PubMed Health⌕ Search

Biomedical subjects

G L Avanzino

Publications and source records attributed to G L Avanzino.

At least 19 recordsLinked to original sources
PubMed1990

Cardiovascular effects of microinjection of ANF and brain natriuretic peptide into ventrolateral medulla.

Cardiovascular effects of microinjection of atrial natriuretic factor (ANF) into 77 sites of the ventrolateral medulla (VLM) were investigated in urethan-anesthetized rats. Changes in mean arterial pressure (MAP) and heart rate (HR) in response to injections of glutamate into these sites were used to determine that they contained cardiovascular neurons. ANF (20 nl of 10(-7) M) decreased MAP [-8.9 +/- 1.5 (SE) mmHg] and HR [-9.0 +/- 2.8 (SE) beats/min] in 5 of 36 vasopressor sites identified by glutamate located in the more rostral and lateral aspect of the rostral VLM (RVLM); no effect was elicited in the other 31 RVLM sites. ANF decreased MAP (-10.4 +/- 2.4 mmHg) and HR (-9.8 +/- 3.0 beats/min) in 25 of 41 depressor sites distributed throughout the caudal VLM (CVLM); no response was observed in the other 16 CVLM sites. Brain natriuretic peptide (BNP) was microinjected (20 nl of 10(-7) M) in 21 VLM sites, before or after microinjection of ANF. BNP and ANF elicited similar results in 17 sites, a decline in MAP and HR in 10 sites, and no effect in 7 sites. In the remaining four cases ANF caused a decline in MAP and in HR, whereas BNP had minimal or no effect. Cardiovascular responses to ANF microinjection into the RVLM and CVLM support the hypothesis that ANF is involved in the transmission of baroreceptor information from the nucleus tractus solitarii to these medullary regions. The similarity of the results obtained with BNP and ANF suggests that these peptides may serve similar roles in medullary pathways involved in the control of the cardiovascular system.

Animals↗
PubMed1987

Effects of corticosterone on neurones of the locus coeruleus, in the rat.

The effects of microelectrophoretic application of corticosterone (CS) on single neurones of the locus coeruleus (LC) were investigated in rats under urethane anaesthesia. Ejecting currents generally ranged from 10 to 60 nA. CS produced an excitatory effect in 73% of the neurones and no effect in 27%. The prevailingly excitatory effects induced by CS on LC neurones may be related to the regulation of those complex events, which constitute the 'stress response'.

Animals↗
PubMed1987

Effects of corticosterone on neurons of reticular formation in rats.

The effects of microelectrophoretic application of corticosterone (CS) on single neurons of the brain stem reticular formation (RF) were investigated and then compared with the effects produced on the same neurons by intravenous administration of CS. The experiments were done in two groups of rats, one anesthetized with urethan and the other with pentobarbital sodium because these anesthetics cause different increases of basal concentration of plasma CS. Microelectrophoretic application of CS to neurons in the caudal portion of RF caused primarily excitatory effects, whereas inhibitory effects were observed in neurons of the rostral portion of the RF. The intravenous injection of CS (5 micrograms/100 g body wt) always produced the same effects as microelectrophoretic application. Under our experimental conditions the increase in plasma CS concentration produced by the intravenous injection of CS was found to be within the physiological range for the rat. The different anatomical distribution of units within the RF responding with either excitation or inhibition may be related to functional differences of the two RF areas.

Animals↗
PubMed1983

Actions of microelectrophoretically applied glucocorticoid hormones on reticular formation neurones in the rat.

The effects of microelectrophoretic application of hydrocortisone (HC) and corticosterone (CS) on single neurones of the brainstem reticular formation (RF) were investigated in rats under urethane anaesthesia. Ejecting currents generally ranged from 5 to 20nA. HC and CS behaved similarly in that they produced an excitatory effect in 26% and 24% of the neurones, respectively, an inhibition in 15% and 17% and no effect in 59% of neurones. The excitatory effects predominated in the caudal portion of the FR and the inhibitory effects in the rostral RF. The different distribution of the effects may be related to functional differences between the two RF areas.

Animals↗
PubMed1979

[Current developments on the physiology of the cardiac atrial pacemaker an excitation conduction of the left atrium].

According to recent developments the atrial pacemaker area and the right atrium show a peculiar morpho-functional organization, i.e.: 1) The pacemaker area is formed of clusters of cells containing relatively few myofibrils and showing embryologic characteristics. Such cells are known as nodal cells and between these and the atrial muscles are in general situated transitional cells. Each cluster is separated from the other by collagenous boundaries. The resistance of the membranes to the current flow seems to be relatively low between the cells of the same cluster but the collagenous boundaries are, according to TRAUTWEIN e UCHIZONO (1963), very poor conductors. The pacemaker activity seems to originate inside the various clusters. 2) The functional relationships between the sinoatrial node and the atrioventricular node as well as the interatrial relationship would take place through preferential pathways. These pathways corresponding approximately to the tracts described by JAMES (1966) (anterior, posterior and middle internodal tracts) and to the interatrial or Bachmann bundle, seems to show a higher velocity conduction. In general the fibres of which the tracts are composed are neither morphologically nor functionally isolated from the atrial muscle. The functional consequences of the above mentioned nodal and atrial organization seems to be: a) The possible conditioning of the pacemaker functions by the various clusters activity i.e. the dominance of one cluster over another. b) The shifting of the pacemaker activity from one cluster to anothr due to the arrival of nervous stimuli or chemical substances, etc. According to some Authors as a consequence of the shift the pacemaker area can sometimes move out side the nodal tissue and settle inside an area belonging to the internodal pathways. c) Another consequence of the shift can be the different involvement of the conducting pathways which can lead to a change in the dynamics of the atrial invasion by the excitement.

Acetylcholine↗