Occurrence of vasoactive intestinal polypeptide (VIP)-like immunoreactivity in certain cholinergic neurons of the cat: evidence from combined immunohistochemistry and acetylcholinesterase staining

RU38486 blocks the steroid regulation of transmitter choice in cultured rat sympathetic ganglia

Sympathetic neurones grown in tissue culture change phenotype from adrenergic to cholinergic due to a factor released by non-neuronal cells. Glucocorticosteroids prevent the production of this factor by non-neuronal cells and hence prevent the change in phenotype. Conventional steroid antagonists, however, fail to block this effect. We report here that the steroid antagonist RU38486 is effective in preventing the action of corticosterone on cultured sympathetic ganglia and hence may be a useful in vivo tool to study the steroid regulation of development.

Morphology of striatal neurons containing VIP-like immunoreactivity

We have used light and electron microscopic immunocytochemical techniques to study the distribution and morphology of neurons that contain vasoactive intestinal polypeptide-like immunoreactivity (VIP-Ir) in the adult rat striatum. VIP-Ir cells were sparsely distributed throughout all rostrocaudal levels of the striatum. Cell bodies were of medium size (12-17 microns) and gave rise to three to five primary dendrites, which branched close to the soma and became varicose. These dendrites appeared aspiny at the light microscope level and could be traced up to 250 microns in length. Dendrites frequently traversed axonal bundles in the striatum, a pattern not exhibited by neurons containing somatostatin-like or substance P-like immunoreactivity. In several instances, very fine varicose processes arborized extensively within 40 microns of the VIP-Ir soma; these may represent axons. In thin-sectioned preparations, examined under the electron microscope, the nucleus of VIP-Ir neurons was eccentrically located and showed several deep invaginations. Immunoreactive dendrites of VIP-Ir cells appeared virtually spine-free. Synapses with asymmetric or symmetric junctional specializations were present on the dendritic surface. Several VIP-Ir varicosities were found to terminate on the VIP-Ir cell body, forming synaptic junctions with symmetric specializations; these synapses may derive from recurrent collaterals. VIP-Ir cells thus resemble other aspiny striatal neurons considered likely to be local circuit neurons.

A subpopulation of preganglionic parasympathetic neurons in the rat contain adenosine deaminase

Immunohistochemical staining and retrograde fluorescent tracing techniques were used to demonstrate the presence of adenosine deaminase in preganglionic parasympathetic neurons. Both brainstem and sacral spinal cord parasympathetic nuclei were found to contain a subpopulation of neurons immunoreactive for adenosine deaminase. Immunostaining of preganglionic neurons in brainstem was restricted to a group of cells which were shown by retrograde tracing with Fast Blue to project exclusively to the sphenopalatine ganglion. This group was defined as the lacrimo-nasopalatine parasympathetic nucleus. Neurons in all other cranial preganglionic centers were devoid of adenosine deaminase immunoreactivity. In spinal cord adenosine deaminase-immunoreactive neurons were found in the intermediolateral gray matter in the region of the sacral parasympathetic nucleus. Injections of Fast Blue into the pelvic ganglion labeled large numbers of neurons in this nucleus, only some of which contained adenosine deaminase. The majority of neurons immunoreactive for adenosine deaminase were also shown to be immunoreactive for choline acetyltransferase in both brainstem and sacral parasympathetic nuclei. The present results show that a subclass of preganglionic parasympathetic neurons are among the few structures in the central nervous system that express what appear to be high levels of adenosine deaminase. This observation together with evidence suggesting that purines serve as neurotransmitters in some sacral parasympathetic neurons supports the notion that adenosine deaminase may constitute a marker for adenine nucleoside and/or nucleotide neurotransmission.

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.

Vasoactive intestinal polypeptide facilitates the late component of the 5-hydroxytryptamine-induced discharge in the cat superior cervical ganglion

The intra-arterial administration of vasoactive intestinal polypeptide (VIP, 1-10 micrograms, i.a.) to the cat superior cervical ganglion facilitated or unmasked the late component but not the early component of the 5-hydroxytryptamine (5-HT, 0.5-50 micrograms, i.a.)-induced postganglionic discharge. The facilitation occurred in acutely and chronically decentralized ganglia. The early and late 5-HT discharges were blocked by MDL-72222, a 5-HT antagonist, but not by cholinergic antagonists. These data together with previous observations indicate that VIP selectively facilitates slow cholinergic and non-cholinergic excitatory mechanisms in autonomic ganglia.

Comparison of the vasodilatory effects of vasoactive intestinal polypeptide (VIP) and peptide-HI (PHI) in the rabbit and the cat

In rabbits, intravenous infusion of increasing doses of peptide-HI (PHI), with direct measurement of the uveal blood flow from a cannulated vortex vein, caused a dose-dependent decrease in the uveal vascular resistance. The maximal effect, a 50% decrease, was achieved with about 60 pmol kg-1 min-1. This is similar to what has previously been reported for vasoactive intestinal polypeptide (VIP). Determination of local blood flows, with radioactive microspheres, showed that i.v. infusion of VIP or PHI (60 pmol kg-1 min-1) caused about the same increase in the choroidal blood flow, while the local blood flow in the anterior uvea was unaffected by both peptides. The most marked effect of VIP was observed in glandular tissues, such as the pancreas, submandibular, parotid and thyroid glands. The pancreas was the only one of these tissues in which PHI caused an increased blood flow. In cats, i.v. infusion of VIP (30 pmol kg-1 min-1) during 5-7 min caused a markedly increased blood flow in several tissues. The vasodilation in glandular tissues was even more marked than in rabbits; 3-15 times the normal compared with two to five times the normal in rabbits. The choroidal blood flow was however significantly decreased and the local flow in the anterior uvea tended also to be reduced. Intravenous infusion of either a higher dose of VIP (60 pmol kg-1 min-1) or of PHI (1800 pmol kg-1 min-1) during 2 min had no effect on the uveal vascular resistance. This dose of PHI had only minor effects on local blood flows in other tissues. The results of the present study indicate that porcine VIP is a more potent vasodilator than porcine PHI in most tissues of both the cat and the rabbit, but that there may be exceptions such as the rabbit uvea. The difference in potency may also vary considerably between the species.

Autonomic innervation of the arteriovenous anastomoses in the dog tongue. A histochemical and ultrastructural study

The innervation of the arteriovenous anastomoses in the dog tongue has been investigated. At the light-microscopic level, the vessels were found to be densely supplied with adrenergic and AChE-positive nerve plexuses and less densely with the quinacrine-binding nerve plexus. At the electron-microscopic level, at least two apparently different types of axon profiles were identified: Small vesicle-containing axons, characterized by many small granular vesicles, variable numbers of small clear vesicles and large granular vesicles. Storage of endogenous amines and uptake of exogenous amines into most small granular vesicles and many large granular vesicles was demonstrated. These axons stained only lightly with reaction products for AChE activity and thus seemed to be adrenergic in nature. Some axons contained numerous large granular vesicles, whose cores occasionally stained with uranyl ions; this suggests a co-localization of ATP or peptides as neurotransmitters. Small granular vesicle-free axons, containing small clear vesicles and large granular vesicles in variable ratio. Most cores of these large granular vesicles were heavily stained with uranyl ions. No storage or uptake of amine into the synaptic vesicles was detected. Some axons appeared to be typically cholinergic, some, typically non-adrenergic, non-cholinergic, and the rest, intermediate between the two. All axons stained heavily with reaction products for AChE activity, suggesting their cholinergic nature.

Peptide-containing nerve fibres in human extracranial tissue: a morphological basis for neuropeptide involvement in extracranial pain?

It has been suggested that a number of peptides may be involved in the transmission of pain. In order to evaluate the possible role of peptides in the development of headache, we have, in the present study, examined the presence of nerve fibres containing neuropeptide Y (NPY), vasoactive intestinal peptide (VIP), substance P (SP) and calcitonin gene-related peptide (CGRP) in human temporal and occipital tissues. In the skin, delicate VIP, SP and CGRP fibres occur beneath the epidermis, sometimes running into the folds of the dermal ridges. In deeper layers of the dermis, small blood vessels are occasionally surrounded by single nerve fibres containing NPY, VIP, SP and CGRP. Large temporal and occipital arteries are surrounded by a meshwork of such fibres. In addition, NPY and VIP fibres are seen around sweat glands and hair follicles. Smooth muscle bundles in the dermis are surrounded by VIP fibres, whereas the temporal muscle per se is devoid of such fibres.

In vitro evidence that vasoactive intestinal peptide is a transmitter of neuro-vasodilation in the head of the cat

Experiments have been undertaken to determine the nature of the atropine-resistant neurogenic dilation that can be demonstrated in vitro in cephalic arteries of the cat. Levels of vasoactive intestinal peptide (VIP) and substance P were measured in a number of arteries and related to the extent of the neurogenic dilation that can be elicited in vitro. There is no correlation between the tissue contents of the two peptides. A positive correlation was found between vasoactive intestinal peptide but not substance P content and neurogenic dilation. Vasoactive intestinal peptide but not substance P consistently caused a concentration-dependent dilation of cephalic arteries not subject to significant tachyphylaxis. Vasoactive intestinal peptide antiserum in concentrations that block the dilation to vasoactive intestinal peptide (10(-6) M) but not that due to papaverine, significantly reduced neurodilation of both atropinized and non-atropinized lingual arteries--the cephalic artery with the highest VIP content. These results suggest that vasoactive intestinal peptide and not substance P significantly contributes to the non-cholinergic neurogenic dilation observed in vitro in arterial segments from the head of the cat.

A detailed account of NPY-immunoreactive nerves and cells of the human skin. Comparison with VIP-, substance P- and PHI-containing structures

Neuropeptide Y (NPY)-like immunoreactivity has been found in autonomic nerve terminals and fibres of the normal human dermis by the use of indirect immunohistochemistry. Also a granular immunoreactivity was observed in the basal cells of the epidermis as well as in the cells of the outer root sheath of hair follicles. Thus, NPY should be considered when examining the role of different autonomic neurotransmitter candidates. Furthermore, NPY and norepinephrine may, at this level, serve together as co-transmitters or co-modulators of autonomic function. Finally, the immunoreactivity found in cells of the epidermis and the outer root sheath of hair follicles points to other functional effects so far not understood.

Occurrence, distribution and ontogeny of CGRP immunoreactivity in the rat lower respiratory tract: effect of capsaicin treatment and surgical denervations

The occurrence and distribution of calcitonin gene-related peptide (CGRP) immunoreactivity in the rat respiratory tract were investigated by means of immunocytochemistry and radioimmunoassay using antibodies raised in rabbits to synthetic rat CGRP. Substantial amounts of CGRP immunoreactivity (range 5-37 pmol/g) were detected in all parts of the respiratory tract, the highest being in the stem bronchus. Gel filtration chromatography of extractable CGRP immunoreactivity revealed one single peak, eluting at the position of synthetic rat CGRP. CGRP immunoreactivity was localized both in mucosal endocrine cells and nerve fibres from the larynx down to the peripheral lung. CGRP-immunoreactive endocrine cells were found singly in trachea and stem bronchi and in groups in intrapulmonary airways. They appeared at a late stage of gestation (17 days), reached a maximum number near term and decreased after birth to maintain a population similar to that of the adult animals by postnatal day 21. Similarly, CGRP-immunoreactive nerve fibres were first identified by day 18 of the gestation period and reached the adult distribution by postnatal day 21. CGRP-immunoreactive nerve fibres were localized among smooth muscle, seromucous glands, beneath and within the epithelium of the airways and around blood vessels. CGRP was also found in sensory ganglia and in motor end plates of the larynx musculature. Neonatal pretreatment with capsaicin caused a marked reduction in CGRP immunoreactivity of nerve fibres in the respiratory tracts as well as a less marked decrease in the population of CGRP-containing endocrine cells of the lung. No change was seen in motor end plates immunostaining. Vagal ligation experiments revealed that CGRP-immunoreactive nerve fibres travelling in the vagus originate mainly from neurons located in the jugular ganglion. Infranodosal right vagal ligation induced a marked loss in CGRP-immunoreactive nerves of the trachea, and of the ipsilateral stem bronchus, but no changes were observed in peripheral lung. By contrast infranodosal left side vagal ligation caused a decrease in CGRP-immunoreactive nerves of the ipsilateral lung and bronchus without affecting the peptide content in the trachea. Left vagal ligation also induced a marked increase in both the intensity of staining and number of CGRP-immunoreactive endocrine cells in the lung. We conclude that CGRP immunoreactivity is localized in both nerve fibres and endocrine cells and is associated principally with the afferent (sensory) innervation of the respiratory tract.(ABSTRACT TRUNCATED AT 400 WORDS)

Conditions increasing the adrenergic properties of dissociated chick superior cervical ganglion neurons grown in long-term culture

Neurons dissociated from the embryonic chick superior cervical ganglion (SCG) were separated from ganglionic nonneuronal cells using a density gradient formed with Percoll. The sympathetic neurons were then grown for 3-4 weeks in serum containing medium on a polyornithine substrate precoated with heart-conditioned medium. Both catecholamine (CA) and acetylcholine (ACh) are synthesized and accumulated by these neurons, but the amount of CA is higher and increases much more over time in culture than the amount of ACh. The cultures become therefore more adrenergic with time. We report here that the adrenergic properties of these cells can be enhanced. A 3-fold increase in CA synthesis, as expressed on a per neuron basis, is obtained by increasing neuron cell density 3- to 4-fold. ACh synthesis, however, is decreased at high neuronal density. Optimal CA production is obtained at densities of 120-150,000 neurons/cm2. This effect is due to direct cell contact since it cannot be transferred to low density cultures by medium conditioned by high density cultures. Nerve growth factor concentrations 5-10-fold higher than the amount necessary for optimal neuronal survival (1 microgram/ml 7S NGF) increases CA production but do not affect ACh synthesis. This effect is highest at low plating densities (20-30,000 neurons/cm2, 10-fold increase) and progressively decreases with increasing neuronal density. No increase is obtained in high density cultures where CA production is maximal. In addition, we made the novel observation that medium conditioned by chick liver cells in culture (LCM) increases CA production approximately 4-fold, whereas it does not increase ACh production by the SCG neurons. Work is in progress to biochemically characterize the active component(s) present in the LCM and to determine whether they favor the survival of a subpopulation of adrenergic neurons possible present in these ganglia. Alternatively, the adrenergic differentiation of neurons initially capable of synthesizing both CA and ACh could be selectively increased by LCM.

Some properties of adenosine 3',5'-cyclic monophosphate phosphodiesterase in the superior cervical ganglion of the guinea pig

Adenosine 3',5'-cyclic monophosphate (cAMP) phosphodiesterase activity in crude guinea-pig superior cervical ganglion homogenates was assayed under a variety of experimental conditions. Two forms of cAMP phosphodiesterase were found, one with high and the other with low affinity for the substrate. The Km values were about 1 and 110 microM respectively. Imidazole slightly but constantly stimulated the former enzyme form over a wide range of concentrations and 1-methyl-3-isobutylxanthine was a weak competitive inhibitor with a Ki value of 90 microM. Low affinity cAMP phosphodiesterase activity was increased by calmodulin and Ca2+. This stimulation was not observed in the presence of trifluoperazine, a specific inhibitor of calmodulin. On the other hand, neither [D-Ala2]met-enkephalinamide nor prostaglandin E2, alone or in combination, influenced high affinity cAMP phosphodiesterase.

The contribution of cholinergic enzymes and acetylcholine from the lumbar sympathetic chain to the rat sciatic nerve

This study was performed to investigate how much of the acetylcholine (ACh), choline acetyltransferase (ChAT) and ACh-esterase (AChE) in the rat sciatic nerve originate from the somatic motor input and from the automatic sympathetic input, respectively. The somatic motor axons to the sciatic nerve were eliminated by surgical transsection of the spinal roots, (rhizotomy) and the autonomic component was removed by surgical resection of the lumbar sympathetic chain bilaterally (sympathectomy). Also combined operations were performed. In intact (non-crushed) sciatic nerve rhizotomy caused a reduction in ACh content by 70%, in ChAT-activity by 55%, and in AChE-activity by 41%. Sympathectomy alone had very little influence on ACh and ChAT, but reduced AChE by 20%. After crushing the nerve 13 hours before sacrifice, all three substances accumulated proximal to the crush region as described previously. When compared to the control group, sympathectomy alone caused a reduction in accumulated amounts of AChE only, while ACh and ChAT accumulations were essentially unchanged. Rhizotomy alone caused a substantial reduction in accumulated amounts of all three substances, but most prominently in ACh and ChAT-amounts. After sympathectomy in combination with rhizotomy ACh-accumulations were very low, and enzyme activities were reduced more than in the group with rhizotomy alone. A certain amount of residual ChAT and AChE was present in the nerve, and the location of this is discussed. The fact that combined sympathectomy and rhizotomy lowered ACh accumulations significantly more than would be expected from the results after either operation alone is commented upon.

Pineal indoles: significance and measurement

Despite intensive investigation, particularly over the past fifteen years, many aspects of pineal function with respect to mammalian physiology remain obscure. Much of this work is reviewed and particular attention focussed on indole metabolism within the pineal gland. Emphasis is placed on the development of new analytical techniques with special reference to high performance liquid chromatography coupled with electrochemical detection. The growth in knowledge regarding pineal indole synthesis which can be attributed to the use of this technique is discussed. The possibility that pineal indoles other than melatonin may function as hormones or neuromodulators is considered. A functional role for 5-hydroxytryptophol as a neuromodulator, possibly associated with diffuse neuroendocrine function (amine precursor, uptake and decarboxylation, APUD) is suggested.

Localization of choline acetyltransferase and vasoactive intestinal polypeptide-like immunoreactivity in the nervus terminalis of the fetal and neonatal rat

Ganglia of the nervus terminalis have been shown to contain luteinizing hormone-releasing hormone (LHRH) immunoreactive cells in several mammalian species. These cells are always accompanied by clusters of cells non-immunoreactive to antiserum to LHRH. Using immunocytochemical procedures, we found choline acetyltransferase (ChAT) and vasoactive intestinal polypeptide (VIP) present in cell bodies and in nerve processes throughout the peripheral, intracranial and central projections of the nervus terminalis. In addition, a dense plexus of substance P (SP) immunoreactive fibers was seen in the nasal mucosa surrounding the nasal glandular acini and blood vessels. A number of SP reactive fibers were traced with the olfactory nerves through the cribriform plate of the ethmoid bone and appeared to enter the brain in the area of the central roots of the nervus terminalis.

Pathway of acetylcholinesterase containing nerves to the major cerebral arteries in rats

The pathway of nerves containing acetylcholinesterase (AChE) to the major cerebral arteries was investigated in the rat. In this species, the internal ethmoidal artery (IEA) arises from the anterior cerebral artery (ACA) and anastomoses with the external ethmoidal artery (EEA), forming the ethmoidal rete on the cribriform plate. The ethmoidal nerve (EN) and EEA enter the cranial cavity through the ethmoidal foramen. Densely distributed adventitial nerve plexi were present around the IEA, ethmoidal rete, and EEA. Many thick nerve bundles were found in the periadventitial layers in association with these vessels. Around the EN, just before it enters the ethmoid foramen, intensely staining nerve bundles were present that entered the cranial cavity with the EN. After unilateral section of the EN and EEA, a marked decrease of the nerve fibers was observed around the arteries of the anterior part of the circle of Willis on the operated side, whereas the basilar artery (BA) showed a moderate decrease in the AChE activity. After bilateral section of the EN and EEA, nerves disappeared from around all the major cerebral vessels including the BA. Section of the EEA alone did not produce any visible change of the cerebral perivascular innervation. The present study suggests that AChE-containing nerves on the cerebral arteries arise from the AChE-positive nerve bundles, which enter the cranial cavity with the EN through the ethmoid foramen; The anterior part of the circle of Willis is innervated unilaterally by the AChE-positive nerve bundles from the ethmoidal foramen, whereas the BA receives bilateral innervation.

Neurotransmitters in the cerebral cortex

This article surveys the conventional neurotransmitters and modulatory neuropeptides that are found in the cerebral cortex and attempts to place them into the perspective of both intracortical circuitry and cortical disease. The distribution of these substances is related, where possible, to particular types of cortical neuron or to afferent or efferent fibers. Their physiological actions, where known, on cortical neurons are surveyed, and their potential roles in disease states such as the dementias, epilepsy, and stroke are assessed. Conventional transmitters that occur in afferent fibers to the cortex from brain-stem and basal forebrain sites are: serotonin, noradrenaline, dopamine, and acetylcholine. All of these except dopamine are distributed to all cortical areas: dopamine is distributed to frontal and cingulate areas only. The transmitter in thalamic afferent systems is unknown. Gamma aminobutyric acid (GABA) is the transmitter used by the majority of cortical interneurons and has a profound effect upon the shaping of receptive field properties. The vast majority of the known cortical peptides are found in GABAergic neurons, and the possibility exists that they may act as trophic substances for other neurons. Levels of certain neuropeptides decline in cases of dementia of cortical origin. Acetylcholine is the only other known transmitter of cortical neurons. It, too, is contained in neurons that also contain a neuropeptide. The transmitter(s) used by excitatory cortical interneurons and by the efferent pyramidal cells is unknown, but it may be glutamate or aspartate. It is possible that excitotoxins released in anoxic disease of the cortex may produce damage by acting on receptors for these or related transmitter agents.

Coexistence of calcitonin gene-related peptide and vasoactive intestinal peptide in cholinergic sympathetic innervation of rat sweat glands

Immunoreactivity for calcitonin gene-related peptide (CGRP) has been localized with indirect immunofluorescence techniques in the cholinergic sympathetic fibers that innervate eccrine sweat glands in the rat. This innervation also contains vasoactive intestinal peptide-like immunoreactivity (VIP-IR). A small proportion of principal neurons in stellate and lumbar sympathetic ganglia which provide innervation to the sweat glands contain detectable CGRP-immunoreactivity. The CGRP-IR neurons are immunoreactive for VIP; however, many VIP-IR neurons in these ganglia do not contain detectable levels of CGRP-IR.

Histochemical demonstration of a concomitant reduction in neural vasoactive intestinal polypeptide, acetylcholinesterase, and noradrenaline of cat uterus during pregnancy

Noradrenaline, acetylcholinesterase, and vasoactive intestinal polypeptide (VIP) were visualized in uterine nerves of cats by histochemical techniques. Alterations were followed in different regions of the organs at various stages of pregnancy and compared with the situation in non-pregnant controls. Positively stained nerve fibres, the adrenergic type being particularly well developed, were found along the muscle bundles and around blood vessels in the smooth muscle layers, as well as in the mucosa, of both uterine horns and cervix. The nerve supply was especially prominent in the upper part of the cervix. The distribution of VIP-immunoreactive and acetylcholinesterase-positive nerve fibres resembled each other, but they were less numerous than the adrenergic fibres. In the course of pregnancy there was a marked reduction in the number of all positively reacting nerves, so that almost no fibres were visible in the uterine horns near term. A small number of positive nerve fibres was found to remain, however, in the wall of the sterile (empty) horn during unilateral pregnancy. The reduction was less prominent in the cervix, particularly its lower part. Distinct changes were encountered already during early and mid pregnancy in those parts of the uterine wall distended by the growing conceptus, where almost no fibres were seen. The nerve supply was more intact in the non-distended portions located between the fetuses, and especially in the empty horn of unilateral pregnancy. No overt reduction in the number of positively stained nerve fibres was found in the cervix at these pregnancy stages. The results show that marked alterations take place in the uterine autonomic innervation during such an entirely physiological event as pregnancy. There is reason to assume that the histochemical observations reflect both structural and functional alterations in the innervation related both to the type of nerves involved and to the localization of the conceptus.

Vasoactive intestinal polypeptide depolarizations in cat bladder parasympathetic ganglia

The effect of vasoactive intestinal polypeptide (VIP) on the neuronal membranes of isolated cat vesical pelvic ganglia and its underlying ionic mechanism were examined by means of intracellular recording and voltage-clamp techniques. Application of VIP (0.05-50 microM) to the neurones by pressure 'puff' ejection through a micropipette placed close to the neurones produced a depolarizing response (2-15 mV) in 83% of neurones tested; this effect was concentration dependent. The VIP-induced depolarization frequently evoked spontaneous action potentials in quiescent neurones and increased the frequency of action potentials in spontaneously firing neurones. The VIP depolarization was not blocked in a Ca2+-free, high-Mg2+ solution or in a solution containing hexamethonium (1 mM) and atropine (1 microM). Tetrodotoxin (TTX; 1 microM) also did not affect the VIP depolarization. The VIP depolarization was associated with an increase in membrane resistance and the slope of a current-voltage relation (I-V curve) was increased by VIP. Conditioning hyperpolarization and depolarization of the membrane increased and decreased the amplitude of the VIP depolarization, respectively. The VIP depolarization reversed polarity around--100 mV. The reversal potential shifted about 20 mV to a more positive level in a high-K+ (10 mM) solution in accord with the Nernst equation. Substituting Cl- with isethionate in the superfusate did not affect the reversal potential of the VIP depolarization. Closure of M-channels does not underlie VIP action since the VIP depolarization was enhanced by muscarine (10 microM) and unchanged in the presence of Ba (5 mM), or intracellular or extracellular Cs+, conditions known to block the M-channels (Adams, Brown & Constanti, 1982a, b). Tetraethylammonium (TEA; 20 mM) also did not affect the VIP depolarization. Voltage-clamp analyses showed that VIP applied by pressure ejection produced an inward current of 80-110 pA associated with a decrease in membrane conductance (from 2.8 to 3.5 nS) at a holding potential of--60 mV. VIP inward current was diminished by either repetitive or continuous application of VIP (5 microM) suggesting desensitization of the VIP receptor. It is concluded that VIP produces a depolarization in neurones of bladder parasympathetic ganglia by decreasing a K+ conductance, the pharmacological characteristics of which are unlike previously described K+ conductance mechanisms.

Cerebrovascular projections from the sphenopalatine and otic ganglia to the middle cerebral artery of the cat

The location of the postganglionic parasympathetic cell bodies projecting to cerebral arteries is unknown. Using axonal tracing techniques, we examined whether the sphenopalatine ganglia (associated with the seventh cranial nerve) and otic ganglia (associated with ninth cranial nerve) contain perikarya which send axons to the feline middle cerebral artery (MCA). The tracers horseradish peroxidase (HRP: 3 cats) or wheat germ agglutinin (WGA: 6 cats) were applied to the MCA in a slow release polymeric system. Three days later the SPG, otic ganglia, and rete mirabile were harvested bilaterally and processed for tracer by the TMB method (HRP) or immunohistochemistry (WGA). In a given animal, approximately equal numbers of cells containing axonal tracer were found in both SPG. Labeled fibers occasionally could be seen extending into the vidian nerve. Positive cells were also found in the otic ganglia and in the walls of the internal rete mirabile. These results provide the first identification of parasympathetic cell bodies projecting to cerebral blood vessels.