Cutaneous lesions in capsaicin-pretreated rats. A trophic role of capsaicin-sensitive afferents?

1. The time course and regional distribution of 'spontaneous' cutaneous lesions in rats desensitized to capsaicin as newborns was correlated to behavioural observations and regional distribution of substance P-like immunoreactivity (SP-LI) and tachykinin-like immunoreactivity (TK-LI) in various skin areas. 2. 'Spontaneous' skin lesions in the form of wounds, scabs and areas of alopecia were observed in 80-90% of rats desensitized to capsaicin. No major sex-related differences were observed with regard to incidence and distribution of the lesions with the possible exception of a lesser tendency to bilateral lesions in female rats. 3. 'Spontaneous' skin lesions were almost restricted to the head: the areas most frequently affected were snouts, periocular and retroauricular regions and ventral area of the neck. 4. No major differences were observed between capsaicin- or vehicle-treated animals in spontaneous or novelty-induced grooming as well as in open-field gross behaviour. Likewise, no differences were observed in the mouse-killing behaviour. 5. Both SP-LI and TK-LI in various skin areas were significantly reduced by systemic capsaicin pretreatment. The rank order of various skin areas for SP-LI or TK-LI levels was: snouts greater than thigh greater than neck greater than abdomen approximately equal to retroauricular region. 6. Intradermal injection of Arg-neurokinin B, a potent and water soluble derivative of neurokinin B, produced a similar plasma extravasation (Evans blue leakage technique) in the skin of vehicle- or capsaicin-pretreated rats. 7. In capsaicin-desensitized rats fur regrowth (measured at abdominal level, 28 days after shaving) was significantly less than in vehicle-treated animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Enzyme histochemistry of the choroid plexus in old rats

The influence of ageing on the metabolic profile of lateral ventricle choroid plexus epithelial cells from young (3-month-old) and aged (26-month-old) male Wistar rats was studied using enzyme histochemical techniques. The following enzymatic activities related to energy transduction were examined: lactate-(LDH) and succinate- (SDH) dehydrogenases; NADH2-tetrazolium reductase (NADHD) and alpha-glycerophosphate-dehydrogenase (GPDH). The intensity of enzymatic staining within single choroid plexus epithelial cells from young and old animals was assessed microphotometrically. In the choroid plexus epithelial cells of young rats NADHD was the enzymatic activity more heavily stained; cell levels of LHD and GPDH were approximately the same and SDH reactivity was less intense. In old age LDH was reduced by 9.3%, SDH was reduced by 26.1%, NADHD was reduced by 8.6% and GPDH was reduced by 3.6%. The possibility that impaired energy transduction mechanisms at the level of choroid plexus epithelium in old age may influence functional activity of the choroid plexus is discussed.

Autoradiographic localization of the GABAA receptor agonist [3H]muscimol in rat cerebral vessels

By the use of combined in vitro radioreceptor binding and autoradiographic techniques with [3H]muscimol as a ligand, we analyzed the distribution of GABAA receptor sites in the arteries of the circle of Willis as well as in the arteries and arterioles of the pial-arachnoid membrane in the rat. [3H]Muscimol was bound by sections of rat cerebral vessels in a manner consistent with the existence of GABAA receptors, with Kd and Bmax values of 46 nM and 0.60 pmol/mg tissue respectively. [3H]Muscimol was bound by the medial layer of cerebral arteries, while no specific binding was observed in the intima, the adventitia and the adventitial-medial border. These findings suggest that the vasodilatory action of GABA on in vitro preparations of cerebral vessels is mediated by muscular receptor sites. The posterior cerebral arteries are richer in [3H]muscimol binding sites than the anterior ones. Pial-arachnoid arterioles, which are of critical importance in controlling local cerebral blood flow, did not exhibit any significant binding of [3H]muscimol. These results may explain the difficulty in manipulating pharmacologically the cerebral tissue perfusion in intact animals using GABAergic agonists.

Substance P-like immunoreactivity in capsaicin-sensitive structures of the rat thymus

Unlike in mouse and hamster, the thymus of rats or guinea pigs contains measurable amounts of substance P-like immunoreactivity (SP-LI), which, in a HPLC system, eluted as authentic SP or SP sulfoxide. Ontogenetic study showed that in rats the SP-LI content of the thymus increased up to 60 days from birth, and decreased thereafter. Capsaicin, but not 6-hydroxydopamine (6-OHDA) pretreatment completely depleted thymic SP-LI content in both newborn and adult rats. Animals treated with capsaicin as newborns, but not as adults, showed lower thymus weights as compared to controls. Rats pretreated with capsaicin as adults underwent partial time-dependent recovery of thymic SP-LI content. Somatostatin-like immunoreactivity (SST-LI) of rat thymus, eluting in part as authentic SST, was unaffected both by capsaicin or 6-OHDA pretreatment. Taken together, these findings demonstrate the existence of capsaicin-sensitive structures containing SP in the rat thymus. The possible function(s) that capsaicin-sensitive structures could exert in the thymus, among which a trophic action, mediated by the efferent function of sensory neurons, remain(s) to be established.

Metabolism of coronary vasculature in senescent rats--a histochemical study

The effect of senescence on the metabolic profile of rat coronary arteries and arterioles was studied using enzyme histochemical techniques. In coronary arteries anaerobic metabolism predominates. In senescence an increase of adenosine triphosphatase (ATPase) occurred. The succinate dehydrogenase (SDH) and the respiratory chain metabolism marker NADH2-tetrazolium reductase (NADHD) showed an age-related decrease. Lactate dehydrogenase was unchanged. In the coronary arterioles, on the contrary, aerobic metabolism dominates. In senescence a significant decrease of NADHD and a moderate reduction of SDH and ATPase was observed. L-Carnitine administration significantly stimulated some enzymatic activities related to aerobic metabolism primarily at the arteriolar level.

Dopamine receptors mediating the stimulation and the inhibition of adenylate cyclase in rat prostate gland

The effect of dopamine on the 3',5'-cyclic adenosine monophosphate (cAMP) generating system of membrane particles of rat prostate gland was studied. Dopamine increased the concentration of cAMP in a dose-dependent manner. The selective D1 receptor inhibitor SCH 23390 caused a decrease in dopamine-elicited cAMP levels. Any effect of dopamine on prostatic cAMP concentration was abolished by the simultaneous addition to the incubation medium of SCH 23390 and of the D2 receptor blocking agent (-)-sulpiride. Also the D2 receptor agonist bromocriptine decreased cAMP levels. The present data indicate the existence, in the rat prostate gland, of two types of dopamine receptors mediating, respectively, the activation (D1 effect) and the inhibition (D2 effect) of adenylate cyclase activity.

Effect of vasoactive intestinal polypeptide on the cyclic adenosine monophosphate generating system in rat kidney glomeruli and cortical tubules

The effect of in vitro addition of vasoactive intestinal polypeptide (VIP) on the 3'-5'-cyclic adenosine monophosphate (cAMP) generating system in rat kidney glomeruli and cortical tubules was studied. VIP did not stimulate cAMP accumulation in glomeruli; but VIP did stimulate, specifically and in a dose-dependent manner, cAMP concentrations in tubular membranes with the addition of GTP. These results are consistent with the existence of a functionally active VIP receptor coupled to adenylate cyclase in rat kidney cortical tubules.

Enzyme histochemistry of monoamine oxidase in the heart of aged rats

The distribution of monoamine oxidase types A and B in the heart of young (3-month-old) and aged (26-month) Wistar rats was studied by histochemical methods. In young rats, MAO activity was higher in the left ventricle than in the right. Enzyme reactivity was present within both muscle cells and the blood vessel wall. Histochemical staining was abolished by clorgyline administration. In the heart of aged rats, we observed a very remarkable increase of clorgyline sensitive MAO activity primarily at the level of myocardial cells. The right ventricle showed the highest increase of MAO reactivity.

Autoradiographic localization of the dopaminergic agonist 3H-dihydroergotoxine within the male reproductive system

By the use of combined radioreceptor binding and autoradiographic techniques, we analyzed the anatomical localization of the dopaminergic agonist 3H-dihydroergotoxine in tissue sections of rat male sex organs. The drug was bound by smooth muscle cells of the deferent duct, seminal vesicles and prostate gland as well as by the glandular tissue of seminal vesicles and prostate gland. These data allow us to hypothesize that the effect of dopaminergic agonists on male sexual function may be due, at least in part, to a direct interaction with dopamine receptors present in the reproductive organs.

Vasoactive intestinal polypeptide levels and distribution in the penis of old rats

Vasoactive intestinal polypeptide (VIP) levels and distribution were studied in the penis of young-adult (3-month-old) and old (30-month-old) Wistar rats by radioimmunoassay and immunofluorescence. No significant changes in tissue VIP concentrations or distribution occurred in the penis of old rats compared to young-adult rats. The present data indicate that the age-related impairment of male sexual function is not dependent on modifications of the VIP-ergic innervation of penile tissue.

Quantitative image analysis of the density and pattern of adrenergic innervation of blood vessels of rat spinal cord

The density and pattern of the noradrenergic innervation of the main extramedullary blood vessels of the rat spinal cord was studied using combined glyoxylic acid histofluorescence and quantitative image analysis techniques. The anterior spinal artery has a perivascular plexus of fine noradrenergic nerves rich in varicosities; the central artery has nerve fibers of various sizes; and the posterior spinal vein has a limited plexus of noradrenergic nerve fibers. The possible significance of the noradrenergic innervation of extramedullary spinal cord blood vessels is discussed.

The noradrenergic innervation of the vasa nervorum in old rats: a fluorescence histochemical study

The effect of ageing on the density and pattern of noradrenergic nerves in the perivascular nerve plexus supplying the vasa nervorum of the rat sciatic nerve was studied using combined catecholamine histofluorescence and quantitative image analysis techniques. The density of noradrenergic fibres around arteries and arterioles of the rat sciatic nerve vasa nervorum increased in the old animals. In contrast, no changes in perivascular nerve fibres supplying the veins and venules were found in the vasa nervorum of old rats. The increase in old age of noradrenergic innervation of arteries and arterioles of the vasa nervorum may be related to the pathogenesis of some peripheral nerve diseases.

Characterization and localization of high-affinity GABA uptake in slices of the rabbit oviduct

The characteristics of [3H]gamma-aminobutyric acid (GABA) uptake by slices of the rabbit oviduct were studied, and the GABA-accumulating structures were identified by histoautoradiography. A high-affinity (Km = 5 microM), sodium-dependent GABA uptake system was demonstrated which showed significant segmental variation along the oviduct with a maximal capacity (21 nmol/g tissue per h) at the fimbriated ampullary end of the organ. The uptake showed optimum values at pH 7.4 and 37 degrees C and could be influenced by changes of K+ and Ca2+ concentrations in the medium. Unlabelled GABA, ouabain and beta-alanine completely inhibited the uptake process, whereas known inhibitors of neuronal GABA uptake (L-diaminobutyric acid, nipecotic acid) produced only partial inhibition even at high doses. In autoradiographic experiments, epithelial secretory cells were predominantly labelled by [3H]GABA. These findings indicate the presence of a non-neuronal GABA uptake system in the oviductal epithelium and do not support the earlier hypothesis of GABAergic innervation in the oviduct.

Segmental distribution and gestational changes of GABA-transaminase activity in the rat oviduct

The occurrence and the localization of 4-aminobutyrate:2-oxoglutarate transaminase (GABA-transaminase) in the non-pregnant and pregnant rat oviduct were examined using biochemical and enzyme histochemical techniques. Specific GABA-transaminase activity was detected in the ampullary and isthmic portions of the oviduct as well as in the utero-tubal junction. The enzymic activity was lower in the ampullary than in the isthmic or intramural segments of the oviduct. Pregnancy induced a significant increase of GABA-transaminase activity in each portion of the oviduct. Enzyme histochemistry showed the highest GABA-transaminase reactivity at the level of the epithelial cells of the oviduct irrespective of the portion of the tube examined. A faint specific activity was demonstrated in the smooth muscle of the oviduct while the serosa did not show specific staining. Our findings indicate that: the observed increase of GABA-transaminase activity in the oviduct of the pregnant rat may be responsible for the reduced GABA levels in the oviduct during gestation; and the extraneuronal localization of GABA-transaminase activity does not seem to support the suggestion of a possible GABAergic innervation of the oviduct.

Specific, vascular localization of GABA-transaminase in the guinea pig lung

The occurrence and distribution of 4-aminobutyrate:2-oxoglutarate transaminase (GABA-T) activity were examined in the guinea pig lung using biochemical and enzymehistochemical methods. Specific GABA-T reactivity was confined primarily to the arteries and to a lesser extent to the veins. No activity could be observed in association with bronchi, alveoli and nerve fibers. Our findings indicate that the GABA-T activity in the lung is specifically located in blood vessels. This study is the first to demonstrate GABA-T activity in peripheral blood vessels.

Light- and electron-microscopic visualization of gamma-aminobutyric acid and GABA-transaminase in the oviduct of rats. Predominant occurrence in epithelium

The distribution in the rat oviduct of gamma-aminobutyric acid and its catabolic enzyme GABA-transaminase was studied by the use of immunocytochemical and enzyme-histochemical techniques. At the light-microscopic level, both GABA immunoreactivity and GABA-transaminase enzyme reactivity were found primarily in the tubal epithelium while in the muscle layers of the organ only a faint GABA and GABA-transaminase positive staining could be detected. Electron-microscopic evaluation of the GABA immunoreactivity revealed a heavy labelling of the basal bodies (kinetosomes) and a moderate staining of the cilia. These findings indicate that the role of GABA in the oviduct is not related to neurotransmission but may be related to ciliary functions.

3H-muscimol binding sites within guinea pig ovary: a histoautoradiographic study

The distribution of 3H-muscimol within guinea pig ovary was studied using combined radioreceptor binding studies and histoautoradiographic technique performed on frozen sections of ovary mounted on microscope slides. 3H-muscimol was bound by sections of ovary in a manner consistent with the existence of specific GABA receptors. The binding was reversible, saturable, of high affinity (KD was 38 +/- 6 nmol/l and Bmax was about 378 +/- 61 fmol/mg protein, and inhibited by GABA receptor interfering drugs. 3H-muscimol binding sites were found in the blood vessel wall, in the follicle and in the oocytes. The number of oocyte and follicular receptors gradually decreases during the development of ovarian follicles.

Characterization of [3H]5-hydroxytryptamine uptake within rat cerebrovascular tree

The in vitro uptake of tritiated serotonin ([3H]5HT) was studied in a preparation of rat extracerebral arteries. The uptake of [3H]5HT was time- and temperature-dependent and of high affinity; linear regression analysis gave a Km value of 6.48 X 10(-7) M for the specific uptake. Bilateral superior cervical ganglionectomy was without effect on [3H]5HT uptake while it significantly reduced the uptake of tritiated norepinephrine by the preparation of rat extracerebral arteries. The serotonergic neurotoxin 5,7-dihydroxytryptamine and lesions to both the medial and the dorsal raphe nuclei caused a marked loss of [3H]5HT uptake but did not change the uptake of tritiated norepinephrine. Competition studies with norepinephrine, desimipramine (a noradrenergic uptake blocker), nomifensine (a dopaminergic uptake blocker) and fluoxetine (a 5HT uptake blocker) confirmed the specificity of the [3H]5HT uptake mechanism. Histoautoradiographic studies showed the highest density of silver grains at the level of the adventitial-medial border of the basilar artery. Fluoxetine inhibited the accumulation of silver grains within the adventitial-medial border in the blood vessel studied. The present data further support the view that a neuronal serotonergic system may play a role in the control of blood flow in the cerebrovascular tree.

Dopamine-sensitive adenylate cyclase in rabbit portal vein

The effect of dopamine (DA) on 3',5'-cyclic adenosine monophosphate (cAMP) generation in the rabbit portal vein was investigated. Dopamine added to homogenates of rabbit portal vein increased the concentration of cAMP. DA-elicited cAMP increase was exclusively inhibited by DA antagonists fluphenazine and haloperidol suggesting the existence of DA receptors (of the DA1 subtype) in the portal vein.

The adrenergic innervation of rat uterine tubes in old age: a fluorescence histochemical study

The effect of ageing on the density and pattern of adrenergic innervation of rat uterine tubes was studied using combined glyoxylic acid induced fluorescence and quantitative image analysis techniques. With age a reduction in the number of nerve fibers of the circular muscle layer of the isthmic portion was observed. No significant differences in the density of innervation were found at the level of blood vessels associated with uterine tubes.

Stimulatory effect of neonatal beta-estradiol treatment on aspartate-aminotransferase activity within rat cerebellar cortex

The effect of neonatal beta-estradiol treatment on the Aspartate-aminotransferase (Asp-T) activity within rat cerebellar cortex has been studied using a semi-quantitative histochemical technique. The Asp-T, localized chiefly at the level of nerve fiber-like structures in the molecular layer as well as around the perikaryon of Purkinje neurons, is significantly stimulated after estrogenization. The nerve fibers localized in the molecular layer were the Asp-T cerebellar structures more remarkably influenced by beta-estradiol treatment.

Histoautoradiographic localization of (-)-3H-dihydroalprenolol in rabbit aorta

The distribution pattern of (-)-3H-dihydroalprenolol (3H-DHA) binding sites within the thoracic and abdominal aorta was studied using a histoautoradiographic technique. Frozen sections of rabbit aorta were incubated with 3H-DHA in the presence or absence of 1 mumol/l (-)-propranolol and of increasing concentrations of various adrenergic agents. After washing, the same secretions were placed in scintillation vials and counted to evaluate the pharmacological characteristics of 3H-DHA binding or processed for histoautoradiography. 3H-DHA was bound by sections of the rabbit aorta in a manner consistent with the presence of beta-adrenoceptors. The binding was reversible, saturable and of high affinity, with a dissociation constant Kd of 1.0 nmol/l and a maximum binding capacity Bmax of 17 fmol/mg tissue (wet weight). It was inhibited only by beta-adrenoceptor blocking drugs. Histoautoradiographic studies revealed that beta-adrenoceptors are located primarily in the media and then in the intima. The lowest density of 3H-DHA was found in the adventitia. The distribution pattern of beta-adrenoceptors in the media suggests the possible existence of two groups of beta-adrenoceptors within this layer of the aorta. The first group was found in the outer portions of the media and may be controlled by the adrenergic nerves that supply the artery. The second group was found in the portions of the media closest to the intima and is likely under the control of catecholamines coming from the lumen of the aorta.

Changes of [3H]spiroperidol binding in the renal artery of aged rabbits

Using mature (12 months), old (70 months) rabbits and 3H-labeled spiroperidol, the characteristics of renal artery dopamine receptors were studied. In old age the dissociation constant of [3H]spiroperidol was unchanged, while maximum specific binding was reduced more than 45%. The present data seem to indicate an impairment of peripheral dopaminergic function in ageing.

Age-associated decrease of dopamine-sensitive adenylate cyclase in rabbit renal artery

Using renal arteries from young (6 months), mature (18 months) and old (70 months) rabbits, the effect of dopamine on 3',5'-cyclic adenosine monophosphate (cAMP) generation was studied. No significant differences in basal adenylate cyclase values were found in homogenates of renal artery from young, mature or old rabbits. The protein content of the renal artery was also unchanged during the lifespan. Dopamine stimulated the production of cAMP. The stimulatory effect of dopamine was similar in the renal artery of young and mature rabbits but was lower by about 40% in old rabbits. The present results led us to hypothesize an impairment of the peripheral dopaminergic system in old age similar to that described for the central dopaminergic system.