Prefrontal stimulus-produced hypotension in rat

Summary In 41 rats, bipolar electrical stimulation was administered to various regions of the frontal cortex, including the medial prefrontal cortex (MPFC), lateral prefrontal cortex (LPFC), infralimbic cortex, and convexity cortex. Resulting alterations of blood pressure and heart rate were noted. It was observed that hypotension resulted from stimulation administered to either LPFC, infralimbic cortex or ventral portion of MPFC (i.e. prelimbic cortex). Furthermore, stimulation of the LPFC typically produced bradycardia, whereas stimulation of the MPFC or infralimbic cortex had little or no effect on heart rate. Pharmacological and surgical blocks of the vagus nerves failed to attenuate the stimulus produced hypotension (SPH), as elicited from the prefrontal or infralimbic cortices, thus demonstrating that SPH in rats is not mediated by the vagus nerves. However, intraperitoneal injections of norepinephrine, which mimicked a state of increased sympathetic tone, were observed to completely block SPH. Accordingly, it is suggested that SPH may occur as the result of sympathetic inhibition. Furthermore, intravenous injections of naloxone were also observed to also completely block SPH, thus demonstrating that SPH may be mediated via opioid pathways.     

Catalepsy after microinjection of haloperidol into the rat medial prefrontal cortex

Summary To investigate the behavioural role of mesocortical dopamine innervation we performed bilateral microinjections of haloperidol into various parts of the rat frontal cortex and into adjacent subcortical forebrain structures. Haloperidol (2.5 g/ 0.5 l) locally injected into the medial prefrontal cortex or into the rostral part of the neostriatum resulted in the development of catalepsy as measured in the bar test. In contrast, injections of haloperidol into the nucleus accumbens, more caudal parts of the neostriatum, anterior cingulate cortex, rostral and lateral parts of the prefrontal cortex and into the lateral ventricles failed to induce catalepsy. It is concluded that blockade of dopamine receptors located in the rostral neostriatum and in the medial prefrontal cortex contributes to the development of haloperidol induced catalepsy.     

New central projections of neuropeptide FF: colateral branching pathways in the brainstem and hypothalamus in the rat

Neuropeptide FF (NPFF), a morphine modulatory peptide, has been identified within discrete autonomic regions in the brainstem and hypothalamus. Triple fluorescence labelling was employed to identify collateral branching projections of NPFF neurons located within the nucleus tractus solitarius (NTS) and in the region of the hypothalamus between the dorsomedial and ventromedial hypothalamus. Injections of two retrograde tracers, rhodamine- and fluorescein-labelled latex microspheres into the pontine parabrachial nucleus (PBN) and the ventrolateral medulla resulted in labelling of NPFF neurons in the NTS that contained one (double-labelled) or both (triple-labelled) tracers. Within the NTS, most double- and triple-labelled NPFF neurons were localized at the level of the area postrema or just rostral to it and within the medial and dorsomedial subdivisions of the nucleus. Injections of tracers into the PBN and hypothalamic paraventricular nucleus revealed double- and triple-labelled NPFF neurons, a majority of which were located in a zone between the dorsomedial and ventromedial hypothalamus. These results indicate that NPFF neurons in the brainstem and hypothalamus may simultaneously transmit signals to their target nuclei in the brainstem and forebrain. This coordinated signalling may lead to synchronized responses of NPFF target sites and provide insights into the role of this peptide in cardiovascular and nociceptive responses.     

Antagonism of α1-adrenergic and serotonergic receptors in the hypoglossal motor nucleus does not prevent motoneuronal activation elicited from the posterior hypothalamus

The perifornical (PF) region of the posterior hypothalamus plays an important role in the regulation of sleep–wake states and motor activity. Disinhibition of PF neurons by the GABA_A receptor antagonist, bicuculline, has been used to study the mechanisms of wake- and motor activity-promoting effects that emanate from the PF region. Bicuculline activates PF neurons, including the orexin-containing cells that have major excitatory projections to brainstem noradrenergic and serotonergic neurons. Since premotor aminergic neurons are an important source of motoneuronal activation, we hypothesized that they mediate the excitation of motoneurons that results from disinhibition of PF neurons with bicuculline. In urethane-anesthetized, paralyzed and artificially ventilated rats, we found that PF bicuculline injections (1 mM, 20 nl) made after combined microinjections into the hypoglossal (XII) nucleus of α₁-adrenergic and serotonergic receptor antagonists (prazosin and methysergide) increased XII nerve activity by 80 ± 16% (SE) of the control activity level. Thus, activation of XII motoneurons originating in the hypothalamic PF region was not abolished despite effective elimination by the aminergic antagonists of the endogenous noradrenergic and serotonergic excitatory drives to XII motoneurons and abolition of XII motoneuronal activation by exogenous serotonin or phenylephrine. These results show that a major component of XII motoneuronal activation originating in the posterior hypothalamus is mediated by pathways other than the noradrenergic and serotonergic projections to motoneurons.     

Cortical afferents to the prefrontal cortex of the cat: a study with the horseradish peroxidase technique.

Following horseradish peroxidase (HRP) injections into different areas within the prefrontal cortex (PFC) of the cat, labeled neurons were found in the cingulate and insular cortex. These results demonstrate that the cat's prefrontal cortex is reached directly from these cortical regions, and that the observed cortical projections are similar to those detected in the monkey's prefrontal cortex.     

Fever produced in the rat by intracerebralE. coli endotoxin

Summary E. coli endotoxin introduced into the brain ventricles or into various brain areas raises the body temperature of conscious rats. Endotoxin-sensitive sites were found within the anterior hypothalamus and the lower brainstem. The increase in temperature (T) after microinjection of endotoxin into the anterior hypothalamic nucleus was dose-dependent. Endotoxin injected into the ventricles produced monophasic hyperthermia, but microinjections into the anterior hypothalamus produced monophasic or biphasic types of hyperthermia. The second and third microinjections of endotoxin into the anterior hypothalamic nucleus subsequently caused higher responses in T, but not in the rate of temperature change. The effects of the fourth and further microinjections were the same as those of the third, and no tolerance developed for 24 days. The observations of behaviour, vegetative reactions, skin temperature, and carbon dioxide production indicated that the rise in the rat body temperature induced by endotoxin represents fever and that the heat is gained, at an ambient temperature of 22°C, mainly through skin vessel vasoconstriction. Aspirin abolished and reversed fever induced by endotoxin, while hydrocortisone was without effect.     

Hippocampal-prefrontocortical circuits: PKA inhibition in the prefrontal cortex impairs delayed nonmatching in the radial maze in rats

Recent findings implicate the prefrontal cortex (PFC) and, in particular, frontocortical dopamine acting at D1-like receptors, in working memory. However, the mechanisms underlying this function of dopamine remain unknown. The present studies evaluated the hypothesis that dopamine contributes to working memory through its action on the 2nd messenger cyclic 3',5'-adenosine monophosphate (cAMP) and cAMP-dependent protein kinase (PKA). Thus, rats were trained to perform random foraging or delayed (30 min) nonmatching-to-position (delayed win-shift) tasks on the radial maze. With hippocampal output to the frontal cortex disconnected by injecting lidocaine (20 microg/0.5 microl) unilaterally into the ventral subiculum, contralateral frontocortical injections of lidocaine (20 microg/0.5 microl) or the D1-like dopamine receptor antagonist SCH 23390 (0.5 microg/0.5 microl) impaired delayed win-shift but not random foraging, replicating previous findings. In similarly disconnected rats, frontocortical injections of the PKA inhibitor Rp-cAMPS (5.0 and 10.0, but not 1.0, microg/0.5 microl) selectively impaired delayed nonmatching-to-position. Results suggest that activation of the cAMP-PKA pathway by dopamine acting at D1-like receptors in the frontal cortex is necessary for working memory.     

Prefrontal cortex of the cat: Paucity of afferent projections from the parietal cortex

Summary Twenty-one cat brains with cortical injections of horseradish peroxidase resulting in labelled cells in the thalamic mediodorsal nucleus (MD) were screened for afferent projections from the parietal cortex. Contrary to expectation, nearly the whole prefrontal cortex (PFC) situated around the frontal pole was free of parietal afferents, while a small area in the anterior sylvian gyrus (orbito-insular subregion of PFC) consistently received afferents from the parietal cortex. The few afferents projecting to the cortex around the frontal pole originated exclusively from the convexity of the suprasylvian gyrus, while the great majority of the parietal neurons projecting to the anterior sylvian gyrus was situated within the fundus of the suprasylvian sulcus. While the main regions of the prefrontal cortex of the rhesus monkey receive a substantial projection from the parietal lobe, whereas the main regions of the cat's prefrontal cortex are free of afferents from the parietal cortex, possible differences in the parieto-prefrontal organization of both species are discussed. Furthermore, differences between the orbito-insular subregion and the rest of the PFC are emphasized.This study was carried out mainly at the University of Konstanz.Dr. B. Petrovi-Mini was a visiting scientist at the University of Konstanz. Research was supported in part by grant Ma 795 from the Deutsche Forschungsgemeinschaft (DFG)     

Delayed response deficits produced by local injection of bicuculline into the dorsolateral prefrontal cortex in Japanese macaque monkeys

Summary Bicuculline (10–30 g, but usually 30 g) was injected locally into 20 different sites in the dorsolateral prefrontal cortex (PFC) of 2 Japanese macaque monkeys, while they were performing a delayed response task. The task was initiated by the rotation of a handle to a central zone by the wrist joint and consisted of seven periods: an initial waiting period of 0.3 s, a pre-cue period (central green lamp of 1.0 s), a cue period (left or right green cue of 0.3 s), a delay period of 4.0 s (occasionally 1 s), a go period (central red lamp; rotation of the handle to either the left or right zone within 1.0 s), a hold period (holding of the handle in either the left or the right zone), and a final reward period. The parameters of the task performance, such as the frequency of correct trials, the frequency of directional error trials in which the monkeys rotated the handle in an incorrect direction during the go period, and the frequency of omission error trials, in which the monkeys did not rotate the handle during the go period, were examined before and after the injection of bicuculline. The injections of bicuculline induced a burst of multi-neuronal activity around the sites of injection. Within 5 min of an injection into one of 7 different sites in the PFC, three different kinds of performance deficit were observed: 1) an increase in the frequency of error responses during the go period in both left-cue and right-cue trials, after injection into the dorso-caudal portion of the principal sulcus (2 sites); 2) an increase in the frequency of directional error responses during the go period in either left-cue or right-cue trials, after injection into the bottom of the middle principal sulcus (3 sites), and 3) an increase in the frequency of omission of responses during the go period, after injection into the dorsal region of the caudal principal sulcus (2 sites). Injections at the remaining 13 sites did not induce any deficits, although injections into the dorsal bank of the principal sulcus (3 sites) induced a decrease in the frequency of the task trials as a result of prolonged intertrial intervals (ITIs). Our results suggest that locally disturbed neuronal activity in different small areas of the PFC induces different deficits in the performance of the delayed response task. Neuronal activity in different, localized areas of the PFC may be involved in different processes of a performance that is based on spatial short-term memory.Abbreviations BMI bicuculline methiodide - PFC prefrontal cortex - DR delayed response - ITI intertrial interval - NSDE nonselective directional error - SDE selective directional error - OE omission error - CR correct performance - DE directional error     

Participation of the medial reticular formation of the medulla oblongata in the supraspinal control of locomotor and postural activities in the guinea pig

The influence of microinjections of novocaine (15 l of a 2% solution) into the ventromedial areas of the reticular formation of the medulla oblongata on the effects of electrical stimulation of the mesencephalic locomotor region, and of adequate stimulation of the vestibular apparatus, was investigated in experiments on decerebrate guinea pigs. It was demonstrated that such injections are accompanied by a reversible increase in the threshold of stimulation of the region indicated, necessary for the initiation of locomotor rhythmicity, as well as by the suppression of vestibular influences on the activity of the flexor muscles of the extremities. The role of the reticular formation of the brainstem in the supraspinal control of posture and locomotion is discussed.Translated from Fiziologicheskii Zhurnal SSSR imeni I. M. Sechenova, Vol. 77, No. 3, pp. 33–40, March, 1991.     

Intravenous morphine-induced activation of vagal afferents: peripheral, spinal, and CNS substrates mediating inhibition of spinal nociception and cardiovascular responses.

1. Intravenous administration of 1.0 mg/kg of morphine produces inhibition of the nociceptive tail-flick (TF) reflex, hypotension, and bradycardia in the pentobarbital-anesthetized rat. The present experiments examined peripheral, spinal, and supraspinal relays for inhibition of the TF reflex and cardiovascular responses produced by morphine (1.0 mg/kg iv) in the pentobarbital-anesthetized rat using 1) bilateral cervical vagotomy, 2) spinal cold block or mechanical lesions of the dorsolateral funiculi (DLFs), or 3) nonselective local anesthesia or soma-selective lesions of specific CNS regions. Intravenous morphine-induced inhibition of responses of unidentified, ascending, and spinothalamic tract (STT) lumbosacral spinal dorsal horn neurons to noxious heating of the hindpaw were also examined in intact and bilateral cervical vagotomized rats. 2. Bilateral cervical vagotomy significantly attenuated inhibition of the TF reflex and bradycardia produced by intravenous administration of morphine. Bilateral cervical vagogtomy changed the normal depressor response produced by morphine into a sustained pressor response. Inhibition of the TF reflex in intact rats was not due to changes in tail temperature. 3. Spinal cold block significantly attenuated inhibition of the TF reflex, the depressor response, and the bradycardia produced by intravenous administration of morphine. However, bilateral mechanical transections of the DLFs failed to significantly affect either inhibition of the TF reflex or cardiovascular responses produced by this dose of intravenous morphine. 4. Microinjection of either lidocaine or ibotenic acid into the nuclei tracti solitarii (NTS), rostromedial medulla (RMM), or ventrolateral pontine tegmentum (VLPT) attenuated morphine-induced inhibition of the TF reflex. Similar microinjections into either the periaqueductal gray (PAG) or the dorsolateral pons (DLP) failed to affect morphine-induced inhibition of the TF reflex. 5. Microinjection of either lidocaine or ibotenic acid into the NTS, RMM, VLPT, DLP, or rostral ventrolateral medulla (RVLM) attenuated the depressor response produced by morphine, although baseline arterial blood pressure (ABP) was affected by ibotenic acid microinjections in the DLP. In all these cases, the microinjections failed to reveal a sustained pressor response as was observed with bilateral cervical vagotomy. Similar microinjections into the PAG failed to affect the depressor response produced by morphine. 6. The lidocaine and ibotenic acid microinjection treatments also showed that the bradycardic response produced by morphine depends on the integrity of the NTS, RMM, RVLM, and possibly the DLP, but not the PAG or VLPT.(ABSTRACT TRUNCATED AT 400 WORDS)     

Subcortical projections to the prefrontal cortex in the rat as revealed by the horseradish peroxidase technique

The sources and distribution of subcortical afferents to the anterior neocortex were investigated in the rat using the horseradish peroxidase technique. Injections into the prefrontal cortex labelled, in addition to the mediodorsal thalamic nucleus, neurons in a total of fifteen subcortical nuclei, distributed in the basal telencephalon, claustrum, amygdala, thalamus, subthalamus, hypothalamus, mesencephalon and pons. Of these, the projections from the zona incerta, the lateroposterior thalamic nucleus, and the parabrachial region of the caudal mesencephalon to the prefrontal cortex have not previously been described.Different parts of the mediodorsal thalamic nucleus project to different areas of the frontal cortex. Thus, horseradish peroxidase injections in the most ventral pregenual part of the medial cortex labelled predominantly neurons in the medial anterior and dorsomedial posterior parts of the mediodorsal nucleus; injections into the more dorsal pregenual area labelled only neurons in the lateral and ventral parts of the nucleus; injections placed supragenually labelled neurons in the dorsolateral posterior part of the nucleus; and injections into the dorsal bank of the anterior rhinal sulcus labelled neurons in the centromedial part of the nucleus.Several other subcortical nuclei had projections overlapping with that of the mediodorsal thalamic nucleus. Five different types of such overlap were distinguished: (1) cell groups labelled after horseradish peroxidase injections into one of the subfields of the projection area of the mediodorsal nucleus (defined as the prefrontal cortex), but not outside this area (parataenial nucleus of the thalamus); (2) cell groups labelled both after injection into a subfield of the projection area of the mediodorsal nucleus and after injections in a restricted area outside this area (anteromedial, ventral and laterposterior thalamic nuclei); (3) cell groups labelled after injections into all subfields of the mediodorsal nucleus projection area, but not outside this area (ventral tegmental area, basolateral nucleus of amygdala); (4) cell groups labelled after injections into any area of the anterior neocortex, including the mediodorsal nucleus projection area (parabrachial neurons of the posterior mesencephalon); (5) cell groups labelled after all neocortical injections investigated (claustrum, magnocellular nuclei of the basal forebrain, lateral hypothalamus, zona incerta, intralaminar thalamic nuclei, nuclei raphe dorsalis and centralis superior, and locus coeruleus).We can draw the following conclusions from these and related findings. First, because of the apparent overlap of projections of the mediodorsal, the anteromedial and ventral thalamic nuclei in the rat, parts of the prefrontal cortex can also be called ‘cingulate’ and ‘premotor’. Second, on the basis of projections from parts of the mediodorsal nucleus, the prefrontal cortex of the rat can be subdivided into areas corresponding to those in other species. Third, the neocortex receives afferents from a large number of subcortical cell groups outside the thalamus, distributed from the telencephalon to the pons; however, the prefrontal cortex seems to be the only neocortical area innervated by the ventral tegmental area and amygdala. Finally, neither the prefrontal cortex nor the mediodorsal thalamic nucleus receives afferents from regions directly involved in sensory and motor functions.     

Peripheral hypotensive and central hypertensive effects of cimetidine

Rapid intravenous (i.v.) injections of high doses (16–128 mol/kg) of cimetidine induced a short-lasting (5–15 min) hypotension in anaesthetized rats. Diastolic pressure was reduced more than systolic pressure, suggesting vasodilatation. Heart rate was not affected. Diphenhydramine pretreatment (100 mol/kg i.v.) did not antagonize the hypotensive effect of cimetidine. However, in the presence of diphenhydramine, cimetidine induced bradycardia. Intracerebroventricular administration of cimetidine or metiamide (2 mol/rat) increased the blood pressure and heart rate. It is concluded that the hypotension after i.v. cimetidine is mediated by peripheral mechanisms. Since diphenhydramine pretreatment had no antagonistic effect cimetidine-induced hypotension could not be due to indirect H₁-receptor stimulation caused by histamine liberation.     

大白鼠前脑、脑干和小脑向孤束核的纤维投射——HRP法和ARG法研究

本实验用HRP法、WGA—HRP法和ARG法进一步研究了大白鼠前脑、脑干和小脑向孤束核的纤维投射及其局部定位关系。作者发现皮质32及8区、三叉神经脊束核尾侧亚核投射到孤束核头段;皮质24及8a区、三叉神经脊束核尾侧亚核投射到孤束核中段;皮质23及13区,中脑导水管周围灰质和三叉神经脊束核尾侧亚核投射到孤束核尾段。此外,结果还证明室旁核、下丘脑外侧区、兰斑核、K—F氏核、小脑顶核、中缝大核、网状大细胞核、外侧网状核、及延髓网状结构向孤束核的纤维投射,均存在着一定的局部定位关系。本文结合前脑、脑干向孤束核的纤维投射讨论了内脏活动调节及针刺镇痛效应的中枢机理并对大白鼠孤束核的分段(头、中及尾段)标准提出了新建议。     

Midbrain periaqueductal grey region in the cat has afferent and efferent connections with solitary tract nuclei

Wheat germ agglutinin-horseradish peroxidase (WGA-HRP) injections were made at the same sites within the midbrain periaqueductal grey region (PAG) of the cat at which microinjections of excitatory amino acids had previously elicited the set of autonomic and somatic reactions (i.e. pupil dilatation, piloerection, retraction of the ears, arching of the back, hissing, howling and growling) known as the 'defence reaction'. The WGA-HRP injections revealed that this PAG region has an extensive set of afferent and efferent connections with solitary tract nuclei (NTS). Within the NTS the majority of labelled neurons were distributed, in approximately equal numbers, in the ipsilateral medial solitary nucleus (SM) and the ipsilateral and the contralateral ventrolateral solitary nuclei (SVL). The densest anterograde labelling was found in the ipsilateral SM, with lighter anterograde labelling in the contralateral SM and bilaterally in the commissural solitary nucleus and SVL. The described connections between the defence region of the PAG and the NTS not only provide a new anatomical basis for cardiovascular and respiratory components of the reaction, but also add to the evidence that, in addition to the hypothalamus, the PAG is an important integrating center for the autonomic and somatic elements of the defence reaction.     

Anatomical analysis of afferent projections to the medial prefrontal cortex in the rat

The medial prefrontal cortex (mPFC) has been associated with diverse functions including attentional processes, visceromotor activity, decision making, goal directed behavior, and working memory. Using retrograde tracing techniques, we examined, compared, and contrasted afferent projections to the four divisions of the mPFC in the rat: the medial (frontal) agranular (AGm), anterior cingulate (AC), prelimbic (PL), and infralimbic (IL) cortices. Each division of the mPFC receives a unique set of afferent projections. There is a shift dorsoventrally along the mPFC from predominantly sensorimotor input to the dorsal mPFC (AGm and dorsal AC) to primarily ‘limbic’ input to the ventral mPFC (PL and IL). The AGm and dorsal AC receive afferent projections from widespread areas of the cortex (and associated thalamic nuclei) representing all sensory modalities. This information is presumably integrated at, and utilized by, the dorsal mPFC in goal directed actions. In contrast with the dorsal mPFC, the ventral mPFC receives significantly less cortical input overall and afferents from limbic as opposed to sensorimotor regions of cortex. The main sources of afferent projections to PL/IL are from the orbitomedial prefrontal, agranular insular, perirhinal and entorhinal cortices, the hippocampus, the claustrum, the medial basal forebrain, the basal nuclei of amygdala, the midline thalamus and monoaminergic nuclei of the brainstem. With a few exceptions, there are few projections from the hypothalamus to the dorsal or ventral mPFC. Accordingly, subcortical limbic information mainly reaches the mPFC via the midline thalamus and basal nuclei of amygdala. As discussed herein, based on patterns of afferent (as well as efferent) projections, PL is positioned to serve a direct role in cognitive functions homologous to dorsolateral PFC of primates, whereas IL appears to represent a visceromotor center homologous to the orbitomedial PFC of primates.     

Central stress-integrative circuits: forebrain glutamatergic and GABAergic projections to the dorsomedial hypothalamus,medial preoptic area,and bed nucleus of the stria terminalis

Central regulation of hypothalamo-pituitary-adrenocortical (HPA) axis stress responses is mediated by a relatively circumscribed group of projections to the paraventricular hypothalamus (PVN). The dorsomedial hypothalamus (DMH), medial preoptic area (mPOA), and bed nucleus of the stria terminalis (BST) provide direct, predominantly inhibitory, innervation of the PVN. These PVN-projecting neurons are controlled by descending information from limbic forebrain structures, including the prefrontal cortex, amygdala, hippocampus, and septum. The neurochemical phenotype of limbic circuits targeting PVN relays has not been systematically analyzed. The current study combined retrograde tracing and immunohistochemistry/in situ hybridization to identify the specific sites of glutamatergic and GABAergic inputs to the DMH, mPOA, and BST. Following Fluoro-gold (FG) injections in the DMH, retrogradely labeled cells co-localized with vesicular glutamate transporter mRNA in the prefrontal cortex, ventral hippocampus, and paraventricular thalamus. Co-localization of FG and glutamic acid decarboxylase mRNA was present throughout the central and medial amygdaloid nuclei and septal area. In addition, the mPOA received predominantly GABAergic input from the septum, amygdala, and BST. The BST received glutamatergic projections from the hippocampus and basomedial amygdala, whereas, GABAergic inputs arose from central and medial amygdaloid nuclei. Thus, discrete sets of neurons in the hypothalamus and BST are positioned to summate limbic inputs into PVN regulation and may play a role in HPA dysfunction and stress-related illness.     

大鼠脑干到前额叶皮质的传入投射——WGA-HRP法研究

用WGA-HRP法研究了25只大鼠前额叶皮质的脑干传入投射。在前扣带回背部、前边缘区及岛叶无颗粒皮质背部注射WGA-HRP后,脑干中的逆行标记细胞大致可分为三类。第一类为单胺类神经元集中的核团,其中蓝斑、腹侧被盖区、黑质致密部、中缝背核、中央上核及尾侧线形核等广泛投射到前额叶皮质各部,而外侧网状核、连合核、中缝大核、A_4、A_5、臂旁核、黑质网状部及颅侧线形核投射到前额叶皮质各部的数量不同。外侧网状核、连合核、中缝大核、A_4、A_5到前额叶皮质的投射文献上尚未见报道。第二类为与眼肌运动有关的核团,如E-W核、导水管周灰质、中脑网状结构及脑桥吻侧网状核。第三类为与感觉有关的核团,如臂旁核、三叉神经感觉主核及连合核。     

Effects of antipyretics on normothermic rabbits.

The effects of antipyretics on the ear skin and rectal temperature (Te and Tre) were investigated in non-febrile rabbits placed in a cold environment or when they were cooled locally in the hypothalamus. Intravenous injections of sulpyrin (25-500 mg/kg) or sodium salicylate (25-100 mg/kg) produced the dose-related increase in Te and slight fall in Tre. Decrease in Te induced by hypothalamic cooling was also reversed by the intravenous injection of antipyretics. Intraventricular injections of sulpyrin and salicylate (0.5-5.0 mg/kg) also caused the vasodilatation of the pinna skin and the fall in Tre. Bilateral microinjections of sulpyrin were made into various areas of the brain stem in order to locate the site of action. The injection sites where the vasodilatatory effect was elicited were the anterior hypothalamus, ventromedial nucleus of hypothalamus and the midbrain reticular formation. The responses elicited from the ventromedial nucleus were usually accompanied by restless and violent struggling. Injection of antipyretics into the mammillary body had no effect on Te. Intrahypothalamic injection of procaine depressed the sulpyrin-induced vasodilatation. These findings suggest that action of antipyretics on the normal body temperature is mediated through anterior hypothalamus and midbrain reticular formation.