Injection of orphanin FQ/nociceptin into the periaqueductal gray suppresses the forebrain-elicited vocalization in the guinea pig

Electrical stimulation of the caudoventral part of the anterior cingulate cortex (AC) evokes a species-specific vocalization in the guinea pig. After injections of glutamate receptor antagonists into the periaqueductal gray (PAG) regions where the AC projected, the forebrain-elicited vocalization (FEV) was suppressed completely. This result indicated that the FEV was induced at least partly by glutamatergic activation of PAG neurons. Injection of orphanin FQ/nociceptin (OFQ/N) into the PAG profoundly suppressed the FEV. This inhibitory effect of OFQ/N was not antagonized by naloxone, an opioid receptor antagonist. Since OFQ/N was reported to modify the glutamatergic transmission, the present results suggest that OFQ/N exerts influences upon the vocalization by regulating the glutamatergic inputs into the PAG.     

Immunohistochemical evidence for extrinsic and intrinsic opioid systems in the guinea pig superior cervical ganglion

Summary Immunohistochemical localization of the opioid peptides -neo-endorphin (-neo-END), dynorphin A (DYN) and leu-enkephalin (leu-ENK) in the guinea pig superior cervical ganglion (SCG) was studied following central denervation, peripheral axotomy, and after application of the depleting drug reserpine and of the neurotoxin 6-hydroxydopamine. The paraganglionic cells of the SCG are shown to form an intrinsic opioid — (-neo-END, DYN, leu-ENK) — immunoreactive system being not visibly responsive to the experimental procedures. Leu-ENK-immunoreactive fibres ascend in the preganglionic trunk and supply fibre baskets to defined clusters of postganglionic neurones. Principal ganglion cells of the SCG containing -neo-END-and DYN-immunoreactivity project to extraganglionic targets via the postganglionic nerves. These findings are indicative of a sympathetic -neo-END-ergic and DYN-ergic innervation of effector organs. They also point to a modulatory function of opioids on neuronal activity in a paravertebral ganglion.     

Age-related changes in gallbladder contractility and gallbladder cholecystokinin receptor population in the guinea pig

We have examined the effects of aging on guinea pig biliary motility both in vitro and in vivo. The first experiment compared contractile tension of gallbladder strips from young adult (6-12 months old) and 3-year-old guinea pigs in vitro. Contraction of gallbladder strips from the young guinea pigs was twice as forceful and was more sensitive to octapeptide of cholecystokinin (CCK-8) stimulation than the gallbladder strips from the older guinea pigs. The two groups were also studied in vivo by measuring changes in the intraluminal pressure of the gallbladder in response to exogenously administered doses of CCK-8. Young adult guinea pigs were more sensitive to CCK-8 at the lower doses tested and demonstrated gallbladder contractions that were more forceful than that of the old guinea pigs. CCK receptors were measured on gallbladder muscularis membranes from young adult and old guinea pigs. The number of receptors on gallbladder membranes decreased with age: 65.0 +/- 17.7 fmoles/mg protein on membranes from 1 year old; 7.9 +/- 2.0 fmoles/mg protein on membranes from 3 years old. The binding affinity of CCK receptors on gallbladder muscularis membranes for binding to CCK-8 was not significantly different in the two age groups studied. We conclude that age-related decreases in gallbladder responses to CCK-8 may be due to decreased concentrations of CCK receptors on gallbladder muscle cells.     

Neuropeptide Y-immunoreactive nerves in the uvea of guinea pig and rat

Neuropeptide Y (NPY)-immunoreactivity has been localized to a rich network of fibres in the uvea of guinea pig and rat. In the iris, NPY-immunoreactive nerves were present in iridial smooth muscle and around blood vessels; similarly throughout the choroid a dense network of NPY-immunoreactive fibres was found surrounding the choroidal vascularization. Following sympathectomy a marked decrease of NPY-immunoreactivity, in particular in the iris and less marked in the choroid, was noted, indicating that these fibres may originate at least in part from neuronal cell bodies in the superior cervical ganglion. The close relationship of the NPY-immunoreactive fibres to blood vessels in both anterior and posterior uvea is consistent with the established vasoconstrictor action of this peptide.     

PACAP modulation of the colon–inferior mesenteric ganglion reflex in the guinea pig

We investigated the effect of pituitary adenylate cyclase activating peptide (PACAP) on the colon–inferior mesenteric ganglion (IMG) reflex loop in vitro . PACAP27 and PACAP38 applied to the IMG caused a prolonged depolarization and intense generation of fast EPSPs and action potentials in IMG neurones. Activation of PACAP-preferring receptors (PAC1-Rs) with the selective agonist maxadilan or vasoactive intestinal peptide (VIP)/PACAP (VPAC) receptors with VIP produced similar effects whereas prior incubation of the IMG with selective PAC1-R antagonists PACAP6-38 and M65 inhibited the effects of PACAP. Colonic distension evoked a slow EPSP in IMG neurones that was reduced in amplitude by prolonged superfusion of the IMG with either PACAP27, maxidilan, PACAP6-38, M65 or VIP. Activation of IMG neurones by PACAP27 or maxadilan resulted in an inhibition of ongoing spontaneous colonic contractions. PACAP-LI was detected in nerve trunks attached to the IMG and in varicosities surrounding IMG neurones. Cell bodies with PACAP-LI were present in lumbar 2–3 dorsal root ganglia and in colonic myenteric ganglia. Colonic distension evoked release of PACAP peptides in the IMG as measured by radioimmunoassay. Volume reconstructed images showed that a majority of PACAP-LI, VIP-LI and VAChT-LI nerve endings making putative synaptic contact onto IMG neurones and a majority of putative receptor sites containing PAC1-R-LI and nAChR-LI on the neurones were distributed along secondary and tertiary dendrites. These results suggest involvement of a PACAP-ergic pathway, operated through PAC1-Rs, in controlling the colon–IMG reflex.     

Vagal origin of substance P-containing nerves in the guinea pig lung

This study reports on the possible origin and putative sensory nature of substance P-containing fibres in the lung. Following vagal ligation experiments, carried out on adult guinea pigs, the vagi, nodose ganglia and lungs were investigated by immunocytochemistry and radioimmunoassay. After ligation the lung showed a marked depletion of substance P-immunoreactivity; concomitantly there was an accumulation of immunoreactive material proximal to the ligature, indicating a peripheral direction of the peptide axonal flow. Several substance P-immunoreactive neuronal cell bodies were observed in the nodose ganglion. These results suggest that substance P-immunoreactive fibres in the lung might originate from primary sensory neurones in the nodose ganglion, which is compatible with other evidence that substance P has a sensory role.     

Morphological and physiological evidence for interstitial cell of Cajal-like cells in the guinea pig gallbladder

Gallbladder smooth muscle (GBSM) exhibits spontaneous rhythmic electrical activity, but the origin and propagation of this activity are not understood. We used morphological and physiological approaches to determine whether interstitial cells of Cajal (ICC) are present in the guinea pig extrahepatic biliary tree. Light microscopic studies involving Kit tyrosine kinase immunohistochemistry and laser confocal imaging of Ca²⁺ transients revealed ICC-like cells in the gallbladder. One type of ICC-like cell had elongated cell bodies with one or two primary processes and was observed mainly along GBSM bundles and nerve fibres. The other type comprised multipolar cells that were located at the origin and intersection of muscle bundles. Electron microscopy revealed ICC-like cells that were rich in mitochondria, caveolae and smooth endoplasmic reticulum and formed close appositions between themselves and with GBSM cells. Rhythmic Ca²⁺ flashes, which represent Ca²⁺ influx during action potentials, were synchronized in any given GBSM bundle and associated ICC-like cells. Gap junction uncouplers (1-octanol, carbenoxolone, 18β-glycyrrhetinic acid and connexin mimetic peptide) eliminated or greatly reduced Ca²⁺ flashes in GBSM, but they persisted in ICC-like cells, whereas the Kit tyrosine kinase inhibitor, imanitib mesylate, eliminated or reduced action potentials and Ca²⁺ flashes in both cell types, as well as associated tissue contractions. This study provides morphological and physiological evidence for the existence of ICC-like cells in the gallbladder and presents data supporting electrical coupling between ICC-like and GBSM cells. The results support a role for ICC-like cells in the generation and propagation of spontaneous rhythmicity, and hence, the excitability of gallbladder.     

Oscillatory and intrinsic membrane properties of guinea pig nucleus prepositus hypoglossi neurons in vitro

Numerous models of the oculomotor neuronal integrator located in the prepositus hypoglossi nucleus (PHN) involve both highly tuned recurrent networks and intrinsic neuronal properties; however, there is little experimental evidence for the relative role of these two mechanisms. The experiments reported here show that all PHN neurons (PHNn) show marked phasic behavior, which is highly oscillatory in approximately 25% of the population. The behavior of this subset of PHNn, referred to as type D PHNn, is clearly different from that of the medial vestibular nucleus neurons, which transmit the bulk of head velocity-related sensory vestibular inputs without integrating them. We have investigated the firing and biophysical properties of PHNn and developed data-based realistic neuronal models to quantitatively illustrate that their active conductances can produce the oscillatory behavior. Although some individual type D PHNn are able to show some features of mathematical integration, the lack of robustness of this behavior strongly suggests that additional network interactions, likely involving all types of PHNn, are essential for the neuronal integrator. Furthermore, the relationship between the impulse activity and membrane potential of type D PHNn is highly nonlinear and frequency-dependent, even for relatively small-amplitude responses. These results suggest that some of the synaptic input to type D PHNn is likely to evoke oscillatory responses that will be nonlinearly amplified as the spike discharge rate increases. It would appear that the PHNn have specific intrinsic properties that, in conjunction with network interconnections, enhance the persistent neural activity needed for their function.     

Role of amygdaloid nuclei in the anxiolytic-like effect of nociceptin/orphanin FQ in rats

We investigated the mechanism underlying the anxiolytic actions of the neuropeptide nociceptin/orphanin FQ (N/OFQ) using the elevated plus-maze test and T-maze test. Microinfusions of N/OFQ (10 or 32pmol) into the central amygdala (ACE) increased the time spent in the open arms of the elevated plus-maze (anxiolytic-like effects), whereas microinfusions of N/OFQ (10, 32 or 100 pmol) into the basolateral amygdala (ABL) did not affect the time spent in the open arms. Moreover, microinfusions of N/OFQ (32 pmol) into the ACE impaired escape performance from the open arms of the elevated T-maze (anxiolytic-like effects), but did not change inhibitory avoidance of the open arms. A non-peptidyl N/OFQ receptor (NOP) antagonist, J-113397(1-[(3R,4R)-1-cyclooctylmethyl-3-hydroxymethyl-4-piperidyl]-3-ethyl-1,3-dihydro-2H-benzimidazol-2-one) (10 mg/kg, s.c.), blocked the anxiolytic-like effects induced by N/OFQ. These results indicate that the anxiolytic-like effects of N/OFQ might be due to impaired escape performance from the open arms and it implicates the N/OFQ system within the ACE in the mediation of panic action.     

Effects of nociceptin/orphanin FQ in the acquisition of contextual and tone fear conditioning in rats

Nociceptin, or orphanin FQ (N/OFQ), the endogenous ligand of NOP receptors, is known to regulate learning and memory processes. To verify the role of N/OFQ in the acquisition of contextual (CFC) and tone fear conditioning (TFC), Wistar male rats received intracerebroventricular injections of N/OFQ (0.1-5.0 nmol) before training, and were tested 24 and 48 hr later to access the freezing response to context and tone, respectively. The intermediate doses (1.0 and 2.5 nmol) impaired the CFC test, sparing TFC. The highest dose (5.0 nmol) reduced freezing during both tests, a result that may be due to nonspecific effects. The posttraining injection of N/OFQ (1 or 5 nmol) did not interfere with CFC and TFC, suggesting a specific effect of the peptide in acquisition processes. Moreover, the impairment observed with N/OFQ (1 nmol) in CFC cannot be attributed to a state-dependent learning because it was not reversed by its pretest administration. The data support the negative role of N/OFQ in the acquisition of aversively motivated tasks, which encompass a spatial component and depend on the hippocampus.     

The uptake of horseradish peroxidase and its subsequent redistribution by guinea pig gallbladder in vivo

Horseradish peroxidase (HRP) was injected into the emptied gallbladder of guinea pigs at laparotomy. The fate of the HRP was observed by light and electron microscopy over the following 2 hr. Within 5 min. HRP appeared in pits and apical vesicles either as a rim of increased electron density or more evenly distributed throughout the pit or vesicle. The pits and vesicles were more frequently seen at the edge of the cell apex. From 15 min. HRP was identified in the basolateral cell space in increasing quantities with spill over through the basement membrane into the lamina propria: by 30 min. and 2 hr, little further change was observed. The quantity of nonspecific electron density in epithelial cell multivesicular bodies and residual bodies made the assessment of intracellular handling of the HRP impossible. Dilution of the HRP in the lamina propria made the identification of the eventual fate of the HRP difficult to determine.     

Architecture and age-related analysis of the neuronal number of the guinea pig intrinsic cardiac nerve plexus.

The aims of the present study have been to determine the architecture of the guinea pig intrinsic cardiac nerve plexus (ICNP) and to test whether or not the heart of this species undergoes decrease in neuronal number with aging. Nine young (3-4 weeks of age) and nine adult (18-24 months of age) animals were examined employing histochemistry for acetylcholinesterase to reveal the ICNP in total hearts. The number of intracardiac neurons in seven animals was assessed via counting of the nerve cells both on total hearts and in serial sections of the atrial walls. The intracardiac neurons from adult guinea pigs were amassed within 329 +/- 15 ganglia. The hearts of young animals contained significantly fewer ganglia, only 211 +/- 27. In adult guinea pigs approximately 60% of the intracardiac neurons were distributed within ganglia of not more than 20 neurons, but the ganglia of such size accumulated only 45% of the neurons in young animals. The total number of the intracardiac neurons estimated per guinea pig heart was 2321 +/- 215, and this number did not differ significantly between young and adult animals. The nerves entering the guinea pig heart were found both in the arterial and venous part of the heart hilum. The nerves from the arterial part of the heart hilum proceeded into the ventricles, but the nerves from the venous part of the hilum formed a nerve plexus of the cardiac hilum located on the heart base. Within the guinea pig epicardium, intrinsic nerves divided into six routes and proceeded to separate atrial, ventricular and septal regions. In conclusion, findings of this study contradict the age-related decrease of the neuronal number in the guinea pig heart and illustrate the remarkable similarity in the architecture of the intracardiac nerve plexuses between guinea pig and rat.     

Compensatory coding of body part location in autotopagnosia: Evidence for extrinsic egocentric coding

We report a patient with autotopagnosia (JD) who was unable to code the position of body parts relative to each other and who failed to update the position of body parts after passive movements. JD's performance in Studies 1–4 suggest that her ability to code the dynamic location of body parts with respect to each other ("intrinsic egocentric" spatial coding) was impaired, and that she employed a compensatory strategy by means of which the location of body parts was computed with respect to objects in the environment ("extrinsic egocentric" spatial coding). Studies 5–8 suggest that JD's ability to update hand position information was impaired after passive relative to active movements of her arm. For example, she was impaired in reaching to a target after passive but not active movements of her hand. Taken together, these findings extend previously reported functions of extrinsic egocentric coding to the localisation of body parts and demonstrate a possible dissociation between body part localisation dependent upon proprioceptive and efference copy information.     

Compensatory coding of body part location in autotopagnosia: Evidence for extrinsic egocentric coding

We report a patient with autotopagnosia (JD) who was unable to code the position of body parts relative to each other and who failed to update the position of body parts after passive movements. JD's performance in Studies 1-4 suggest that her ability to code the dynamic location of body parts with respect to each other ("intrinsic egocentric" spatial coding) was impaired, and that she employed a compensatory strategy by means of which the location of body parts was computed with respect to objects in the environment ("extrinsic egocentric" spatial coding). Studies 5-8 suggest that JD's ability to update hand position information was impaired after passive relative to active movements of her arm. For example, she was impaired in reaching to a target after passive but not active movements of her hand. Taken together, these findings extend previously reported functions of extrinsic egocentric coding to the localisation of body parts and demonstrate a possible dissociation between body part localisation dependent upon proprioceptive and efference copy information.