Studies of a possible relationship of brain proteins to changes in behavioral sensitivity to DFP

Whether behavioral differences in selectively bred lines of rats could be attributed to changes in the enzymes acetylcholinesterase and glutathione S-transferase in different brain regions have been examined. Electrophoresis of the brain proteins has been studied and compared to one another and to that of control animals. The results presented suggest that differences in behavior are associated with changes in the level of brain enzymes, although not with changes in the properties of the enzymes $\text{per}$$\text{se}$.     

Increased behavioral and neuronal sensitivity to sex pheromone after brief odor experience in a moth

Plasticity in the response to stimuli related to food and oviposition cues is well documented in insects. However, responses to cues related to reproduction, for example, sex pheromones, are considered to be innate and thus not affected by experience. Here we show that brief preexposure to sex pheromones, without ensuing reward, lowers the threshold for behavioral response and augments the sensitivity in antennal lobe interneurons to pheromone compared with naive male moths. Thus, the sex pheromone system in insects can be modulated by experience. In addition, we show that the behavioral attraction to sex pheromone increases after preexposure in a time-dependent manner: a short-term effect, possibly a form of sensitization, and a long-term effect after more than 24 h. The behavioral long-term effect is paralleled by an increase in sensitivity of interneurons in the primary olfactory center, whereas the peripheral olfactory system does not change its sensitivity. We hypothesize that short-term sensitization to sex pheromone serves as a kind of alert system, whereas the long-term effect improves male performance when reproductively active females are present.     

Effects of septal lesions on behavioral sensitivity of female rats to gonadal hormones

Spayed female rats were given bilateral septal lesions or a sham operation and 3 wk later tested for hormone-induced female sexual behavior. When primed with 0.5, 1.0, or 2.0 μg of estradiol benzoate (EB) per day for 3 days and tested for lordosis behavior on the fourth day, animals with septal lesions showed a positive dose-related increase in mean lordosis quotient (LQ), whereas control animals showed a low mean LQ for all doses of EB. After priming with a low dose of EB (0.5 μg/day for 3 days), progesterone administration prior to behavior testing on day 4 produced a comparable facilitation in LQ for both septal-lesioned and sham-operated animals. When treated for 3 days with either 50 or 150 μg of testosterone propionate (TP) and given progesterone prior to behavior testing on day 4, female rats with septal lesions showed a higher mean LQ than sham-operated rats. Thus, septal lesions increase the behavioral sensitivity of female rats to both EB and TP as measured by female sexual behavior, but do not appear to alter the responsiveness of animals to progesterone.     

Marked behavioral and biochemical sensitivity to lesion size in the posterior cortex of the rat

Unilateral focal cortical suction lesions of varying diameter from 0.7 to 2.0 mm were made in the right posterior lateral cortex of rats. Only the 1.0 mm lesion size resulted in spontaneous postoperative hyperactivity. This increased activity was accompanied by significantly elevations in substantia nigra and caudate nucleus dopamine concentrations. Other lesion sizes did not effect behavior or brain biochemical concentrations in this fashion. These results suggest a functional organization in this area of posterior cortex which affects both neurochemistry and behavior.     

Reflex responses to reductions in functioning renal mass

Both acute unilateral nephrectomy (AUN) and unilateral ureteral obstruction (UUO) result in an acute increase in cation excretion from the contralateral kidney. AUN results in reflex changes in systemic hemodynamics owing to an acute and transient increase in arterial pressure that activates carotid sinus baroreceptors and constitutes an afferent limb in the reflex; hemodynamic adjustments and increased cation excretion result. The reflex involves participation of the endogenous opioid system, with receptors located primarily in the central nervous system, and requires intact pituitary function because both hypophysectomy and pretreatment with large doses of dexamethasone prevent the postnephrectomy natriuresis. The natriuresis is closely correlated with an increase in the plasma concentration of the NH2-terminal fragment of the pituitary peptide precursor molecule proopiomelanocortin, which suggests that such a peptide could participate directly or indirectly in the postnephrectomy natriuresis. Surgical denervation of either the ipsilateral or the contralateral kidney markedly alters the response to AUN, which prevents the natriuresis and blunts the kaliuresis, and indicates a role for renal neural reflexes. Renorenal reflex pathways also mediate the response of the contralateral kidney to UUO, because denervation of either the ipsilateral (obstructed) or the contralateral kidney abolishes both the natriuresis and kaliuresis usually seen after UUO. This reflex also involves the endogenous opioid system, for it does not occur in rats receiving an i.v. infusion of the opiate receptor antagonist naloxone.     

Respiratory responses to opiates applied to the medullary ventral surface

The participation of the medullary structures in the total respiratory effect of opiates was studied by restricting the access of the delta-agonist D-ala2-D-leu5-enkephalin and the mu-agonist D-ala2-Me-Phe4-Met (O) ol5-enkephalin, to the ventral medullary surface, and by comparing their responses with those induced after i.c.v. administration. The medullary structures were more resistant to the overall depressant action. The opioids in the medulla depressed preferentially the tidal volume and the CO2-responsivity whereas the i.c.v. injections affected severely the frequency. No qualitative differences were found between the effects of the delta- and mu-agonist. It is concluded that both, medullary and supramedullary structures are involved in the respiratory response to opiates, but they participate with unique functions in the overall respiratory effect.     

Association between olfactory sensitivity and behavioral responses of Drosophila suzukii to naturally occurring volatile compounds

Drosophila suzukii Matsumura (Diptera: Drosophilidae) is an invasive, destructive crop pest that originated in South East Asia. D. suzukii recently invaded Western countries and is threatening both European and American fruit industries. It is extremely attracted to otherwise undamaged, ripening fruits, unlike most other Drosophila species that attack only decaying or rotten fruits. Recent studies on different insect species showed that several naturally occurring compounds of easy market availability showing deterrent action may be used to supplement mass catches with food traps. Based on these considerations, the aim of the present work was to test the effects of some natural compounds (alone or in the mixture) on the olfactory system of the D. suzukii and the behavioral responses evoked. We measured by electroantennogram (EAG) recordings, the olfactory sensitivity of antennae to increasing concentrations of eugenol, vanillin, menthol, cis-jasmone; eugenol + vanillin, +menthol, +cis-jasmone; vanillin + menthol, +cis-jasmone. In addition, the behavioral responses to the same compounds and mixtures were evaluated. Our electrophysiological results show a dose-response relationship between the EAG amplitudes and the increasing concentrations of the olfactory compound. The behavioral results show that the number of laid eggs is significantly different between the standard diet and the standard diet + natural compound. These results underline a specificity in the olfactory sensitivity and in the ovipositing behavior of D. suzukii females; also, they could be valuable for the identification of key chemicals aimed at the future development of strategies in the management and control of this harmful insect for crops.     

Inhibitory Kcnip2 neurons of the spinal dorsal horn control behavioral sensitivity to environmental cold

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Diminished behavioral and neural sensitivity to sound modulation is associated with moderate developmental hearing loss

The acoustic rearing environment can alter central auditory coding properties, yet altered neural coding is seldom linked with specific deficits to adult perceptual skills. To test whether developmental hearing loss resulted in comparable changes to perception and sensory coding, we examined behavioral and neural detection thresholds for sinusoidally amplitude modulated (sAM) stimuli. Behavioral sAM detection thresholds for slow (5 Hz) modulations were significantly worse for animals reared with bilateral conductive hearing loss (CHL), as compared to controls. This difference could not be attributed to hearing thresholds, proficiency at the task, or proxies for attention. Detection thresholds across the groups did not differ for fast (100 Hz) modulations, a result paralleling that seen in humans. Neural responses to sAM stimuli were recorded in single auditory cortex neurons from separate groups of awake animals. Neurometric analyses indicated equivalent thresholds for the most sensitive neurons, but a significantly poorer detection threshold for slow modulations across the population of CHL neurons as compared to controls. The magnitude of the neural deficit matched that of the behavioral differences, suggesting that a reduction of sensory information can account for limitations to perceptual skills.     

Morphine-6-glucuronide contributes to rewarding effects of opiates

It was recently confirmed that a metabolite of morphine, morphine-6-glucuronide (M6G), is a long lasting, powerful analgesic in humans and animals and may account for a major component of clinical opiate analgesia. It is reported here that M6G is also a powerful behavioral reinforcer in the conditioned place preference test in rats, indicating that it has rewarding properties, and is therefore likely to have abuse potential. The induction of a place preference by M6G is blocked by naltrexone, indicating that the rewarding effect of M6G is mediated by opioid receptors. Given systemically M6G is approximately equipotent with morphine. When given intracerebroventricularly to bypass the blood-brain barrier, M6G is 146 times more potent than morphine in the place preference test. Thus 6-substituted metabolites of opiates may play a more significant role in the effects of opiates than has been previously assumed.     

Endogenous opiates modulate release of growth hormone in response to electroacupuncture

The effect of electroacupuncture on serum growth hormone levels was investigated in 5 normal subjects and in 10 patients with chronic musculoskeletal pain. Serum growth hormone did not change in the normal subjects but there was an approximate 5-fold increase in the chronic pain subjects. This effect was partially inhibited by prior administration of the opiate antagonist naloxone, suggesting that the rise in growth hormone was mediated via release of central nervous system opioids.     

Endogenous opiates: 1987

This paper is the tenth installment of our annual review of the research during the past year involving the endogenous opiate system. It covers the nonanalgesia and behavioral studies of the opiate peptides published in 1987. The specific topics this year include stress; tolerance and dependence; eating; drinking; gastrointestinal and renal activity; learning, memory, and reward; cardiovascular responses; respiration and thermoregulation; seizures and other neurological disorders; electrical activity; locomotor activity; sex, pregnancy, and development; immunology and cancer; and other behavior.     

Endogenous opiates: 1988

This paper is the eleventh installment in our annual review of the research during the past year involving the endogenous opiate system. It is concerned with nonanalgesic and behavioral studies of the opiate peptides that were published during 1988. The specific topics this year include stress; tolerance and dependence; eating; drinking; gastrointestinal, renal, and hepatic functions; mental illness; learning, memory, and reward; cardiovascular responses; respiration and thermoregulation; seizures and other neurological disorders; electrical activity; locomotor activity; sex, pregnancy, and development; immunology and cancer; and other behavior.     

Endogenous opiates: 1995

This article is the eighteenth installment of our annual review of research concerning the opiate system. It includes articles published during 1995 reporting the behavioral effects of the opiate peptides and antagonists, excluding the purely analgesic effects. The specific topics covered this year include stress; tolerance and dependence; eating; drinking; gastrointestinal, renal, and hepatic function; mental illness and mood; learning, memory, and reward; cardiovascular responses; respiration and thermoregulation; seizures and other neurological disorders; electrical-related activity; general activity and locomotion; sex, pregnancy, and development; immunological responses; and other behaviors.     

Endogenous opiates: 1986

This is the ninth installment of our annual review of research involving the endogenous opiate peptides. It is restricted to the non-analgesic and behavioral studies of the opiate peptides published in 1986. The specific topics this year include stress; tolerance and dependence; eating; drinking; gastrointestinal, renal, and hepatic processes; mental illness; learning, memory, and reward; cardiovascular responses; respiration and thermoregulation; seizures and other neurological disorders; activity; sex, pregnancy, and development; and some other behaviors.     

Endogenous opiates: 1982

This article is the fifth installment in an annual series of reviews of successive year's research dealing with the endogenous opiate peptides. Due to the continuing massive increase in the number of studies in this field, it has become impossible to continue comprehensive reviews of all aspects of this work. As a result we have decided that beginning this year the coverage will be abbreviated to emphasize non-analgesic and behavioral work. The specific areas discussed include stress, tolerance and dependence, consummatory responses, alcohol consumption, schizophrenia and emotional disorders, learning and memory, cardiovascular responses, respiratory effects, thermoregulatory effects, neurological deficits and other disorders, activity, and other, miscellaneous behaviors. As in previous years, we have attempted a relatively comprehensive review of the subjects covered only for the previous year and have not made an attempt to evaluate their contributions relative to those of past years.     

Endogenous opiates: 1980

Vast amounts of research have been done that have attempted to delineate the pharmacological and physiological effects of the endogenous opiate peptides. A great deal of knowledge has also been accumulated in a limited time span concerning the types and locations of the opiate receptors and peptides, as well as their functions. In 1980, reports were made concerning the effects of these peptides on analgesia, on tolerance and dependence, on activity, on learning and memory, on schizophrenia and other types of emotional disturbances, and on physiological responses such as eating and drinking, cardiovascular responses, and sexual function. Additional understanding was also gained concerning their interactions with neurotransmitters, other neuropeptides, and hormones. These and other studies published only in 1980 are reviewed in this paper, which is the third of an annual series.     

Endogenous opiates: 1979

Since the discovery in 1971 of opiate receptors and later of the opiate-like peptides, there has been widespread interest in determining their exact localization, number and kinds, nature, and physiological and pharmacological functions. Between 1971 and 1978, vast amounts of research investigated these problem areas, but in 1979 alone the literature on the opiate peptides nearly doubled. This review is the second of an annual series and summarizes the highlights of the work published during 1979.