Biomedical subjects

J Ciriello

Publications and source records attributed to J Ciriello.

At least 73 records · Page 4Linked to original sources

PubMed1987

Ventral pallidum projections to mediodorsal nucleus of the thalamus: an anatomical and electrophysiological investigation in the rat.

Horseradish peroxidase (HRP) and single unit recording experiments were done in rats to investigate neural connections from the ventral pallidal region to the mediodorsal nucleus of the thalamus (MD). In the first series, following the diffusion or iontophoretic injection of HRP into the MD, retrogradely labeled neurons were observed throughout the rostrocaudal extent of the ipsilateral ventral pallidum. Most of the labeled neurons were found in an area between the nucleus of the diagonal band and the ventral aspect of the substantia innominata subcommissuralis. Additional labeled neurons were found in the ventral aspect of the globus pallidus and substantia innominata sublenticularis. In the second series, the region shown to contain labeled neurons was explored for single units antidromically activated by single pulse stimulation of the MD in urethane anesthetized rats. One hundred and fifty-nine single units in the subpallidal area were antidromically activated with latencies corresponding to conduction velocities of 0.2-3.9 m/s. A greater percentage of units in the subcommissural region (50.3%) were activated antidromically as compared to the sublenticular region (27.4%). In the third series, the MD was explored for single units which responded orthodromically to stimulation of the ventral pallidum. Fifty-eight percent (40/69) of MD units responded to stimulation of the subcommissural substantia innominata, whereas 90% (72/80) MD units responded to stimulation of the sublenticular substantia innominata. The most frequent type of orthodromic response observed in MD neurons was inhibition with short onset latencies (less than 10 ms). These data provide anatomical and electrophysiological evidence for the existence of direct pathways from the ventral pallidum to the MD and suggest that this projection is part of a corticosubcortical loop through which the frontal cortex with the ventral striatum and pallidum may contribute to motor function.

Animals↗

PubMed1987

Effect of preganglionic stimulation on neuropeptide-like immunoreactivity in the stellate ganglion of the cat.

In pentobarbital-anesthetized cats, treated with hexamethonium and atropine, 40 Hz stimulation of the preganglionic input to the decentralized right stellate ganglion caused cardioacceleration. When the 40-Hz stimulation is maintained for 2 h, this cardioacceleration was progressively attenuated and eventually irreversibly lost. At this time, neurotensin-like and leucine-enkephalin-like immunoreactivity associated with intraganglionic fibers and presumptive axon terminals was also lost. Preganglionic 40 Hz stimulation for 2 h did not change substance P-like, somatostatin-like, vasoactive intestinal peptide-like and corticotropin-releasing factor-like immunoreactivity in the stellate ganglion. A 40-Hz 2-h stimulation of the intact stellate ganglion output caused no change of the neuropeptide immunoreactivity pattern. These findings suggest that neurotensin and leucine-enkephalin are released by sympathetic preganglionic axon terminals and that the releasable pool of these peptides is depleted by prolonged preganglionic stimulation. The association of peptide depletion with loss of the cardioacceleration, evoked by stimulation of the input to the stellate ganglion in the presence of cholinergic antagonists, suggests the possibility that peptides are involved in the non-cholinergic mechanism of ganglionic transmission mediating the cardioacceleration.

Animals↗

PubMed1987

Forebrain mechanisms in neurogenic hypertension.

In recent years a considerable amount of experimental evidence has suggested that forebrain structures are involved in the pathogenesis of high arterial pressure (AP). However, little is known about the location and function of these supramedullary structures in the hypertensive process. This report reviews a series of studies done to identify the location and to determine the contribution of some forebrain structures to both the development and maintenance of the elevated AP following selective aortic baroreceptor deafferentation (ABD). In the first series of studies, it was demonstrated that the elevated AP resulting from ABD was associated with increased metabolic activity in several forebrain structures: the paraventricular nucleus of the hypothalamus (PVH), supraoptic nucleus, nucleus circularis, median preoptic nucleus, subfornical organ (SFO), and central nucleus of the amygdala. In the second series, bilateral electrolytic lesions of the PVH were shown to prevent the development of and (or) reverse the elevated AP after ABD. Similarly, bilateral microinjections of the neurotoxin kainic acid into the PVH were shown to reverse the increased AP after ABD. In the final series, electrolytic lesions of the SFO were shown to attenuate the rise in AP after ABD and (or) to reduce the elevated AP to a level that remained above control values. Taken together, these data suggest that the PVH and SFO are components of a neuronal circuit involved in the hypertensive process following ABD, and that the SFO likely exerts its effect through the PVH.

Animals↗

PubMed1987

Effect of stimulation of afferent renal nerves on plasma levels of vasopressin.

Experiments were done in alpha-chloralose-anesthetized, paralyzed and artificially ventilated cats with vagus, cervical sympathetic, aortic depressor, and carotid sinus nerves cut bilaterally to investigate the effect of afferent renal nerve (ARN) stimulation on circulating levels of vasopressin (AVP). Electrical stimulation of ARN elicited a pressor response that had two components, a primary (1 degree) component locked in time with the stimulus and a secondary (2 degree) component that had a long onset latency and that outlasted the stimulation period. The 1 degree and 2 degree components of the pressor response were largest at stimulation frequencies of 30 and 40 Hz, respectively. Autonomic blockade with hexamethonium bromide and atropine methylbromide abolished the 1 degree component. Administration of the vasopressin V1-vascular receptor antagonist d(CH2)5VAVP during autonomic blockade abolished the 2 degree component. Plasma concentrations of AVP measured by radioimmunoassay increased from control levels of 5.2 +/- 0.9 to 53.6 +/- 18.6 pg/ml during a 5-min period of stimulation of ARN. Plasma AVP levels measured 20-40 min after stimulation (13.6 +/- 7.0 pg/ml) were not significantly different from control values. Plasma osmolality was not altered during the course of the experiment. These data demonstrate that sensory information originating in the kidney alters the release of vasopressin from the neurohypophysis and suggest that ARN are an important component of the neural circuitry involved in homeostatic mechanisms controlling arterial pressure.

Afferent Pathways↗

PubMed1987

Effects of renal receptor activation on neurosecretory vasopressin cells.

Electrical stimulation of afferent renal nerves (ARN) has been shown to excite neurosecretory vasopressin (AVP) cells of the supraoptic nucleus (SON). To investigate the sensory modality of the ARN involved, the present study examined in pentobarbital-anesthetized rats the responses of putative AVP cells to procedures intended to differentially activate renal receptor populations. Neurosecretory SON cells were identified by antidromic invasion from the neurohypophysis and classified as AVP secreting on the basis of spontaneous activity patterns and responses to arterial baroreceptor activation. Neither elevation of systemic arterial pressure (50-100 mmHg, 9 cells) following sinoaortic and cardiopulmonary afferent nerve transection nor renal venous occlusion (15 cells) altered AVP cell discharge. Renal ischemia, produced by renal arterial occlusion (50-120 s, 14 cells), and renal arterial infusion of adenosine (1-50 micrograms, 8 cells) were also without effect. However, infusions into the renal artery of bradykinin (1-3 micrograms) excited 9/15, of capsaicin (1-3 micrograms) excited 13/15, and of sodium cyanide (5-40 micrograms) excited 1/11 AVP cells examined. These data demonstrate that, in the anesthetized rat, putative neurosecretory AVP cells in the SON are responsive to activation of bradykinin- and capsaicin-sensitive renal receptors and suggest that activation of these receptors contributes to the hormonal regulation of the circulation.

Animals↗

PubMed1987

Central organization of afferent renal nerve pathways.

Although afferent renal nerves have been studied for over a quarter of a century, their physiological role remains unclear. There is considerable experimental evidence indicating that afferent renal nerves convey sensory information from renal receptors to integrative circuits in the central nervous system which gives rise to command signals controlling the function of effector organs. In addition, it has been demonstrated that these integrative neural circuits are found at several different levels of the neuraxis; the spinal cord, the medulla and the hypothalamus. In this review, recent neuroanatomical and electrophysiological data on the central pathways of afferent renal nerves is discussed with reference to their possible role in homeostasis.

Afferent Pathways↗

PubMed1986

Immunohistochemical identification of noradrenaline- and adrenaline- synthesizing neurons in the cat ventrolateral medulla.

The distribution and morphology of cell bodies containing the catecholamine biosynthetic enzymes dopamine-beta-hydroxylase (DBH) and phenylethanolamine N-methyltransferase (PNMT) in the ventrolateral medulla (VLM) of the cat were studied immunohistochemically after intracisternal administration of colchicine. Perikarya immunoreactive to DBH were found throughout the VLM extending from approximately the spinomedullary junction to the level of the superior olivary nucleus. In the caudal VLM DBH neurons were found primarily in the region immediately dorsal to the lateral reticular nucleus (LRN), although a few scattered DBH neurons were also found near the ventral surface of the medulla in and around the parvicellular division of the LRN. These DBH neurons in the caudal VLM were generally fusiform, fusiform-bipolar, or multipolar, with a mean somal area of 422 +/- 32 microns2, and with two to four branching processes. In the rostral VLM DBH neurons formed three distinct groups: one group was found in the nucleus paragigantocellularis lateralis in the region just ventromedial to the retrofacial nucleus (RFN) near the ventrolateral surface of the medulla; the second group was found in the region dorsomedial to the rostral aspects of the nucleus ambiguous and the RFN, and the third group was found in the region along the lateral aspect of the superior olivary nucleus. Perikarya immunoreactive to the adrenaline-synthesizing enzyme PNMT were localized to a more restricted region of the VLM that extended from approximately the rostral aspect of the caudal third of the inferior olivary complex (level of the obex) to the caudal pole of the facial nucleus. These PNMT neurons were fusiform or multipolar with a mean somal area of 273 +/- 21 microns2, and with two to five branching processes. The location, size, shape, and numbers of PNMT-immunoreactive neurons corresponded closely to the rostral groups of DBH neurons, with the exception of the group found along the lateral aspect of the superior olivary nucleus. These data indicate that noradrenaline-synthesizing neurons are primarily found in the caudal VLM and in the region near the superior olivary nucleus, whereas catecholamine neurons in the rostral VLM between these two noradrenergic cell groups synthesize adrenaline. As the VLM has previously been shown to have direct connections with spinal cord, brainstem, and hypothalamic areas implicated in cardiovascular and neuroendocrine regulation, this suggests that DBH- and PNMT-synthesizing neurons are components of neuronal circuits involved in these homeostatic mechanisms.

Adrenergic Fibers↗

PubMed1986

Electrophysiological identification of forebrain connections of the subfornical organ.

Experiments were performed in 17 urethane-anesthetized rats to investigate electrophysiologically neurons in the subfornical organ (SFO), which send efferent axons directly to the region of the paraventricular nucleus of the hypothalamus (PVH), the supraoptic nucleus (SON) and the nucleus medianus (NM). Extracellular single unit recordings were made from spontaneously active and silent neurons in the region of SFO (n = 130) and the nucleus triangularis (NT; n = 20). Sixty-five units in SFO were antidromically activated by stimulation of either PVH, SON or NM with latencies corresponding to conduction velocities of 0.54 +/- 0.07 (n = 24), 0.44 +/- 0.05 (n = 17) and 0.23 +/- 0.02 (n = 24) m/s, respectively. Axons of SFO units projecting to NM conducted at significantly slower velocities than those to PVH and SON. An additional 11 units were antidromically activated in NT by stimulation of these forebrain structures. Sixty-seven units were found to respond orthodromically to stimulation of PVH, SON and NM: 58 in SFO and 9 in NT. Orthodromic responses were primarily excitation or inhibition. These data have demonstrated bidirectional pathways between SFO and forebrain structures which are likely involved in the dipsogenic and arterial pressure responses to activation of SFO by blood-borne angiotensin II.

Animals↗

PubMed1986

Changes in plasma catecholamine levels after insula damage in experimental stroke.

The effect of permanent occlusion of the left middle cerebral artery (MCA) on plasma catecholamine levels was investigated in chloralose-anesthetized cats. Two-5 h after occlusion of the MCA the plasma levels of norepinephrine, epinephrine and dopamine were significantly elevated (33%, 44% and 28%, respectively) compared to preocclusion levels only in animals in which the cerebral infarction involved the insular cortex. No significant changes were observed in plasma catecholamine levels in animals in which either the infarction did not involve the insula or in sham-stroked animals. These data suggest that withdrawal of inhibitory inputs from the insula on central cardiovascular regulating centers after stroke results in an increase in the activity of the sympathoadrenal system.

Animals↗

PubMed1986

Bidirectional cardiovascular connections between ventrolateral medulla and nucleus of the solitary tract.

Single-unit recording experiments were done in chloralose-anesthetized, paralyzed and artificially ventilated cats to identify neurons in ventrolateral medulla (VLM) that send efferent axons directly to the region of the nucleus of the solitary tract (NTS) and receive cardiovascular afferent inputs from the carotid sinus (CSN) and aortic depressor (ADN) nerves and the NTS. Units in VLM were identified by antidromic excitation to stimulation of functionally and histologically verified sites in the NTS complex. Antidromic potentials were recorded from 34 units in VLM. Units responded with a mean antidromic latency of 4.37 +/- 0.32 ms corresponding to a mean conduction velocity of 0.93 +/- 0.07 m/s. Of these 34 units, 18 were excited orthodromically by stimulation of the CSN and/or ADN. Furthermore, 10 of the 18 units responding to stimulation of the buffer nerves were also orthodromically excited by stimulation of NTS. An additional 76 units were identified in VLM that only responded orthodromically to stimulation of NTS with a mean latency of 9.75 +/- 2.93 ms, of which 33 also responded orthodromically to stimulation of the buffer nerves. These data provide electrophysiological evidence of a bidirectional connection between neurons in VLM that receive and integrate peripheral cardiovascular afferent inputs and send efferent axons directly back to the region of NTS. These results suggest that neurons in the VLM may be part of a medullary feedback reflex loop through which afferent information from cardiovascular receptors exerts an influence on NTS neurons involved in the control of the circulation.

Animals↗

PubMed1986

Somatostatin-like immunoreactivity in neurons, nerve terminals, and fibers of the cat spinal cord.

The distribution of somatostatin-like immunoreactivity (SS) was studied in the spinal cord of untreated cats and of cats that had received colchicine at all levels of the cord. In the dorsal horn small (less than 15 microns in diameter), round neurons were found in Rexed laminae II and III at all levels. At all levels laminae IV-VI contained smaller numbers of immunoreactive neurons that were medium (between 15 and 25 microns in diameter) to large (greater than 25 microns in diameter) in size. In addition, small numbers of medium-sized neurons were observed at the dorsal and dorsomedial borders of the gray and white matter in segments C1-5. In the sacral cord (S1-3), a group of medium-sized bipolar neurons was found in the dorsolateral funiculus. In transverse sections the processes of the neurons in these two latter groups travelled in a direction parallel to the border of the gray and white matter. In the intermediate and central gray matter, in addition to the immunoreactive neurons found in the region of the intermediolateral nucleus and nucleus intercalatus of lamina VII in segments C8 to L4 (Krukoff et al., '85a), lamina VII contained immunoreactive neurons at all levels with the largest number occurring in the thoracic cord. These neurons were medium to large in size and were generally multipolar with processes travelling in all directions. Multipolar small immunoreactive neurons were also found in the central gray region (lamina X) in the thoracic and upper lumbar cord. Finally, small numbers of neurons containing SS were found in the ventral horn of the cervical and upper thoracic cord. These multipolar neurons were medium to large in size. The distribution of nerve terminals and fibers containing SS was similar to that previously described in mice, rats, guinea pigs, and primates. Although the function of somatostatin in the spinal cord is not known, its presence in neurons with short processes suggests that it may act to modify local activity in the regions where it is found, including areas involved in sensory, visceromotor, and motor functions.

Animals↗

PubMed1986

Function of the ventrolateral medulla in the control of the circulation.

The CNS control of the cardiovascular system involves the coordination of a series of complex neural mechanisms which integrate afferent information from a variety of peripheral receptors and produce control signals to effector organs for appropriate physiological responses. Although it is generally thought that these control signals are generated by a network of neural circuits that are widely distributed in the CNS, over the last two decades a considerable body of experimental evidence has accumulated suggesting that several of these circuits involve neurons found on or near the ventral surface of the medulla oblongata. Neurons in the VLM have been shown to be involved in the maintenance of vasomotor tone, in baroreceptor and chemoreceptor (central and peripheral) reflex mechanisms, in mediating the CIR and somatosympathetic reflexes and in the control of the secretion of vasopressin. These physiological functions of VLM neurons have been supported by neuroanatomical and electrophysiological studies demonstrating direct connections with a number of central structures previously implicated in the control of the circulation, including the IML, the site of origin of sympathetic preganglionic axons, and the SON and PVH, the site of origin of neurohypophyseal projecting axons containing AVP. Considerable suggestive evidence has also been obtained regarding the chemical messengers involved in transmitting information from VLM neurons to other central structures. There have been developments suggesting a role for monoamines and neuropeptides in mediating the neural and humoral control of SAP by neurons in the VLM. This review presents a synthesis of the literature suggesting a main role for VLM neurons in the control of the circulation.

Animals↗

PubMed1986

Changes in forebrain hexokinase activity after aortic baroreceptor denervation.

Although forebrain structures have been implicated in both the development and maintenance of the elevated arterial pressure (AP) after aortic baroreceptor denervation, little is known about the location of central structures involved in the hypertensive process. In the present study, regions of the forebrain whose metabolic activity was altered after aortic baroreceptor denervation were functionally identified using hexokinase (HK) histochemistry in the rat. Three days after bilateral aortic depressor nerve (ADN) transection AP was significantly elevated compared with sham ADN-transected animals (143 +/- 1 and 122 +/- 2 mmHg, respectively). Significant increases in HK activity were observed in the magno- and parvocellular components of the paraventricular nucleus of the hypothalamus, supraoptic nucleus, nucleus circularis, median preoptic nucleus, subfornical organ, and central nucleus of the amygdala in the ADN-transected animals. These data have demonstrated that removal of aortic baroreceptor afferent inputs alters the activity of forebrain structures previously implicated in regulation of body fluid balance and AP and suggest that these structures are involved in the hypertensive process after ADN transection.

Animals↗

PubMed1985

Kainic acid lesions of paraventricular nucleus neurons reverse the elevated arterial pressure after aortic baroreceptor denervation in the rat.

The effect of selective destruction of neurons of the paraventricular nucleus of the hypothalamus (PVH) with kainic acid on the maintenance of the elevated arterial pressure (AP) and heart rate (HR) after aortic baroreceptor denervation was investigated in male Wistar rats. The average AP and HR were significantly elevated in two groups of animals which were subjected to bilateral aortic depressor nerve (ADN) transection compared to sham-ADN-transected animals. Microinjections of kainic acid bilaterally into the PVH-reduced the elevated AP and HR in ADN-transected animals to levels which were not significantly different from either sham-ADN-transected animals which received kainic acid injections into the PVH or from predenervation levels. AP and HR in the sham-ADN-transected animals which received bilateral PVH injections of kainic acid were not altered from prelesioned levels. As magnocellular neurons of the PVH have been shown to be resistant to the neurotoxic effects of kainic acid, these data indicate that PVH parvocellular neurons are required for the maintenance of the elevated AP and HR resulting from the removal of aortic baroreceptor inputs to the central nervous system.

Animals↗

PubMed1985

Lateral hypothalamic and peripheral cardiovascular afferent inputs to ventrolateral medullary neurons.

Experiments were done in chloralose anesthetized, paralyzed and artificially ventilated cats to identify single units in ventrolateral medulla (VLM) projecting directly to the intermediate gray (IG) region of the upper thoracic cord and responding to inputs from pressor sites in the anterior lateral hypothalamus (Hla) and carotid sinus (CSN) and aortic depressor (ADN) nerves. Forty-eight units were antidromically activated in VLM to stimulation of the IG at the level of T2. Of these 48 units, 15 (31%) were orthodromically excited by stimulation of the Hla with a mean latency of 15.8 +/- 2.1 ms. In addition, 8 of the 15 units responding to Hla stimulation were also excited orthodromically by stimulation of either the CSN or ADN or both. Of the remaining 33 units, 15 responded to stimulation of only the buffer nerves and 18 were unresponsive to the tested inputs. These results provide electrophysiological evidence for the existence of neurons in VLM which receive hypothalamic and buffer nerve inputs and suggest that the VLM plays a role in integrating and relaying cardiovascular afferent information from peripheral baroreceptors and chemoreceptors and from supramedullary centers to provide effector signals to spinal autonomic neurons involved in the control of the circulation.

Animals↗

PubMed1985

Segmental distribution of peptide-like immunoreactivity in cell bodies of the thoracolumbar sympathetic nuclei of the cat.

The distribution of leucine-enkephalin, methionine-enkephalin, neurotensin, somatostatin, substance P, oxytocin, vasopressin, and neurophysin II in cell bodies of sympathetic autonomic nuclei of the thoracolumbar (T-L) spinal cord was studied immunohistochemically in cats after intrathecal administration of colchicine. Neurons containing only enkephalin-, neurotensin-, somatostatin-, and substance P-like immunoreactivity (ENK, NT, SS, SP, respectively) were found in the intermediolateral nucleus pars principalis (IMLp) and pars funicularis (IMLf), the nucleus intercalatus (IC), and the central autonomic area (CA). The size, shape, location, and numbers of the peptide-positive neurons in the IMLp, IMLf, and IC suggested that they were sympathetic preganglionic neurons (SPN). This was confirmed by a combined retrograde tracing/immunohistochemical study showing that most of these neurons at the levels of the T-L cord known to provide preganglionic fibers to the stellate ganglion were SPN. On the other hand, the functional identification of the neurons in the CA is uncertain as neurons were not observed which were both retrogradely labelled and contained ENK, NT, SS, or SP. Immunoreactive neurons in each area were counted in ten sections from each segment from C8 to L4. In the IMLp, the SPN with ENK were greatest in number (up to 25) in segments T4-T7 and L2-L3. The maximum number of SPN containing NT was found in segments T4-T7 (45 neurons). Of the four peptides, neurons containing SS were found in the greatest number (up to 48 in segments T2-T6); neurons containing SP were found in the smallest number (15 or fewer per segment). Few SPN containing each of the four peptides were found in the IC; CA neurons with ENK and NT were also few in number. A comparison of the numbers of immunoreactive neurons in the IML with earlier estimates for the total numbers of SPN in the IML at each level showed that the proportions of IML neurons containing each of the four peptides were fairly consistent throughout the T-L cord, with some exceptions. These results suggest that the innervation of visceral organs is not obviously peptide-specific, although some organs may be innervated by a greater proportion of SPN containing one of these peptides. Finally, the presence of ENK, NT, SS, and SP in SPN suggests that these four peptides act as neurotransmitters in preganglionic pathways to sympathetic ganglia.

Animals↗

PubMed1985

Segmental distribution of peptide- and 5HT-like immunoreactivity in nerve terminals and fibers of the thoracolumbar sympathetic nuclei of the cat.

The distribution of leucine-enkephalin, methionine-enkephalin, neurotensin, somatostatin, substance P, oxytocin, vasopressin, neurophysin II, and serotonin in nerve terminals and fibers of sympathetic autonomic areas of the thoracolumbar (T-L) spinal cord was studied immunohistochemically in cats. Densities of these immunoreactive terminals and fibers were estimated in the intermediolateral nucleus pars principalis (IMLp) and pars funicularis (IMLf), the nucleus intercalatus (IC), and the central autonomic area (CA). Results for leucine- and methionine-enkephalin-like immunoreactivity (ENK) were similar and immunoreactivity for vasopressin was not observed. The greatest numbers of terminals and fibers in the IMLp region contained ENK, neurotensin-(NT), and serotonin-like immunoreactivity (5HT); terminals and fibers containing substance P-(SP) and neurophysin II-like immunoreactivity (NP2) were intermediate in number, and those containing somatostatin-(SS) and oxytocin-like immunoreactivity (OXY) were generally sparse. In the IC and CA, terminals and fibers containing ENK and NT were dense, those containing SP were moderate, and those containing OXY, NP2, and 5HT were sparsely represented. In the IMLp, where the largest proportion of sympathetic preganglionic neurons (SPN) is found, the greatest concentration of terminals and fibers containing ENK was found in segments T1-T8; for NT these segments were T1-T5 and T11-L1, for SP-C8-T2 and T11-L1, for NP2-T4-T7 and L2 to L3, and for 5HT-T1-T5. Terminals and fibers containing SS and OXY were present in segments C8-T10 and segments C8, T2-T8, T13, and L2 to L3, respectively. These results indicate that while ENK, NT, SP, NP2, and 5HT fibers and terminals are widely distributed throughout the T-L cord, they may influence to a greater degree the SPN in segments where they are present in greater numbers. As SS and OXY were not found at all levels of the IMLp, their functions may be more organ specific.

Animals↗

PubMed1985

Effect of paraventricular nucleus lesions on arterial pressure and heart rate after aortic baroreceptor denervation in the rat.

Two series of experiments were done in male Wistar rats to investigate the effects of lesions of the paraventricular nucleus of the hypothalamus (PVH) on the maintenance and development of the elevated arterial pressure resulting from denervation of aortic baroreceptors. In the first series, after control recordings of arterial pressure (AP) and heart rate (HR), rats were subjected to either bilateral aortic depressor nerve (ADN) transection or sham-ADN transection. These animals were later subjected to either bilateral lesions of the PVH or sham-PVH lesions. AP (146 +/- 2 mm Hg) and HR (515 +/- 5 bpm) were significantly elevated in only the ADN-transected groups. Bilateral lesions of the PVH significantly reduced AP (119 +/- 3 mm Hg) and HR (440 +/- 8 bpm) in the ADN transected animals compared to ADN-transected sham-PVH-lesioned animals, to levels which were not significantly different from pre-ADN-transected levels (AP, 113 +/- 2 mm Hg; HR, 448 +/- 3 bpm), and from sham-ADN-transected PVH-lesioned (AP, 119 +/- 2 mm Hg; HR, 391 +/- 6 bpm) and sham-ADN-transected sham-PVH-lesioned animals (AP, 116 +/- 2 mm Hg; HR, 436 +/- 4 bpm). In the second series of experiments, after control AP and HR recordings rats were first subjected to either bilateral lesions of the PVH or sham-PVH lesions, and second to either bilateral ADN transection or sham-ADN transection. PVH lesions did not significantly alter the AP and HR from control levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗