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At least 1,351 records · Page 75Linked to original sources
PubMed1989

Kynurenic acid microinjected into the nucleus tractus solitarius of rat blocks the arterial baroreflex but not responses to glutamate.

The selective excitatory amino acid antagonist kynurenic acid was bilaterally microinjected into the nucleus tractus solitarius of rats to determine its effects on the arterial baroreflex and on the cardiovascular responses to glutamate and nonglutamate agonists injected at the same site. Kynurenic acid blocked the responses to N-methyl-D-aspartate and kainate as well as the baroreflex, but did not block the response to glutamate, quisqualate, or acetylcholine. The data may suggest that glutamate is not a neurotransmitter in the baroreflex arc or that only certain glutamate receptors are integral to the baroreflex in the nucleus tractus solitarius.

Acetylcholine↗
PubMed1989

Altered metabolism of rat contralateral sciatic nerve after microinjection into the endoneurium of the ipsilateral sciatic nerve.

Microinjection of substances into the endoneurium of the sciatic nerve is a technique widely used. Because the contralateral nerve is often used as control nerve, we studied the incorporation of [14C]galactose into myelin lipids in normal nerves, saline-injected nerves and their contralateral nerves. Results show that incorporation of radioactivity into contralateral nerve lipids is affected as compared with normal nerves. We conclude that the contralateral nerve of an injected nerve is not a good control.

Animals↗
PubMed1989

Facilitation of retention performance in mice by pretest microinjection of AVP into dorsal or ventral hippocampus: differential influence of the peptide on appetitive task.

Pre-test local microinjection of arginine-vasopressin (AVP) into dorsal or ventral hippocampus resulted in an improvement of retention performance in an appetitively motivated task. Nevertheless, a better improvement appeared when AVP treatment was performed into ventral hippocampus suggesting a higher sensitivity of this part of hippocampus to the action of AVP. To examine a non-specific behavioral action of the peptide, the effect of AVP treatment on locomotor activity was assessed. When the treatment was given into ventral hippocampus, a reduction of locomotor activity was recorded, whereas after AVP injection into dorsal hippocampus, the peptide failed to alter locomotor activity.

Animals↗
PubMed1990

Volume-dependent spatial distribution of microinjected thyrotropin-releasing hormone (TRH) into the medial preoptic nucleus of the rat: an autoradiographic study.

The present study was performed to quantify the distribution of a peptide neurotransmitter after microinjection into the medial preoptic area (POM), using a technique suitable for conscious animal preparations. The results indicate that only 50-nl volumes of injected tracer were sufficiently localized with 77 +/- 9% recovery in the POM. Injections of higher volumes resulted in an increasing spread of tracer into distant anatomical regions and structures, including the needle tract and cerebral ventricles. The amount of tracer localized in the POM decreased to 38 +/- 4% (200 nl) (P less than 0.05) and 14 +/- 8% (500 nl) (P less than 0.05), respectively. The data suggest that the volume of injection is critical for intraparenchymal injections into structures of a diameter of 1mm or less, such as the POM and should not exceed 50 nl in conscious animal preparations.

Animals↗
PubMed1990

Dopaminergic drugs influence the intensity of catalepsy induced by microinjections of carbachol into the reticular formation.

Carbachol microinjections into the mesencephalic and pontine reticular formation in rats induced intense and long-lasting catalepsy. Systemically administered haloperidol potentiated, while apomorphine and L-DOPA reduced the cataleptogenic effect of carbachol. These results indicate the existence of functional relations between the cholinergic cataleptogenic mechanism in the reticular formation and the dopaminergic system. They are interpreted in the light of known anatomical ascending and descending interconnections between the reticular formation and basal ganglia.

Animals↗
PubMed1991

Microinjections of muscimol and bicuculline into the pontine reticular formation modify the sleep-waking cycle in the rat.

The role of gamma-aminobutyric acid (GABA) in the sleep-waking cycle was evaluated by means of microinjections of muscimol and bicuculline into the rat pontine reticular formation (PRF). Muscimol (20 ng) produced a marked increase in wakefulness (70%), a decrease in slow-wave sleep (SWS) (35%) and a remarkable delay in the onset of both SWS and paradoxical sleep, without modifying the percentage of the latter. Bicuculline (4 ng) shortened SWS latency by about 70%. These results suggest that GABAergic transmission in the PRF is involved in the regulation of sleep-waking cycle in the rat.

Animals↗
PubMed1994

Accumbens microinjection of LY 171555 and sulpiride: effects on circling behaviour, in the rat.

In rats with unilateral 6-hydroxydopamine lesions of the substantia nigra (pars compacta) and amphetamine i.p. some parameters of the rotational activity, following intra-accumbens microinjection of D2 agonist (LY 171555) and antagonist (sulpiride), have been analyzed. An increase in the number of turns was observed with LY 171555, whereas sulpiride determined a decrease. The type of circling was also analyzed: D2 agonist induced a very close turn around the central axis of the animal and D2 antagonist a close turn in the centre of the cage. Data were compared with control condition, which exhibited a large turn around the walls of the cage. The results show that pharmacological manipulation of nucleus accumbens influences rotational behaviour with a specific role for D2 receptors.

Amphetamine↗
PubMed1995

Analysis of the phase shifting effects of gastrin releasing peptide when microinjected into the suprachiasmatic region.

The role of gastrin releasing peptide (GRP) in phase shifting circadian rhythms was investigated. Microinjection of GRP into the suprachiasmatic region (SCN) region produced only small changes in the phase of free-running circadian activity rhythms in hamsters housed in constant darkness. However, co-administration of GRP with vasoactive intestinal peptide (VIP) and peptide histidine isoleucine (PHI) produced significantly larger phase delays than GRP alone. These data support the hypothesis that GRP interacts with VIP and PHI within the SCN to induce phase shifts of circadian rhythms.

Animals↗
PubMed1980

Differential effects of intracerebrally microinjected enkephalin analogs on centrally versus peripherally induced pain, and evidence for a facial versus lower body analgesic effect.

[D-Ala2]-Met-Enkephalin and [D-Ala2]-Met-Enkephalinamide were microinjected (10-30 microgram) into the midbrain ventrolateral central gray of rats. The opiate analogs produced profound analgesia in left and right facial areas, and on the hot plate test. The tail-flick test showed significant analgesia, but in a significantly smaller amount than that obtained with noxious face heating. All effects were blocked by naloxone pre-treatment. The drugs had no effect on thresholds for defense responses to high (200 Hz) and low (20 Hz) frequency aversive stimulation in midbrain areas associated with pain perception.

Animals↗
PubMed1986

Microinjection of dopamine agonists into nucleus raphe magnus affects nociception in rats.

Microinjection of the dopamine receptor agonist apomorphine, and to a lesser extent dopamine itself, into the nucleus raphe magnus increased tail flick latency in conscious rats. The hypoalgesia was dependent on the integrity of catecholamine-containing pathways originating near the third ventricle and was diminished by systemic depletion of hydroxytryptamine. No simple neuronal circuitry could explain all the effects observed.

5,6-Dihydroxytryptamine↗
PubMed1986

Brain-stem areas tonically inhibiting dorsal horn neurones: studies with microinjection of the GABA analogue piperidine-4-sulphonic acid.

In barbiturate anaesthetized cats, tonic inhibition of the excitation of lumbar dorsal horn neurones by impulses in unmyelinated primary afferents was measured by reversibly cooling the spinal cord at the thoraco-lumbar junction. Tonic inhibition was reduced by microinjection of the GABA analogue, piperidine-4-sulphonic acid (2.5 nM in 0.5 microliter) mainly at AP -7, L 2-5 and V -8 to -10. This area in the ventrolateral medulla is just ventral to the facial nucleus and has been shown to be important in cardiovascular control, particularly in relation to fear-defence reactions. It is proposed that tonic inhibition of the nociceptive responses of spinal neurones is part of such a reaction in response to the trauma of surgery. Since previous experiments had shown that the ventrolateral medulla was important in spinal inhibition produced by PAG stimulation, these experiments support the proposal that analgesia does not occur in isolation but is part of a complex behavioural response of an animal in a potentially injurious environment.

Action Potentials↗
PubMed1983

Behavioral and neurochemical effects of neurotensin microinjection into the ventral tegmental area of the rat.

The ventral tegmental area of the rat brain has been shown to possess high densities of neurotensin- and dopamine-containing neuronal perikarya. We recently demonstrated that microinjection of neurotensin into the ventral tegmental area produces behavioral hyperactivity similar to amphetamine-induced increase in exploratory behaviors, but lacking stereotypies. In this study, we report that the threshold dose for neurotensin-induced hyperactivity is 0.10-0.25 micrograms neurotensin/side. Either intracerebroventricular injection of haloperidol (5.0 micrograms/lateral ventricle) or destruction of the mesolimbic dopamine system by 6-hydroxydopamine abolishes the behavioral hyperactivity produced by intraventral tegmental injection of neurotensin (2.5 micrograms/side). Using high pressure liquid chromatography with electrochemical detection, we show that neurotensin injection into the ventral tegmental area increases the concentration of dopamine metabolites, 3,4-dihydroxyphenylacetic acid and homovanillic acid in the nucleus accumbens and olfactory tubercles, but not in the striatum. This effect is especially profound in the nucleus accumbens where the threshold dose is less than 0.025 micrograms/side. The ratio of 3,4-dihydroxyphenylacetic acid to dopamine increased in the nucleus accumbens and olfactory tubercles in a dose-dependent fashion (0.025 microgram-2.50 micrograms/side). Neurotensin-induced behavioral hyperactivity correlates positively with neurotensin-induced changes in the ratio of 3,4-dihydroxyphenylacetic acid to dopamine. This study indicates that neurotensin acts in the ventral tegmental area to activate the mesolimbic dopamine system. Further, this activation produces behavioral hyperactivity characterized by an increase in exploratory behaviors. The fact that both immunoreactive neurotensin and neurotensin receptors are found in high concentration in the ventral tegmental area supports the possible physiological significance of this peptide-catecholamine interaction.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1988

Contralateral head movements produced by microinjection of glutamate into superior colliculus of rats: evidence for mediation by multiple output pathways.

One of the major efferent pathways of the superior colliculus crosses midline to run caudally in the contralateral predorsal bundle, innervating targets in the brain stem and eventually reaching the cervical spinal cord. A variety of evidence suggests that this tecto-reticulo-spinal pathway may mediate the orienting movements that can be evoked by tectal stimulation. However, we have recently found that orienting head movements can still be obtained in rats after section of the tecto-reticulo-spinal pathway, implying that additional pathways are also involved. The present study sought to test this implication, by taking advantage of the fact that in rats the cells of origin of the tecto-reticulo-spinal pathway are largely segregated within the lateral part of the stratum album intermediate. It is thus possible to find out whether orienting head movements can be produced by a cell-excitant from tectal regions that contain few cells of origin of the tecto-reticulo-spinal pathway. Hooded rats in an open field were filmed during microinjections of sodium L-glutamate (50 mM, 200 nl) into the superior colliculus, and the films analysed for the appearance of contralaterally directed movements of the head and body. Subsequent histological reconstruction of the injection sites indicated that such movements could be obtained from widespread areas within the superior colliculus, including not only lateral stratum album intermediale but also the deep layers, and parts of the medial superficial and intermediate layers. Moreover, sites in or close to lateral stratum album intermediate often gave circling movements with downward pointing head, whereas some sites outside lateral stratum album intermediale gave sustained immobility with the head pointing contralaterally and upwards. This evidence supports the view that tectal efferent pathways besides the tecto-reticulo-spinal pathway are involved in the control of head movement. In addition, at least some of these pathways are not collaterals of the tecto-reticulo-spinal pathway, since the movements were obtained from collicular regions with few tecto-reticulo-spinal pathway cells. Finally, the results are consistent with the view that different collicular output pathways mediate movements that have different functions.

Animals↗
PubMed1988

Responses resembling defensive behaviour produced by microinjection of glutamate into superior colliculus of rats.

Electrical stimulation of the superior colliculus in rats elicits not only orienting movements, as it does in other mammals, but also behaviours resembling such natural defensive responses as prolonged freezing, cringing, shying, and fast running and jumping. To investigate the location of the cells mediating these behaviours, the superior colliculus was systematically mapped with microinjections of sodium L-glutamate (50 mM, 200 nl), and the resultant behavioural changes as assessed in an open field were analysed for defence-like responses. The main regions that gave defensive behaviour were (i) rostromedial superior colliculus (all layers), and (ii) both medial and lateral parts of the caudal deep layers. Cells in these areas project into the ipsilateral descending pathway. However, the cells of origin of this pathway are also found in collicular regions, such as rostral intermediate gray and parts of far caudal colliculus, that did not give defensive movements in response to glutamate stimulation. It is unclear whether this is because only parts of the ipsilateral pathway mediate defensive behaviours, or because glutamate is a relatively inefficient stimulating agent for these systems. An unexpected feature of the results was that at a number of collicular sites the nature of the defensive response changed with successive (up to three) injections of glutamate, often appearing to become more intense. Whether the mechanism underlying this potentiation is related to the conditioning of natural defensive behaviour is unknown.

Animals↗
PubMed1994

Systemic and regional haemodynamic responses elicited by microinjection of N-methyl-D-aspartate into the lateral periaqueductal gray matter in anaesthetized rats.

The haemodynamic defence responses were studied by chemically stimulating the lateral periaqueductal gray matter in 27 anaesthetized, artificially ventilated, and paralysed rats. Blood flow was measured by the radiolabelled microsphere method. Microinjection of N-methyl-D-aspartate (1 nmol as 100 nl of a 10-mM solution, delivered over 10 s) into the brain region elicited a distinctive pattern of haemodynamic defence responses. Vasodilation of the hindlimb skeletal muscle tended to be provoked from the caudal third of the periaqueductal gray, whereas vasoconstriction was elicited from the intermediate third. Whichever stimulation was made, however, increases in arterial pressure, heart rate, cardiac output, and total peripheral resistance were consistently provoked. The blood flow was redistributed away from the abdominal viscera. One new finding was that the brain and heart also had their blood flow increased consistently, the former with and the latter without a significant decrease in vascular resistance. As suggested for the classic pattern of haemodynamic defence responses, we consider that the cerebral and coronary circulations may also be involved in coping with the emergency that threatens the animal. The increased cerebral blood flow should be beneficial for ensuring adequate achievement of central processing and organization of the well-coordinated defence reactions. The increased coronary blood flow should help to ensure maintenance of an increased cardiac output striving against the increased total peripheral resistance.

Anesthesia↗
PubMedDate not supplied

Stereotaxic implant microinjection and temperature recording system for rabbits.

Modification of standard rabbit stereotaxic apparatus to allow adjustment of the tooth bar in the vertical plane may be accomplished by simple machining of a standard laboratory clamp and aluminum rod. The modification greatly increases speed of head positioning for implant surgery. Machining the chrome and brass luer hub of standard stainless steel hypodermic needles to the described configurations produces improved guide tubes for brain temperature recording and cannulae for brain microinjections. Data from hypothalamic injection of prostaglandin E1 and records of resulting changes in brain temperature support the effectiveness of the methods described.

Animals↗
PubMed1988

Cardiovascular effects of microinjection of adenosine into the nucleus tractus solitarius.

Rats were anesthetized with urethane and limited occipital craniotomy was conducted to expose the caudal medulla in the region of the obex. Microinjections of adenosine were made into the nucleus tractus solitarius and heart rate and blood pressure responses recorded. Adenosine produced dose-related decreases in blood pressure and heart rate. The data indicate that adenosine may play a neuromodulatory role in central cardiovascular control areas.

Adenosine↗