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PubMedDate not supplied

[Multineuronal activity of the basolateral portion of the amygdala in rabbits under conditions of NaCl microinjections into the lateral preoptic field and water deprivation].

A study of the multineuronal activity of the rabbit basolateral amygdala has shown that both a microinjection of NaCl solution into the lateral preoptic field and water deprivation result in the appearance of high-amplitude spikes in the pattern of recorded activity. After microinjection these spikes proceeded with a high frequency. Consumption of water blocked this activity not immediately, but only in a day to three days under conditions of the animal's unrestrained access to water and food. The data obtained point to the arrival of information on drinking to the amygdala; they also imply the formation of certain relationships between LPF and the amygdala.

Amygdala↗

PubMed1996

[Effect of microinjection of neurotensin into hypothalamic paraventricular nucleus on gastric acid secretion in rats].

Effects of microinjection of neurotensin (NT) into the hypothalamic paraventricular nucleus (PVN) on gastric acid secretion were investigated in urethane-anesthetized rats. The results were as follows: NT microinjection into PVN produced a dose-dependent decrease in gastric acid output (GAO); this inhibitory effect of NT was completely blocked by icv pretreatment with the alpha-adrenergic receptor antagonist phentolamine or after bilateral cervical vagotomy, suggesting that the effect may be related with activation of alpha-adrenergic receptors in the nucleus and mediated by vagal nerves.

Adrenergic alpha-Antagonists↗

PubMed1998

Effects of nicotine and mecamylamine microinjections into the nucleus accumbens on ethanol and sucrose self-administration.

Nicotine (NIC) and ethanol (ETOH) are both drugs of abuse that can affect similar pathways in the central nervous system. However, the role of nicotinic processes in ETOH's reinforcing actions is unclear. Although the mesolimbic dopamine systems are known to be involved in the reinforcing effects of ETOH, the role of nicotinic receptors within the nucleus accumbens (NAc) in ETOH reinforcement has not been studied. To address this issue, adult male Long-Evans rats were initiated to self-administer ETOH (10% v/v, n = 14) using the sucrose-substitution procedure or sucrose (5% w/v, n = 8) in a 30-min operant session. They were then surgically implanted with bilateral stainless-steel guide cannulae to allow for microinjection into the core of the NAc. After recovery from surgery, presession microinjections of NIC (0.3, 3.3, 10, 30, and 60 microg/1 microl/brain) or the antagonist mecamylamine (MEC) (1, 3, 10, 30, and 60 microg/1 microl/brain) were performed prior to an ETOH or sucrose self-administration session. NIC (3.3 and 60 microg/microl) and MEC (30 microg/microl) both reduced ETOH self-administration behavior, without affecting sucrose-reinforced behavior. A reduction in the total duration of ETOH responding (termination) was also observed after either 60 microg/microl of NIC and 30 microg/microl of MEC. The lack of a clear dose-response relationship for the agonist and the antagonist indicates that the interaction between the NAc nicotinic system and ETOH self-administration is complex.

Acetylcholine↗

PubMed1997

[Inhibition of gastric motility by microinjection of CCK-8 into rat amygdala].

Intranulear microinjection and electrical stimulation technique were employed to evaluate the effect of ventromedial hypothalamus (VMH) on the gastric inhibition elicited by basomedial amygdala nucleus (BMA) excitation. The results were as follows: (1) Microinjections of CCk-8 (50 ng/microliter) into bilateral BAM resulted in significant decrease in intragastric pressure (IGP) and gastric motility frequency (GMF) (P < 0.01). (2) Neither CCK-A receptor antagonist [L364, 718] nor CCK-8 receptor antagonist [L365, 260] induced effects on IGP or GMF when given alone. (3) If bilateral BMA were pretreated with [L364, 718], CCK-8 could no longer induce any inhibitory effects, whlie [L365, 260] had no similar suppressive effect. (4) The inhibitory effects were not found in other nuclei in the amygdaloid body, such as bed nucleus of the stria terminalis intramygdaloid (BSTIA) and amygdaloid nucleus medial (Me). (5) Electrical stimulation of unilateral VMH or BMA would result in the inhibition of IGP and GMF. (6) After electric coagulation of VMH unilateraly injection of CCK-8 to or stimulation of homolateral VMH could no longer inhibite IGP or GMF. The above results suggest that in BMA CCK-8 exerts inhibitory effect on both motility and intragastric pressure through CCK-A receptors.

Amygdala↗

PubMed1998

Insertional mutagenesis in transgenic mice generated by the pronuclear microinjection procedure.

Insertional mutagenesis in transgenic mice is a powerful method to study structure/function relationships between individual genes and complex developmental traits in the whole organism. Unlike spontaneous or chemical-induced mutations, insertional mutations have the advantage that the mutant locus is "tagged" with the transgene and, therefore, readily accessible at the molecular level. Starting with the work on the limb deformity locus, we describe here the characterization of several mouse mutants generated by insertional mutagenesis with the pronuclear microinjection procedure. These transgenic lines have proven to be ideal as models for human disease and for studying the function of novel genes during development. We also describe the unique features of insertional mutations that arise in transgenic mice produced with the pronuclear microinjection procedure and provide recommendations on how to clone and characterize these mutations at the molecular level. Finally, we discuss future prospects for the use of this unique form of germline mutagenesis in the mouse.

Animals↗

PubMed1993

Developmental anomalies of Xenopus embryos following microinjection of SPARC antibodies.

The function of SPARC (Secreted Protein, Acidic, Rich in Cysteine) in early embryonic development was assayed by microinjecting affinity-purified antibodies directed against SPARC into the blastocoel cavity of Xenopus embryos. Microinjection of SPARC antibodies did not appear to interfere with development until late neurulation. By hatching, a broad spectrum of external developmental anomalies were observable, including bent embryonic axes, accentuated ventral masses, shortened embryonic axes, and lack of visible eye pigment. Histological sections of injected embryos demonstrated that lack of visible eye pigmentation was often associated with deformities in eye development. Bending and shortening of the embryonic axis was associated with highly disorganized myotome patterns and loss of segmental boundaries. The results indicate a requirement for SPARC in the early morphological development of several tissues in Xenopus.

Animals↗

PubMed1993

Modification of the phalangeal pattern of the digits in the chick embryo leg bud by local microinjection of RA, staurosporin and TGF beta's.

Many experimental studies show that in the avian chick limb the digits are specified at early stages of development by characteristic concentrations within the limb mesoderm of a still unidentified morphogen diffusing from the posterior margin of the bud, linked with a specific pattern of homeobox gene expression. In all these studies, digits are distinguished by their size, morphology and phalangeal pattern rather than by their position within the autopodium. In this work we report the induction of digits that have otherwise normal morphology but lack an interphalangeal joint. This suggests that the patterning of these joints is not necessarily linked to the control of the outgrowth of the digital rays. Missing interphalangeal joints were induced by microinjection into the third interdigital space of the leg bud of stage 28 to 31 chick embryos of retinoic Acid (RA), staurosporine and TGF beta 1 and beta 2, but not by microinjection of FGF or EGF. Our results also suggest that the pattern of insertion of the long tendons and the formation of the flexor cutaneous pad at the plantar surface of the digits are both linked to the establishment of the interphalangeal joints.

Alkaloids↗

PubMed1989

Isolation of Mycoplasma bovis from intact and microinjected preimplantation bovine embryos washed or treated with trypsin or antibiotics.

Incubation of day 7 bovine embryos with 10(4) or 10(6) CFU/ml of Mycoplasma bovis (M. bovis) or microinjection of M. bovis into the cells of day 7 embryos did not influence embryonic development. M. bovis was recovered from all embryos washed 10 times by a standard pipetting method or vortexed and pipeted 10 times. M. bovis was also recovered from zonae pellucidae removed and washed from microinjected embryos. Neither treatment with trypsin nor exposure of embryos to combinations of penicillin, streptomycin, lincomycin and spectinomycin, or gentamicin, tylosin, lincomycin, and spectinomycin, inactivated M. bovis.

Animals↗

PubMed1999

Axonal and dendritic transport in Purkinje cells of cerebellar slice cultures studied by microinjection of horseradish peroxidase.

Axonal and dendritic transport in single Purkinje neurons of cerebellar slice cultures was quantified as single transport distances. Examination of the cells within a vital tissue was regarded as being an approach to the in situ condition. The Purkinje cells were organotypically integrated in the in vitro tissues and extended long axonal projections connecting synapses to the target neurons. The tracer horseradish peroxidase (HRP) was applied via microinjection to the somata of the Purkinje cells and the injected neurons were incubated thereafter for defined time-intervals. The tracer was transported anterogradely into the neuron processes. The measurements on both the axonal and the dendritic transport of microinjected HRP revealed continuous transportation with increasing times of postincubation. This transport was reduced by the use of microtubule-depolymerizing drugs. The axonal transport of the tracer was either retarded in colchicine-treated cells or continuously reduced for up to 50% in vinblastine-treated neurons. Thus, a correlation of axonal transport to the microtubules was demonstrated. The dendrites were filled with the tracer after 60 min of postincubation. Dendritic transport was reduced by the use of vinblastine, and not significantly by colchicine. The results strongly support the dependence of neuronal transport on microtubules as a component of the cytoskeleton.

Animals↗

PubMed1978

Reversible hyperphagia and obesity following intracerebral microinjections of colchicine into the ventromedial hypothalamus of the rat.

Colchicine, a drug which produces a reversible inhibition of intraaxonal transport and synaptic transmission, was used as a reversible neural blocker to investigate the role of the ventromedial hypothalamus (VMH) in the control of ingestive behavior and body weight regulation. Male Sprague-Dawley rats received intracranial microinjections of colchicine into the VMH. Volume and concentration of the colchicine solution were varied to assess specificity of action and dose-response relationship. When colchicine (2 and 4 microgram) was microinjected bilaterally into the VMH, there was a dose-dependent increase in food and water intakes and body weight gain which lasted several days. The acute period of hyperphagia was followed by a marked depression in feeding which persisted until body weight was lowered to control levels. This suppression of feeding appeared to be a consequence of the preceding period of hyperphagia and obesity, since colchicine-treated rats which were pair-fed with controls to prevent obesity continued to maintain normal food intake and body weight gain when later fed ad libitum. The results of this study confirm the importance of the VMH in the long term regulation of feeding, and indicate that reversible neuronal blocking with colchicine is a useful technique for investigating the neural substrates of feeding and other behaviors.

Animals↗

PubMed1980

Effects of focal electrical stimulation and morphine microinjection in the periaqueductal gray of the rat mesencephalon on neuronal activity in the medullary reticular formation.

Neurons in the medullary reticular formation (MRF; nucleus reticularis gigantocellularis and nucleus reticularis paragigantocellularis) were evaluated for their involvement in the analgesia produced by focal electrical stimulation and microinjection of morphine into the periaqueductal gray region (PAG) of the rat mesencephalon. Analgesia-producing PAG stimulation altered the spontaneous activity of 80% of the neurons in the MRF (both excitation and inhibition were observed) and inhibited the noxious-evoked excitation of 75% of MRF neurons. Microinjection of morphine into the PAG also increased (50%) and decreased (17%) the spontaneous activity of MRF units and inhibited the noxious-evoked excitation of 47% of MRF neurons. These effects were specific for analgesia produced by the PAG manipulations and were partially reversed by naloxone. The role of the MRF in PAG-induced analgesias and the degree of overlap in neuronal systems influenced by intracranial morphine and electrical stimulation is discussed.

Animals↗

PubMed1983

Analgesia produced by microinjection of L-glutamate into the rostral ventromedial bulbar nuclei of the rat and its inhibition by intrathecal alpha-adrenergic blocking agents.

Definite and dose-dependent analgesia followed microinjection of L-glutamate into the nucleus reticularis paragigantocellularis (NRPG) of rats. This analgesic effect was inhibited by lumbar intrathecal pretreatment with phenoxybenzamine and phentolamine but not by propranolol, methysergide or naloxone. Microinjection of L-glutamate into the nucleus raphe magnus (NRM) also produced an analgesic effect which was reduced by intrathecal pretreatment with methysergide but not by phentolamine. These findings provide direct evidence that the NRPG and NRM function separately in descending pain-suppression systems of the spinal cord.

Adrenergic alpha-Antagonists↗

PubMed1985

Microinjection of neurotensin into the ventral tegmental area produces hypothermia: evaluation of dopaminergic mediation.

Neurotensin-producing perikarya and fibers have been identified in the ventral tegmental area of the rat, and recent microinjection studies indicate that neurotensin may function in the ventral tegmental area to regulate body temperature. In this study, the hypothermic response produced by intraventral tegmental injection of neurotensin was shown to be dose-dependent, with a threshold dose between 0.25 and 0.75 micrograms. When fluphenazine, a dopamine receptor antagonist, was microinjected into various forebrain nuclei simultaneous with neurotensin infusion into the ventral tegmental area, it was found to block neurotensin hypothermia. In contrast, injection with fluphenazine into the nucleus accumbens, lateral septum or preoptic area did not alter the hypothermic response. Furthermore, injection with atropine, phentolamine or diphenhydramine into the diagonal band of Broca did not block neurotensin hypothermia. Neurotensin was also injected directly into the preoptic region and shown to produce hypothermia. However, concurrent infusion of fluphenazine with neurotensin into the preoptic region did not attenuate neurotensin hypothermia. These data are consistent with the postulate that neurotensin acts in the ventral tegmental area to enhance dopamine release in the diagonal band of Broca, thereby producing hypothermia. However, neurotensin-induced hypothermia occurring after injection into the preoptic area does not appear to involve dopamine systems.

Animals↗

PubMed1986

Involvement of the midbrain reticular formation in self-injurious behavior, stereotyped behavior, and analgesia induced by intranigral microinjection of muscimol.

Bilateral microinjection of muscimol (60 ng), a gamma-aminobutyric acid (GABA) agonist, into the central region of the substantia nigra (pars reticulata) produced self-injurious behavior (SIB), stereotyped behavior and analgesic-like effects in rats. Bilateral electrolytic lesions of the midbrain reticular formation ventrolateral to the periaqueductal gray matter completely blocked the SIB but had little effect on stereotyped behavior produced by intranigral muscimol. Lesions of the midbrain reticular formation reduced the antinociceptive effect of intranigral muscimol on the tail-flick but not on the hot-plate test. Bilateral microinjection of muscimol (10-100 ng) into the midbrain reticular formation produced intense stereotyped behavior and had an analgesic-like effect on the hot-plate test but not on the tail-flick test. Stereotyped behavior appeared to interfere with the paw-lick response on the hot-plate test. These data suggest that the antinociceptive effect of intranigral muscimol on the tail-flick test is mediated by fibers that project to or pass through the midbrain reticular formation and that analgesia may play an important role in muscimol-induced SIB. The midbrain reticular formation does not appear to be involved in the stereotyped behavior produced by intranigral muscimol.

Animals↗

PubMed1987

Cardiovascular effects of microinjections of adenosine analogs into the fourth ventricle of rats.

Rats were implanted with chronic indwelling cannulae into the posterior region of the fourth ventricle. After recovery from surgery, acute experiments on blood pressure were conducted under urethane anesthesia. The blood pressure and heart rate responses following administration of two adenosine analogs, NECA and L-PIA were examined. Microinjections of both analogs produced dose-dependent reductions in blood pressure and heart rate. NECA was approximately 20-fold more potent than L-PIA in reducing blood pressure and depressing heart rate. The cardiovascular effects of both analogs were antagonized by parenteral injections of caffeine. These findings show that microinjections of analogs of adenosine into the fourth ventricle can influence areas of the central nervous system involved in cardiovascular control.

Adenosine↗

PubMed1990

Cardiovascular and muscle tone changes produced by microinjection of cholinergic and glutamatergic agonists in dorsolateral pons and medial medulla.

Cardiovascular and muscle responses to L-glutamic acid (Glut) and cholinergic agonists injected into the dorsolateral pontine tegmentum and medial medullary reticular formation (MMRF) were examined in unanesthetized, decerebrated cats. Glut, or cholinergic agonists acetylcholine (ACh) or carbachol (Carb), were injected into pons and MMRF at sites from which electrical stimulation produced bilateral suppression of muscle tone. Glut injection in MMRF produced hypotension without change in heart rate at doses as low as 1 mM. At higher doses (0.1-0.4 M), Glut induced hypotension with bradycardia in 23 out of 40 injections in both pons and MMRF. High concentrations of microinjected Glut decreased muscle tone or produced complete atonia in pons and rostral MMRF. Both N-methyl-D-aspartic acid (NMDA) and non-NMDA receptor blockers attenuated or completely blocked the cardiovascular response, while only non-NMDA antagonists blocked muscle inhibition to Glut injection. Microinjection of cholinergic agonists produced consistent hypotension in all of the injections in pons and MMRF, however, the heart rate response was variable with increase (27/42), decrease (2/42), or no change (13/42) in rate seen. Cholinergic injection produced muscle atonia in pons and caudal MMRF but not in rostral MMRF. Both muscle and cardiovascular responses were blocked by atropine but not by hexamethonium. The time course of muscle atonia and cardiovascular change differed in most of the experiments. We conclude that muscle tone suppression and cardiovascular response to Glut or cholinergic agonists use different receptor mechanisms and possibly different neurons. However, the co-localization of these mechanisms suggests that neuronal networks in the medial medulla and dorsolateral pons coordinate motor and cardiovascular responses.

Animals↗

PubMed1981

Influence of body temperature on the epileptogenic effect of enkephalin microinjections into the hippocampus.

The influence of different body temperatures on the epileptiform discharges induced in hippocampus by local microinjections of leu-enkephalin was studied in rats. In the absence of enkephalin, changes in body temperature by either cooling or heating induced epileptiform discharges that disappeared after temperature stabilization. The epileptiform episode induced by enkephalin microinjections was of longer duration at temperature below normal (29-30 degrees C). At body temperature above normal (39-40 degrees C) the epileptiform discharge was less intense and of shorter duration. In vitro testing led to parallel results: the destruction of enkephalin by the brain tissue was faster at higher temperatures. It is proposed that in conditions of hyperthermia enkephalin has a weaker activity due to acceleration of the activity of peptidases involved in its breakdown.

Animals↗

PubMed1985

Analgesic effects of cyclazocine and morphine microinjected into the rat dorsomedial hypothalamus demonstrated by the bradykinin-induced flexor reflex test.

The analgesic effect of cyclazocine microinjected into the diencephalon of rats was studied by using the bradykinin-induced flexor reflex test. The dorsal portion of the medial hypothalamic area was sensitive to cyclazocine with respect to the production of analgesia (ED50 2.6 micrograms/rat). Microinjections of morphine into the same portion also produced a dose-dependent analgesic effect (ED50 2.5 micrograms/rat). As naloxone (0.9 mg/kg s.c.) antagonized both these analgesic effects, the findings suggest that the dorsal portion of the medial hypothalamic area of the rat is one of the primary target sites of analgesic drugs.

Animals↗