Ferenc Laczi

Differential responses in immunoreactive arginine-vasopressin content of microdissected brain regions during passive avoidance behavior

Immunoreactive arginine-vasopressin (IR-AVP) was measured in various hypothalamic and extrahypothalamic nuclei of male Wistar rats immediately after the 24 h retention test of a passive avoidance response. IR-AVP concentrations in paraventricular, suprachiasmatic and lateral septal nuclei were significantly decreased in comparison with the non-shocked rats, while IR-AVP was increased in the central amygdala nucleus, subfornical organ and locus coeruleus. No significant differences in IR-AVP levels were found in the habenular and periventricular hypothalamic nucleus, organum vasculosum of lamina terminalis and medial and dorsal raphe nucleus.

Arginine-vasopressin content of hippocampus and amygdala during passive avoidance behavior in rats

Arginine-vasopressin (AVP) is involved in memory processes. The memory effects of AVP are mediated by neuronal mechanisms taking place in limbic-midbrain structures. Therefore, immunoreactive AVP (IR-AVP) was measured in hippocampus and amygdala of male Wistar rats during acquisition and retention of passive avoidance behavior. IR-AVP concentration was decreased in the hippocampus immediately after the learning trial while IR-AVP content of the amygdala was not affected. Animals that showed the passive avoidance response (good avoiders) at the 24 h or 120 h retention test had a reduced IR-AVP concentration in the hippocampus immediately after the test. However, IR-AVP content of the hippocampus was not different from that of non-shocked control animals when measured immediately before the 120 h retention test. Poor avoiders that showed only minor avoidance behavior did not differ in hippocampal IR-AVP content from non-shocked control animals. IR-AVP content of the amygdala was also not altered after the retention session. These effects on IR-AVP content could only be shown in animals that were trained and habituated to the passive avoidance procedure. Such trained and habituated animals had an IR-AVP level in the hippocampus which did not differ from that of animals that were left undisturbed until sacrifice. When the animals were not trained, but placed for the first time in the passive avoidance apparatus without being exposed to the learning trial, the hippocampal IR-AVP content was reduced.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute morphine treatment and morphine tolerance/dependence alter immunoreactive oxytocin levels in the mouse hippocampus

Immunoreactive oxytocin levels were measured in the mouse hippocampal tissue (h-OXT). Acute morphine treatment increased h-OXT, which effect was reversed by naloxone. In mice rendered tolerant to and dependent on morphine h-OXT was lower than in placebo pellet-implanted control mice. In the tolerant/dependent animals naloxone resulted in precipitated withdrawal syndrome which was associated with a slight increase in h-OXT. The data indicate that h-OXT is affected by acute morphine treatment and by morphine tolerance/dependence and raises the possibility that h-OXT participates in the adaptive response of the organism towards narcotic drugs.

Levels of arginine-vasopressin in cerebrospinal fluid during passive avoidance behavior in rats.

The concentration of immunoreactive arginine-vasopressin (IR-AVP) was measured in the cerebrospinal fluid (CSF) during acquisition and retention of passive avoidance behavior. IR-AVP level in CSF of male Wistar rats immediately after the learning trial was increased; the rate of which was related to the intensity of the electric footshock during the learning trial and the avoidance latency as measured 1 day after the learning trial. Immediately after the 24 h retention test IR-AVP levels were significantly increased in rats subjected to the low (0.25 mA) shock intensity during the learning trial, but IR-AVP levels of rats exposed to the high shock (1.0 mA) were under the limit of detection. If the retention test was postponed till 5 days after the learning trial, the increase of IR-AVP level in the CSF was related to avoidance latencies which reflect the intensity of aversive stimulation (electric footshock). The results suggest an association between central AVP release and passive avoidance behavior and may be indicative of the role of this peptide in neuronal mechanisms underlying learning and memory processes.

Antidiuretic activity and immunoreactive arginin-vasopressin levels in eye plexus blood during passive avoidance behavior in rats

Abstract Experiments were designed to investigate the release of endogenous vasopressin (AVP) as related to passive avoidance behavior and the significance of circulating AVP levels for memory processes using a radioimmunoassay (RIA) and bioassay (AD activity). The levels in plasma obtained from eye plexus blood were very high. A good correlation was found between AD activity and immunoreactive AVP (y = 21.10 + 3.00x, r = 0.895, n = 59). Vasopressin levels in eye plexus blood of male rats were significantly higher than in female rats. The rate of AVP release in Wistar and Brattleboro homozygous normal rats at the 24 h retention test was related to the intensity of the electric footshock during the learning trial and the avoidance latency at the 24 h retention test. The release of AVP immediately after the learning trial was much higher than after the 24 h retention test. Blood levels were not different whether rats received electric footshock or not and were not related to the intensity of the aversive stimulus or to passive avoidance latencies at the 24 h retention test. Brattleboro homozygous diabetes insipidus rats, which had no detectable vasopressin levels in eye plexus blood failed to show passive avoidance behavior even after exposure to high shock intensity. Rats heterozygous for diabetes insipidus exhibited maximal avoidance when a high shock intensity was used. Plasma AVP levels of these rats were however not different from those measured in non-shocked rats either after the learning trial or the 24 h retention test. Passive avoidance behavior was markedly attenuated in male Wistar rats treated with AVP antiserum icv either before the learning trial or the 24 h retention test. This treatment prevented AVP release at the retention trial but not after the learning trial. These results suggest that the long term memory effect originates from AVP of central origin.

Vasopressin and oxytocin content in cerebrospinal fluid and in various brain areas after administration of histamine and pentylenetetrazol

The content of vasopressin (AVP) and oxytocin (OXT) in the septum, hippocampus, hypothalamus and cortex was determined at 5 min and 24 hr after peripheral (intraperitoneal) administration of histamine (20.0 mg/kg) and pentylenetetrazol (45.0 mg/kg) and in the cerebrospinal fluid at 24 hr after pentylenetetrazol treatment. At 5 min after administration of histamine the AVP content in the septum was increased whereas the OXT level in the various areas was not changed. At 24 hr, neurohypophyseal peptide contents were unaffected in the brain regions analyzed. Pentylenetetrazol did not alter AVP content at 5 min after its administration, however, the OXT level in the septum and the cortex was diminished. At 24 hr after administration of pentylenetetrazol a decreased AVP content in the hippocampus and in the cortex was observed. In contrast, OXT content in the cortex was increased at this time. AVP and OXT levels in CSF were not changed at 24 hr following pentylenetetrazol treatment. The present results suggest that the levels of neurohypophyseal hormones can be differentially altered in particular brain regions at short- (5 min) and long- (24 hr) term intervals after treatment with histamine or pentylenetetrazol. Long-term changes in AVP and OXT levels after pentylenetetrazol may be implicated in the amnesic properties of this convulsive drug. Furthermore, the present findings point to a possible relationship with previously reported pentylenetetrazol-induced changes in peptide levels in the CSF.

Presence of chromatographically identified oxytocin in human sensory ganglia

Oxytocin-like immunoreactivity (IR-OXT) was detected in extracts of human spinal L5 and Gasserian ganglia by a radioimmunoassay (RIA) specific to oxytocin (OXT) and was identified by high-performance liquid chromatography (HPLC). One of the two immunoreactive peaks obtained on HPLC was found to elute at the same position as the OXT standard. The results reveal the presence of chromatographically identified OXT immunoreactivity in human sensory ganglia.

Effects of β-endorphin2–9 on arginine-8-vasopressin and oxytocin levels in hypothalamic and limbic brain regions

Immunoreactive arginine-8-vasopressin (AVP) and oxytocin (OXT) were measured in rat hypothalamic and limbic brain regions after the intracerebroventricular administration of beta-endorphin fragment 2-9 (beta E2-9). The peptide decreased the AVP content of the hippocampus and the OXT levels in the septum and amygdala. The present data favor the view that beta E2-9 interacts with limbic AVP- and OXT-systems.

Pharmacokinetics of DGAVP in plasma following intranasal and oral administration to healthy subjects

A pharmacokinetic study was carried out to assess the bioavailability of desglycinamide-[Arg8]vasopressin (DGAVP, Org 5667). DGAVP (2 mg) was administered both intranasally and orally to healthy subjects with a treatment interval of 1 week. Blood samples were taken regularly between 15 min before and 210 min after administration and were assayed for DGAVP by radioimmunoassay. In all subjects endogenous vasopressin (AVP) levels were detectable. Peak levels of DGAVP occurred at 15 min after both treatments. The mean absorption half-life was 8.7 and 7.3 min and the mean elimination half-life was 38 and 34.6 min for the intranasal and oral route of administration, respectively. The bioavailability of orally administered DGAVP was low compared with the intranasally administered drug; the relative bioavailability of oral/nasal administration was 0.7%. The results indicate that DGAVP is absorbed rapidly after both oral and intranasal administration, but the intranasal route of administration of DGAVP is 100 times more effective in increasing plasma DGAVP levels.

Characterization of oxytocin immunoreactivity in human sympathetic paravertebral ganglia

Immunoreactive oxytocin (IR-OXT) detected in extracts of human lumbar sympathetic paravertebral ganglia was characterized by high-performance liquid chromatography (HPLC). The immunoreactive substance was found to elute at the same position as the reference preparation of oxytocin (OXT). The results revealed the presence of chromatographically identified OXT in human sympathetic ganglia.