CRF-induced excessive grooming behavior in rats and mice

We studied the grooming response to lateral ventricle injection of CRF in both rats and mice under similar conditions. One microgram of CRF ICV induced a pronounced increase (3- to 4-fold) in the frequency of self-grooming in rats, but only a much smaller (less than 20%) increase in mice. The minimum effective dose of CRF in rats was 300 ng. Although ACTH1-24 induced less grooming in mice than in rats, the difference in potency did not appear to be sufficient to explain the differences between the effectiveness of CRF in the two species. Whereas ACTH increased all types of grooming scored. CRF increased all forms of grooming except flank scratching with the hind limb. The major effect of CRF was to increase the number of episodes of grooming, whereas ACTH1-24 tended to prolong the length of individual episodes. The excessive grooming induced by ICV CRF was not affected by prior treatment with dexamethasone, suggesting that the increased grooming was not due to secondary release of ACTH from the pituitary. Nevertheless, ICV CRF might induce grooming by releasing MSH/ACTH from cerebral storage sites. CRF-induced grooming, like ACTH-induced grooming, was inhibited by naloxone pretreatment. Despite the small qualitative differences, CRF-induced grooming could be due to secondary release of ACTH.     

Alpha-MSH injected into the substantia nigra or intraventricularly alters behavior and the striatal dopaminergic activity

Rats were injected with 1 μg of alpha-melanocyte stimulating hormone (α-MSH) into the third ventricle and locally in the ventral tegmental area and in different regions of the substantia nigra. The modifications produced on grooming behavior and locomotion as well as on the dopamine content of the nucleus accumbens and the caudate putamen, were studied. Both intraventricular peptide administration and microinjections into the ventral tegmental area induced excessive grooming and a significant increase of the locomotor activity. The dopamine content of the nucleus accumbens and caudate putamen was markedly reduced. Injections of the peptide into the substantia nigra pars compacta failed to induce excessive grooming but did provoke a slight increase in locomotor activity and a smaller change in caudate dopamine content than that observed by injections in the ventral tegmental area or in the third ventricle. Dopamine levels in the nucleus accumbens were not changed. Finally, the injections of α-MSH into the lateral substantia nigra did not produce either biochemical or behavioral changes.The results suggests that α-MSH can modify, directly or indirectly, the striatal dopaminergic activity and that the behavioral alterations observed such as excessive grooming, could be mediated by the activation of the dopamine cells from the ventral tegmental area, that in turn may provoke a significative release of dopamine at the caudate putamen nucleus as well as in nucleus accumbens.     

Limbic-midbrain lesions and ACTH-induced excessive grooming.

The induction of excessive grooming by intraventricular administration of ACTH_1–24 was studied in rats with lesions in midbrain-limbic structures. Such areas have been reported to be implicated in mediating ACTH-induced effects on avoidance behavior, sexual excitement or stretching and yawning. Electrolytic lesions in the septal complex, the anterior hypothalamic/preoptic area, the mammillary bodies, the amygdala, the posterior thalamus and dorsal or ventral hippocampus did not interfere with ACTH-induced excessive grooming. Lesioning of the hippocampal complex by aspiration led to an inhibition of excessive grooming depending on the degree of hippocampal damage. Amygdala and hippocampal lesions enhanced the display of stretching and yawning activity after treatment with the peptide. The data indicate differences in the neural substrates mediating the effect of ACTH on extinction of conditioned avoidance behavior, excessive grooming, sexual excitement and stretching and yawning.     

Intracerebroventricular ACTH activates the pituitary-adrenal system:dissociation from a behavioral response.

In the rat, intracerebroventricular injection of synthetic ACTH (ACTH_1–24, ACTH_1–16) elevated plasma corticosterone levels and induced the display of excessive grooming behavior. The grooming response could be elicited in hypophysectomized rats without concommittant elevation of plasma corticosterone. In intact rats subcutaneous injection of ACTH_1–24 and not of ACTH_1–16-NH₂ stimulated the release of adrenal corticosteroids, whereas no excessive grooming was observed. In contrast to the reduced effectiveness of a second icv injection of ACTH in inducing the behavioral response, no single-dose tolerance was observed for the effect of icv ACTH on the pituitary-adrenal system. Therefore it was concluded that two different central mechanisms underly the observed responses to the icv applied ACTH.     

The colliculus superior modulates ACTH-induced excessive grooming

In previous studies the involvement of nigrostriatal dopaminergic activity in ACTH(1-24)-induced grooming has been established. It was suggested that the dopaminergic modulation of ACTH(1-24)-induced excessive grooming is exerted through the striato-nigro-collicular pathway. To obtain further evidence it was investigated, whether local application of GABAergic agents into the colliculus superior modulates excessive grooming occurring after an intraventricular injection with ACTH(1-24). It appeared that intra-collicular picrotoxin (a GABAergic antagonist) suppressed ACTH-induced grooming, whereas muscimol (a GABAergic agonist) enhanced the grooming response. The picrotoxin-induced R(unning) F(it) B(ehavior), elicited from the colliculus superior was also seen after intraventricular administration of picrotoxin. A detailed comparison of this behavioral response seen after both routes of administration of picrotoxin suggests that intraventricularly injected picrotoxin may well induce the RFB via a direct effect on the colliculus superior. Lesions placed in the colliculus superior completely abolished picrotoxin-induced RFB, exploration and orientation behavior. Yet, these lesions did not reduce excessive grooming suggesting that although this region may be involved in the modulation of ACTH-induced grooming it is not the primary site of peptide action.     

ACTH-induced excessive grooming in the rat: the influence of environmental and motivational factors.

Intraventricularly administered ACTHt_1–24 in rats initiated excessive grooming followed by stretching and yawning syndrome. The present study provides evidence that novelty is not an essential prerequisite for its expression and that a variety of environmental variables is not able to influence the peptide-induced behavior. Only very strong motivational variables as severe hunger/thirst and anxiety are able to modulate the ACTH-initiated excessive grooming: This response is significantly depressed in water-deprived rats bar pressing for water in a Skinner box, as well as in rats receiving unavoidable electric foot shock. The results are indicative of the strength of the ACTH-initiated motivation to groom, and it is suggested that excessive grooming is a secondary response serving to dearouse the organism after activation by ACTH.     

Some characteristics of TRH-induced grooming behavior in rats

Intracerebroventricular administration of TRH induces excessive grooming behavior that is characterized by an important contribution of the elements scratching and paw licking. As compared with other grooming inducing peptides, the pattern of TRH-induced grooming resembles that induced by beta-endorphin rather than those elicited by ACTH or bombesin. TRH-induced excessive grooming is suppressed by pretreatment with haloperidol, naloxone or neurotensin. Haloperidol suppresses TRH-induced grooming in a general way, whereas the suppressive effect of the other drugs is mainly due to a selective reduction of TRH-induced excessive scratching. Combined treatments of rats with TRH and a submaximal dose of ACTH, bombesin or beta-endorphin do not result in higher grooming scores than with single peptide treatment. Excessive grooming elicited by water immersion is not affected by TRH. It is concluded that TRH is undoubtedly an excessive grooming inducing peptide. In situations where excessive grooming is elicited by other peptides or by water immersion, TRH does not further activate the operating systems involved in the existing excessive grooming.     

Peptide-induced excessive grooming in the rat: The role of opiate receptors

We have investigated the possibility that opiate peptides induce excessive grooming behavior in the rat via a direct action on an opiate receptor by comparing the opiate agonist dynorphin(1–13) with its non-opioid fragment des-tyrosine¹-dynorphin(1–13) (dT-Dyn). We have shown that both peptides are capable of inducing grooming and that this behavior can be suppressed by pretreatment with naloxone. Analysis of the grooming pattern revealed that the response induced by dT-Dyn is qualitatively similar to that induced by ACTH(1–24) and dynorphin(1–13). Cross-tolerance was demonstrated among the various peptides. We conclude that peptide-opiate receptor interaction is not the primary event in the induction of grooming and that the opiate receptor(s) involved are located at another site underlying peptide-induced grooming.     

Dopamine depletion in nucleus accumbens reduces ACTH1–24-induced excessive grooming

Animals were pretreated with 6-OHDA or ascorbate vehicle injected into the nucleus accumbens and tested 10 days later for excessive grooming induced by intracerebroventricular injection of ACTH_1–24. The animals pretreated with 6-OHDA showed a significant decrease in excessive grooming produced by the neuropeptide and this reduction was seen only in the last 30 minutes of a 60-min test session. The results suggest an interaction of ACTH with dopamine systems on the onset and maintenance of excessive grooming.     

Behavioral activation by CRF: evidence for the involvement of the ventral forebrain

Rats injected intracerebroventricularly with corticotropin releasing factor (CRF) at the level of the lateral ventricle or cisterna magna showed a dose-dependent increase in locomotor activity. The increase in locomotor activity from injections of CRF into the cisterna magna was blocked by a cold cream plug in the cerebral aqueduct. An identical plug failed to block the increase in locomotor activity produced by CRF injected into the lateral ventricle. Intracerebral injections of CRF produced a site specific increase in locomotor activity with the largest increases observed from CRF injected into the substantia innominata/lateral preoptic area. Results suggest that the locomotor activating effects of CRF may be due to an activation of CRF receptors in the ventral forebrain, a region rich in CRF cell bodies and projections.     

Participation of the cholinergic system in the excessive grooming behavior induced by neuropeptide (N) glutamic acid (E) isoleucine (I) amide (NEI)

The neuropeptide (N) glutamic acid (E) isoleucine (I) amide (NEI) injected into the ventral tegmental area (VTA) or intraventricularly (icv) induces excessive grooming behavior (EGB) and motor activity (MA). Here, we studied whether the cholinergic system is involved in the NEI-induced behavior. The present results demonstrate that atropine, a general muscarinic antagonist, injected icv previous to NEI, suppresses the behavior provoked by icv injections of the peptide, whereas the prior icv injection of dyhidro--erythroidine, a general nicotinic antagonist, did not affect the EGB and MA induced by the peptide. From the experimental evidence, it is suggested that NEI may act specifically on a cholinergic afferent to dopaminergic cells. Also, the results appear to indicate that a neural target, different from the dopamine system, may be activated by the peptide to elicit behavioral changes, such as EGB.     

Identification of chemosensory sensilla activating antennular grooming behavior in the Caribbean spiny lobster,Panulirus argus

Crustaceans such as crabs and lobsters clean or 'groom' their olfactory organ, the antennule, by wiping it through a pair of mouthpart appendages, the third maxillipeds. In the lobster, only a few chemicals found in prey extracts, especially glutamate, elicit grooming. Chemosensory input driving grooming is likely to be mediated via sensilla located on antennules and third maxillipeds. Chemosensory antennular sensilla are innervated by neurons with central projections either to the glomerular olfactory lobe (aesthetasc sensilla) or to non-glomerular antennular neuropils (nonaesthetasc sensilla). By selectively ablating the chemosensory sensilla on the antennules and the third maxillipeds we have determined that the aesthetascs are necessary and sufficient to drive grooming behavior. Chemosensory activation of antennular grooming behavior likely follows a 'labeled-line' model in that aesthetasc neurons tuned to glutamate provide adequate input via the olfactory lobe to motor centers in the brain controlling antennular movements.     

Pressor, tachycardic and behavioral excitatory responses in conscious rats following ICV administration of ACTH and CRF are blocked by naloxone pretreatment

Experiments were conducted to compare the blood pressure and heart rate responses of conscious rats given intracerebroventricular (ICV) injections of adrenocorticotropin (ACTH 1-24) and corticotropin releasing factor (CRF). Under sodium pentobarbital anaesthesia, rats were implanted with a stainless-steel cannula into the lateral cerebral ventricle and had their right femoral artery and vein cannulated. Upon recovery (24-48 hr later) conscious, unrestrained rats were given ICV injections (total volume 5 microliter by gravity flow) of sterile saline, ACTH (1-24) (0.85 and 1.7 nmoles) or CRF (0.55 and 1.1 nmoles) and blood pressure and heart rate were monitored over the next 2 hr (from the abdominal aorta via the femoral arterial catheter). Both ACTH and CRF caused mean arterial pressure (MAP) to increase, which was paralleled with increases in mean heart rate (MHR). Moreover, these elevations in MAP and MHR were temporally associated with excessive grooming (for ACTH) and locomotor activity (for CRF), which occurred before and lasted as long as MAP and MHR were enhanced. Intravenous (IV) pretreatment whereby naloxone was given 10 min before ICV administration of ACTH (1.7 nmoles) or CRF (1.1 nmoles), showed that naloxone blocked the behavioral, pressor and tachycardic effects of both ACTH and CRF. The results demonstrate that the pressor, tachycardic and locomotor effects evoked in conscious rats by ICV administration of ACTH or CRF are antagonized by naloxone and that their hemodynamic changes may, in part, be mediated by prior behavioral activation.     

Lesions of the anteroventral third ventricle region exaggerate neuroendocrine and thermogenic but not behavioral responses to a novel environment

Mild psychological stressors provoke an acute rise in core temperature (T(C)), stimulate the hypothalamo-pituitary-adrenocortical (HPA) axis, and induce various stress-related behaviors. In the present study, we examined the effect of ablation of the anteroventral third ventricle region (AV3V) on both physiological and behavioral responses to a novel environment. T(C) was monitored in male Sprague-Dawley rats, with either sham or AV3V lesions, during a 5-h exposure to a novel environment. Trunk blood was collected, in a second group of rats, for the assessment of plasma levels of ACTH and corticosterone. Novelty-induced grooming and rearing behaviors were assessed in a third group of animals. T(C) was elevated in all animals after 30 min in the novel environment, but the rise was exaggerated in rats with AV3V lesions ( approximately 0.5 degrees C). AV3V-lesion rats maintained a higher core temperature for 2 h before it returned to the same level as the control group. Plasma levels of ACTH and corticosterone were also exaggerated in the AV3V lesion group after 30 min in a novel environment. In contrast to the physiological responses, the behavioral measures of grooming and rearing revealed no differences between the groups. The results from the current study suggest that neurons within the AV3V region exert an inhibitory influence on the HPA axis and fever developed in response to stressful psychological stimuli. They also confirm that the physiological and hormonal components of the stress response are independent of certain behavioral measures of stress.     

The third ventricle of monkeys

Summary Surface features of the ependymal lining of the third ventricle in mature male and female monkeys have been investigated with scanning electron microscopy (SEM). Broad aspects of third ventricular morphology from three species of monkey are similar regardless of sex. The lateral walls are heavily ciliated whereas the ventral floor and most ventral parts of the lateral walls are not. Clumps of cilia on the lateral walls are so dense that underlying surface details are usually obscured. There is a transition zone between the ciliated lateral wall and nonciliated ventral floor. The floor and lower part of the lateral walls of the third ventricle exhibit a characteristic polygonal pattern upon which surface specializations such as microvilli, blebs and polymorphous membrane protrusions are superimposed. Ependyma of the choroid plexus of the third ventricle also display membrane specializations. Supraependymal cells are more visible in nonciliated regions.Supported by USPHS Grants RR-05432, GM-16598 and HD-10010 from the National Institutes of Health and GSRF 171 funds from the University of Washington Graduate School. Portions of this work have been reported previously in abstract form in Anat. Rec. 175, 294 (1973) (before the 86th annual session of the American Association of Anatomists, New York, N.Y., April, 1973)     

The vasotocinergic system in the hypothalamus and limbic region of the budgerigar (Melopsittacus undulatus)

We report a morphological and biochemical analysis on the presence, distribution and quantification of vasotocin in the hypothalamus and limbic region of the budgerigar Melopsittacus undulatus, using immunohistochemistry on serial sections and competitive enzyme linked immunoadsorbent assay measurements on tissue extracts. Analysis of the sections showed large vasotocin-immunoreactive neurons in three main regions of the diencephalon, of both male and female specimens. Vasotocinergic cell bodies were located in the ventral and lateral areas of the hypothalamus, dorsal to the lateral thalamus and medial to the nucleus geniculatus lateralis. Immunoreactive neurons were placed also periventricularly, close to the walls of the third ventricle, at the level of the magnocellular paraventricular nucleus. Well evident bundles of immunoreactive fibers were placed ventral to the anterior commissure in the same regions of the hypothalamus and thalamus where vasotocinergic perikarya are localized. Fibers were identified close to the third ventricle, and in the lateral hypothalamic area along the lateral forebrain bundle. In contrast to what reported for other oscine and non-oscine avian species, we were not able to identify immunopositive neurons in any region above the anterior commissure, or detect relevant differences on the distribution of the vasotocin immmunoreactivity between sexes. Competitive enzyme linked immunoadsorption assay and image analysis of the extension of immunoreactivity in the tissue sections were consistent with the qualitative observations and indicated that there is no statistically significant dimorphism in the content of vasotocin or in the location and distribution of vasotocinergic elements in the investigated areas of male and female parrot brains.     

ACTH1-4 potentiates alpha-MSH-induced melanophore dispersion and excessive grooming

The biological activity and a possible modulatory role of the N-terminal tetrapeptide Ser-Tyr-Ser-Met from alpha-MSH/ACTH was tested in the Anolis melanophore assay, the Xenopus melanophore assay, tyrosinase stimulation in mouse melanoma cells and in excessive grooming in the rat. ACTH1-4 did not exhibit biological activity in any of these four assays nor did it have modulatory properties in the Xenopus and the melanoma cell assay. However, in the Anolis assay ACTH1-4 potentiated pigment dispersion induced by alpha-MSH, alpha-MSH5-13 and ACTH1-24 by a factor of about 2. In the grooming assay ACTH1-4 potentiated the effects of alpha-MSH, alpha-MSH5-13, ACTH1-16 and ACTH5-16, but not those of ACTH1-24. Oxidized ACTH1-4 was without biological activity and potentiating properties in all four assays. This study shows that small fragments of the pro-opiomelanocortin precursor, which are devoid of biological activity, can modulate peripheral and central actions of alpha-MSH/ACTH.     

Thermoregulatory (core, surface and metabolic) responses of unrestrained rats to repeated POAH injections of beta-endorphin or adrenocorticotropin

Repeated preoptic-anterior hypothalamic (POAH) injections of saline and 10 or 25 micrograms/microliters of beta-endorphin or ACTH were given to groups of male Sprague-Dawley rats. One hr after the fifth injection of beta-endorphin or ACTH, each rat received a POAH injection of naloxone HCl (10 micrograms/microliters). Core (Tre-rectal) and surface (Tt-tail) temperatures, metabolic (VO2) and behavioral responses were recorded 30 min before and 60 min after each drug injection. The initial POAH injection of either dose of beta-endorphin produced a hyperthermia. Peak hyperthermia was reduced in the group given 10 micrograms/microliters of beta-endorphin repeatedly. TtS rose after each beta-endorphin injection but temporally lagged Tre increases. Metabolic rate (VO2) was increased with repeated POAH injections of beta-endorphin. Naloxone reduced the elevated Tre seen with beta-endorphin by increasing Tt's further and reducing VO2. POAH administration of ACTH evoked only a slight hyperthermic Tre response, but elevated TtS and VO2S, due to enhanced grooming and explorative behavior. With repeated ACTH injections, TreS did not change from those on the first day as TtS and VO2 remained enhanced. Naloxone reduced VO2 and TtS of the ACTH-treated rats but TreS still were unchanged. Results suggest that the hyperthermia of unrestrained rats given an acute as opposed to repeated POAH beta-endorphin injections is mediated by different effector mechanisms. With the doses used, the slight and unchanging TreS seen with ACTH occurred because this peptide increased heat production due to locomotor activation yet also exaggerated heat loss by vasodilating the peripheral vasculature.     

The effects of neurotensin, naloxone and haloperidol on elements of excessive grooming behavior induced by bombesin

The influence of naloxone, haloperidol and neurotensin was investigated on bombesin-induced excessive grooming in rats. All three drugs reduced the amount of bombesin-induced grooming. Haloperidol induced a general reduction in excessive grooming as induced by bombesin, without changing the composition of grooming behavior, whereas naloxone and neurotensin suppressed bombesin-induced grooming and caused a shift in the distribution of grooming elements. The main suppressive effect of these latter drugs appeared to be on the element scratching. From these data it is suggested that bombesin-induced scratching is mainly displayed by activation of opiate receptor systems, whereas the other elements of bombesin-induced excessive grooming are mainly regulated by dopaminergic systems.     

Alpha MSH-induced excessive grooming behavior involves a GABAergic mechanism.

It has been shown that MSH administered in the ventral tegmental area (VTA) elicits excessive grooming behavior (EGB) by stimulating an acetylcholinergic pathway. The present work was performed in order to evaluate the possible participation of the GABAergic system in this behavior. VTA injection of GABA antagonist bicuculline stimulated the EGB (55.5 +/- 2.4). In contrast, this effect disappeared if the animals were pretreated with atropine (33.1 +/- 1.5). When bicuculline was injected before a 200 ng/microliters dose of MSH, the EGB increased (87.6 +/- 4.4) in comparison to MSH-treated rats (46.5 +/- 3.2). Our results suggest that GABA, ACh, and MSH interact in the VTA in the induction of EGB; an increase in MSH levels appears to stimulate cholinergic neurons. GABAergic fibers probably modulate the cholinergic discharge at the presynaptic level.