetamine. After a low dose of haloperidol, these stereotyped behaviours were replaced by a behavioural syndrome similar to that observed with low dose d-amphetamine, but inactivity was observed following a further small increase in antagonist dose. The blockade of stereotypy by SDZ 208-911, preclamol and terguride was accompanied only by the low dose d-amphetamine behavioural syndrome; no inhibition of sniffing or induction of inactivity occurred. SDZ 208-912 exhibited a profile with features very similar to that noted with haloperidol. These findings suggest that partial D2 agonists exert similar, but not identical, behavioural effects to classical DA antagonists when dopaminergic function in increased by d-amphetamine. The differences in behavioural profile are discussed in relation to variations in the intrinsic efficacy of the dopaminergic compounds and to differences in the response capability of D2 receptor populations underlying the different behaviours produced by d-amphetamine.

Animals↗