Light and scanning electron microscopic study of testosterone-restored penile papillae in castrated rats

Structural changes in various penile tissue from rats with differing circulating androgen levels were analyzed with light and scanning electron microscopy. Adult males were castrated and daily injected for 6 weeks with one of four physiologic amounts of testosterone propionate (TP). Results indicated that epithelium, subepithelial connective tissue, and the papillae protruding from the surface of the glans penis responded, more or less, in a dose-dependent fashion to the steroid. The least androgen-sensitive penile tissue was the epidermal stratum corneum, more sensitive was the maligiphian layer, and more sensitive still was the subepithelium. The penile papillae and their follicles were the most androgen-sensitive tissue. Specifically, the high testosterone, 400 micrograms and 800 micrograms TP, males experienced papillae that were thicker, taller, more densely arranged, and more highly keratinized than the lower testosterone, 100 micrograms and 200 micrograms TP, males. The function of the papillae may be to provide the female with the mechanical stimulation necessary to ensure a proper hormonal milieu for successful impregnation.     

Anisomycin does not disrupt the activation of penile reflexes by testosterone in rats

A possible role of protein synthetic processes in the testosterone-activation of penile reflexes in rats was examined in these experiments. In Experiment 1, long-term castrated male rats were injected with 250 micrograms testosterone propionate (TP) and tested for penile reflexes 24 hr later. Fifteen minutes prior to TP these males received a systemic injection of the protein synthesis inhibitor anisomycin (ANI) or the saline vehicle. ANI had no disruptive effect on the activation of penile reflexes by TP; in fact, ANI facilitated erection frequency. In Experiments 2 and 3, a series of three ANI or saline injections were given at 2 hr intervals beginning with the injection of 250 micrograms TP, with no significant effect on any reflex parameters tested 12 or 24 hr after TP. In Experiment 4, the penile reflexes of male rats were stimulated by implanting a Silastic capsule containing testosterone subcutaneously for 2 weeks. A series of ANI or saline injections were spaced 3 hr apart, with penile reflexes tested 6 and 12 hr after the first injection. There were no significant differences between ANI and saline-treated males at 6 hr, whereas at 12 hr ANI-treated males had significantly shorter reflex latencies and significantly more penile flips than did males injected with saline. In a final experiment (Experiment 5), the Silastic capsules were removed from the males in the previous experiment. Three injections of ANI or saline were given at 4 hr intervals beginning with the removal of the Silastic capsule.(ABSTRACT TRUNCATED AT 250 WORDS)     

Conspecific urine marking in male-female pairs of laboratory rats

Male-female pairs of rats were observed during social interactions for conspecific markings where an animal deposits urine on the body of a second animal. Injections of sodium fluorescein were used to change urinary color and provide a visible mark on the back of a conspecific. The general hypothesis tested in the three experiments was that a female would mark males differently dependent upon her hormonal status and upon the relative hormonal integrity of the males. Results of Experiment 1 were that males marked females more frequently than vice versa and female marking decreased during her estrus. Moreover, a diestrous female marked an aggressive male more than she marked a non-aggressive male (Experiment 2), and a diestrous female marked a castrated male receiving 800 micrograms testosterone propionate (TP) injections more copiously than she marked a castrated male receiving 200 micrograms TP injections (Experiment 3). Finally, aggressive and non-aggressive males marked females similarly, though the 800 micrograms TP males marked females more than the 200 micrograms TP males. These data were compared with findings from research on environmental marking in rodents, and an hypothesis was suggested that female rats use conspecific marking to identify and select males with preferred behavioral and endocrine characteristics.     

Lowered reactivity of rats to androgen in alloxan diabetes

The reactivity of the accessory sex glands of castrated rats to testosterone propionate is considerably lower in animals with alloxan diabetes than in animals with an intact pancreas.     

Effects of neonatal testosterone and estrogen on open-field behaviour in rats

On days 1 and 4 after birth male and female rats from the same litter were injected with either testosterone propionate (TP), or estradiol benzoate (EB) or oil. Subjects were tested in the open-field for 2 minutes per day, for 4 successive days at 45 and 85 days of age. Adult females were significantly more active than males in the outer and inner fields, reared more and defecated less. Neonatal TP and EB treatments reduced activity in females, but only EB increased defaecation in females. EB and TP treated females were heavier than controls at 125 days of age but non-significantly so in the case of TP. Gonadal weights in males and females were reduced in EB and TP treatment, as were penile diameter, number of penile papillae and anogenital spacing in EB treated males. Some of these results are consistent with the argument that androgens defeminize or masculinize certain neural mechanisms in the neonate after first being converted to estrogens, but both EB and TP have anomalous effects on males in producing morphological demasculinization.     

Suprathreshold manipulations of testosterone and reproductive functioning in gonadally intact sexually experienced and inexperienced male rats

Circulating titers of testicular and gonadotrophic hormones differ widely among conspecific mammalain males. The behavioral and physiological consequences of these differences were examined by injecting gonadally intact male rats with extra testosterone or an antiandrogen. Serum testosterone values increased and decreased, respectively, relative to control animals, although all values remained within normal physiological ranges. Results suggested that hormone-sensitive behavior and physiology were related to suprathreshold androgen differences in a dose-response fashion among virgin males. The relationship was more complex among sexually experienced males. Additional testosterone to the experienced males increased the frequency of both aggressive and sexual responding as well as the activity of sex accessory glands. Reductions of circulating testosterone, however, had minimal effects on behavior despite substantial atrophy of hormone-sensitive tissues. Indeed, fecundity was independent of hormone therapy as all experienced males successfully fathered pups. Suprathreshold hormone differences in natural populations of males may reflect sexual selection that is maintained by female choice of a mate.     

Effect of prenatal androgen receptor antagonist or aromatase inhibitor on sexual behavior, partner preference and neuronal Fos responses to estrous female odors in the rat accessory olfactory system

Many socially relevant odors are detected in rodent species by the vomeronasal organ and subsequently processed by the accessory olfactory system (AOS). We previously found that gonadectomized male and female rats treated in adulthood with testosterone propionate (TP) showed equivalent Fos responses in the AOS to odors derived from estrous females. Likewise, in contrast with numerous other mammalian species, gonadectomized female rats show surprisingly high levels of male-typical mounting behavior in response to adult TP. We tested the hypothesis that prenatal testosterone (T) exposure, acting via androgen receptors (ARs) or via estrogen receptors, masculinizes the AOS in rats of both sexes. Pregnant dams were treated with either the AR blocker, Flutamide, the aromatase inhibitor, 1,4,6-androstatriene-3,17-dione (ATD), or nothing (control) to assess the role of prenatal androgen and estradiol receptor activation, respectively, in this masculinization. Beginning at birth, male and female offspring were injected subcutaneously (sc) every other day with either ATD (pre- and neonatal ATD group) or oil vehicle (Flutamide and control groups) until postnatal Day 12. Subjects were gonadectomized as adults, hormonally treated and tested for different behaviors before having their AOS Fos responses to estrous female odors assessed. Prenatal treatment with Flutamide (but not ATD) significantly decreased anogenital distance and severely impaired intromissive and ejaculatory behaviors in males tested after TP replacement without disrupting mounting capacity in either sex. Pre- and neonatal treatment with ATD (but not Flutamide) enhanced lordosis responsiveness in males tested after sc injections of estradiol and progesterone, whereas these perinatal treatments had no effect on any aspect of masculine coital performance in either sex. After TP treatment, male and female control subjects preferred to approach a tethered stimulus female as opposed to a male, and prenatal Flutamide or perinatal ATD treatments did not modify this pattern of partner preference. Neuronal Fos responses to estrous odors were (as in previous studies) identical in the AOS of gonadectomized TP-treated control males and females. Prenatal Flutamide or perinatal ATD treatments failed to disrupt consistently this profile of Fos responses to estrous odors in the AOS of rats of either sex. These behavioral and neuroanatomical findings raise the possibility that the similar level of male-typical responsiveness to social odors that occurs in male and female rats after adult TP treatment results from nonsteroid-hormone-dependent, species-specific factors that act perinatally in the brains of rats of both sexes.     

Effects of corticotropin releasing factor on genetically obese (fatty) rats

Corticotropin releasing factor (CRF) has been administered into the third ventricle of lean and genetically obese Zucker fatty rats in both acute and chronic experiments. Following a single injection of CRF (5 micrograms or approximately 1 nmole) there was an acute reduction of food intake in both the lean and obese animals, but the effect was greater in the obese. This effect persisted for the first three hours but was no longer detectable in either lean or genetically obese animals at 6 hours. Binding of GDP to mitochondria from interscapular brown adipose tissue in 21-hour deprived animals was lower in the fatty rats than in the lean controls. The injection of CRF significantly increased GDP binding in both the lean and fatty rats. During chronic infusion of CRF into the third ventricle of fatty rats, there was a significant decrease in food intake in the obese rats and fall of body weight in both groups. The basal levels of GDP binding were significantly lower in the saline-infused fatty rats than in the saline-infused lean controls. The chronic infusion of CRF increased GDP binding in the fatty rats but not in the lean animals. The CRF-treated values for GDP binding in fatty rats however, remained significantly below the baseline values in the control animals. Chronic CRF infusion also significantly lowered glucose levels in the fatty rat. These studies are consistent with the hypothesis that CRF may be involved in the decreased food intake and increased sympathetic activity observed in genetically obese fatty rats following adrenalectomy.     

Arthritis induced by interleukin-1 is dependent on the site and frequency of intraarticular injection

Intraarticular injection of recombinant human interleukin-1 (IL-1) in rats resulted in varying degrees of inflammatory changes depending on the site and frequency of injections. (i) Much lower amounts of IL-1 were required to elicit an inflammatory response in the ankle joints (15-3000 ng) than the knee joints (90-150 micrograms). (ii) The inflammatory response was much greater if IL-1 was administered in multiple doses as compared to a single dose injection. One day after a single injection of IL-1 (90-150 micrograms), knee joints exhibited a mild increase in volume as a consequence of edema, but at the end of 1 week, no discernible change in volume was observed. However, when the same total amount of IL-1 was injected in three doses, there was a dramatic increase in joint volume at the end of 1 week that persisted for at least 3 weeks. The increase was dose dependent. (iii) The inflammatory response was dependent on the age/weight of the rats: the older the animals the greater the response. (iv) Under conditions where IL-1 induced inflammatory changes in knee joints, recombinant tumor necrosis factor failed to induce any significant response. (v) Histological examination of the knee joints revealed distinct differences in the pathological response to the two different protocols of IL-1 administration in the knee joints. The animals injected with a single dose of IL-1 showed a mild and transient inflammation that was resolved by 2 weeks postinjection, but exhibited degenerative changes associated with focal loss of chondrocytes and proteoglycan of the knee joint cartilage, which became progressively severe. The knee joints of animals given three injections of IL-1 showed evidence of marked acute synovitis, fibroplasia, loss of proteoglycan and chondrocytes, resorption of subchondral bone, and transition of hematopoeitic marrow cells into cells of mesenchymal morphology. (vi) Examination of proteoglycan synthesis by cartilage of IL-1-injected rats revealed that within 1 day after injection, a dramatic reduction in synthesis occurred which persisted for at least 2 weeks. These studies suggest that intraarticular injection of IL-1 provides a useful rodent model for the investigation of pathological changes occurring within a localized joint as a result of acute and chronic inflammatory stimuli. Relevant aspects of the pathology of joint erosion can be demonstrated depending on the frequency of IL-1 injection.     

Sexual behaviour of male rats injected with the anti-oestrogen MER-25 during infancy

Newborn male rats were injected SC with 50, 100 or 200 micrograms MER-25 or 0.05 ml oil daily for the first 10 days of life. As adults, they were tested for male sexual behaviour both before and after castration and replacement with testosterone propionate, and for female sexual behaviour after injections of oestradiol benzoate followed by progesterone. Injections of 100 and 200 micrograms MER-25/day during infancy caused significantly fewer rats to ejaculate than 0.05 ml oil/day in both series of tests for male sexual behaviour. The reduced occurrence of ejaculation could not be related to defective penile development as there was no significant difference in penis weights or the numbers of penile spines between the MER-25 and oil-injected rats. All doses of MER-25 caused significantly more lordosis behaviour after oestrogen and progesterone than did injections of oil. These results provide further evidence that neonatal testicular androgens must be converted to oestrogen in the brain in order to organise male sexual behaviour patterns, including the neural substrate for ejaculation, as well as to suppress female sexual behaviour.     

Pancreatic glucagon does not alter intrameal gastric emptying of milk in the rat

The hypothesis that pancreatic glucagon (PG) inhibits feeding by altering intrameal gastric emptying was tested in nondeprived rats at midday, conditions under which exogenous PG is thought to elicit satiety. Rats received intraperitoneal injections of PG (400 or 800 micrograms/kg), cholecystokinin (CCK, 0.5 or 1.0 micrograms/kg) or saline and were given bolus intragastric infusions of 10 ml evaporated milk through chronic gastric cannulae. PG did not affect volumes of stomach contents recovered 20 minutes postinjection. In contrast, CCK inhibited gastric emptying in a dose-related manner. When milk was offered to the same rats to drink, 400 micrograms/kg PG significantly reduced meal size. These findings suggest that PG's satiety effect is not caused by its effect on stomach emptying.     

Pathologic changes in the accessory sex glands of rats treated with a sympatholytic hypotensive agent (losulazine)

Groups of 25 male Sprague-Dawley rats were treated by gastric intubation with either vehicle control (modified methylcellulose) or a suspension of losulazine at 4, 8, 16, or 32 mg/kg/day for 1 yr. Ten rats/group were killed after 6 months of treatment. Reversibility of drug-induced changes was evaluated in 8 rats/group treated for 6 months and held without treatment for 5 months. Daily clinical signs and weekly body weight changes were monitored. Seminal vesicle/coagulating glands were weighed in rats treated for 6 months. Gross and microscopic evaluation of the accessory sex glands (ampullary glands, prostate, seminal vesicles and coagulating glands) was conducted in all rats killed at 6 months, after the recovery period, and in rats that survived through the one-yr treatment period. Ptosis, somnolence, and fecal softening were detected in all groups treated with losulazine. There was a nonreversible body weight gain retardation in groups treated with 8 to 32 mg/kg/day of losulazine for 6 months or 1 yr. Absolute and relative weights of the seminal vesicle/coagulating glands of treated rats were not significantly different from those of control rats. The ventral prostate in a few rats in all treated groups had yellow to tan granular foci. Treatment, but not dose-related sperm granulomas or glandular impaction with inspissated secretion (formation of corpora amylacia) in the ampullary glands, enhanced cellular exudation into the acini of the ventral prostate, and impaction of the seminal vesicles with altered granular to globular secretion were found in rats treated with losulazine.(ABSTRACT TRUNCATED AT 250 WORDS)     

Progesterone,estradiol, testosterone and dihydrotestosterone: Effects on rate of extinction of a conditioned taste aversion in rats

An investigation was made to determine why the prolonged rate of extinction of a conditioned taste aversion induced by testosterone is diminished when the ovarian system is intact. In the first experiment, 36 gonadectomized female rats received injections of progesterone, testosterone propionate (TP), progesterone plus TP, or sesame oil. Progesterone did not reduce the slow extinction rate induced by TP. In a second experiment, 36 gonadectomized female rats received injections of estradiol dipropionate (EP), TP, EP plus TP, or sesame oil. Estradiol dipropionate reduced the effectiveness of TP in prolonging the extinction rate. These same results (the ineffectiveness of progesterone and the effectiveness of EP in blocking TP-induced slow extinction) were also observed in male rats in a third experiment. Dihydrotestosterone, as well as testosterone, has been shown to prolong extinction: hence, in a fourth experiment 30 gonadectomized female rats received injections of EP, TP, dihydrotestosterone propionate (DHTP), EP plus DHTP, or sesame oil. Estradiol dipropionate reduced the DHTP-induced slow extinction. All the above data are consistent with the hypothesis that it is estradiol from the ovaries that diminishes the effect of testosterone on the rate of extinction of a conditioned taste aversion in intact females.     

Morphologic alterations in the trachea and the salivary gland following the induction of rapid synchronous vitamin A deficiency in rats.

The use of the synchronous induction method enables both assessment of the sequence and reliability of the appearance of morphologic signs of vitamin A deficiency, and their accurate correlation with biochemical and physiologic abnormalities. In the trachea, hyperplasia of basal epithelial cells was observed by Day 4 (T4) following the withdrawal of retinoic acid from retinoate-cycled, stringently deficient rats. Keratinization was observed by Day 6, the upper part of the trachea showing the highest incidence of keratinization. All such metaplastic changes originated in the narrow strip of tissue directly cojoining the esophagus. In the submaxillary glands, atrophy of the acini, an increase in interlobular spaces, and fibrosis and dilatation of the ducts was observed by Day 10. In more advanced stages of deficiency (T14-T18), cyst formation associated with suppuration and extensive cell atrophy was observed. Morphologic changes were less marked in the sublingual glands, although mucin levels were noticeably depressed by Day 12 of deficiency. Following the oral dosing of deficient animals (T12) with 350 micrograms retinyl palmitate, all such changes were reversed within 6 days in the trachea and within 10 days in the submaxillary and sublingual glands. Similar patterns were observed whether animals were force-fed or were fed ad libitum. Apart, therefore, from cause-effect considerations per se, morphologic changes are also potentially valuable reference indicators of deficiency, particularly in time course studies, or where force-feeding attenuates other signs of deficiency.     

Precocious development of granular convoluted tubules in the mouse submandibular gland induced by thyroxine or by thyroxine and testosterone

The effects of the administration of thyroxine (T₄) and/or testosterone (TP) on the early postnatal differentiation of granular convoluted tubule (GCT) cells of the submandibular glands were studied in Swiss-Webster mice. From birth, mice were injected daily with T₄ up to the time of killing at 15 or 20 days of age. In addition, groups of mice were given one injection of TP eight days before killing. Control animals received vehicles (saline and/or sesame oil). Sections of the glands were stained with toluidine blue, or immunocytochemically by the unlabelled antibody enzyme method, for the localization of protease A, epidermal growth factor, or renin. Supernatants of the gland were analyzed for protease activity (pH 8.5, substrate: tosyl-glyclyl-L-prolyl-L-arginine nitroanilide acetate), or by radioimmunoassay for EGF content. At 15 days of age no GCT cells were present in the glands of control or TP-treated mice. In T₄-injected mice many small GCT cells occurred, while larger and more numerous GCT cells were seen in the glands of mice that received both hormones. TP alone had no effect on levels of EGF or protease activity. In T₄-treated mice, protease levels increased 10-fold and EGF content rose 28-fold. TP administration to T₄-treated mice caused a further threefold, increase in both protease activity and EGF content. At 20 days of age the glands of control mice had a few small GCT cells, and both protease activity and EGF content were substantially increased. TP treatment was again without effect. However, daily injections of T₄ caused both protease activity and EGF levels to increase 20- and 11-fold, respectively. Just as in 15-day-old mice, TP administration to T₄-primed mice resulted in further increases in the two polypeptides. Immunocytochemical staining for protease A and EGF confirmed the chemical data. Renin was detectable immunocytochemically at both ages in the glands of mice that had received T₄, but it was seen in the glands of mice that had received TP alone only at 20 days of age. It is concluded that T₄ caused a precocious induction of GCT cells and their specific products. Although TP alone had no effect on their early differentiation, it acted synergistically with T₄ in inducing GCT cells. There were no obvious sex differences in any of these features in control or treated animals.     

Antigen-Induced Inhibition of Autoimmune Response to Rat Male Accessory Glands

ABSTRACT: Pretreatment of rats with low doses of purified fraction of rat male accessory glands (containing the autoantigen) markedly reduced the immune response to autoantigen when animals were subsequently challenged with modified rat male accessory glands in complete Freund's adjuvant. The rats pretreated with low doses of antigen prior to immunization showed marked suppression of delayed-type hypersensitivity reaction (P < 0.001) when compared to control animals (pretreated with rat lung saline extract or 0.15 M NaCl). There was also enhancement of migration of macrophages in test male rats, whereas the migration was inhibited in control male rats (P < 0.01). The stimulation of migration found in the male rats in which the response was inhibited would suggest the presence of a migration stimulation factor, which is considered a marker of suppressor cell activity. Humoral immunity was also reduced. Pretreatment of rats with low doses of the antigen markedly reduced the immune response, probably because of the induction of suppressor cells.     

Internalization of mu-opioid receptors produced by etorphine in the rat locus coeruleus.

Chronic administration of mu-opioid receptor agonists is known to produce adaptive changes within noradrenergic neurons of the locus coeruleus. Although mu-opioid receptors are densely expressed by locus coeruleus neurons, the effects of acute and chronic administration of agonists on the subcellular distribution of mu-opioid receptors remain poorly understood. Therefore, we examined the ultrastructural distribution of mu-opioid receptor immunoreactivity in the locus coeruleus of rats subjected to either acute morphine, or etorphine, or chronic morphine treatment. In the locus coeruleus of control rats receiving acute saline injections or placebo pellet implants, immunogold-silver labeling for mu-opioid receptors was localized to parasynaptic and extrasynaptic portions of the plasma membranes of perikarya and dendrites. Only 8% of the gold-silver particles analyzed were distributed within the cytoplasm of dendrites and perikarya in vehicle-treated rats. Immunolabeling for mu-opioid receptors was distributed along portions of the plasma membrane that were often apposed by astroglial sheaths. After acute injections of etorphine, there was a dramatic internalization of mu-opioid receptors to intracellular compartments. Quantitative analysis of gold-silver particles indicative of mu-opioid receptors showed that a substantial number of gold particles shifted from the plasma membrane to early endosomes in dendrites from etorphine-treated rats. In dendrites sampled from etorphine-treated rats, 85% of the gold-silver grains indicative of mu-opioid receptor labeling were located in intracellular compartments as compared to 15% that were distributed along the plasma membrane. In animals that received either acute morphine injections or chronic morphine via pellet implantation, no change in the subcellular distribution of immunogold particles indicative of mu-opioid receptors was detected when compared to matched control animals.These results provide the first ultrastructural evidence that mu-opioid receptors are internalized by agonists such as etorphine, but not the partial agonist morphine, in the locus coeruleus.     

Age-related changes in rat hepatic and renal thyroid hormone-sensitive enzymes--different responses to acute and chronic L-triiodothyronine stimulation

Using young (5-6 weeks) and adult (12-14 months) male Sprague-Dawley rats, the responses of hepatic and renal cytosolic malic enzymes (ME) and mitochondrial alpha-glycerophosphate dehydrogenase (alpha-GPDH), have been assessed following acute and chronic L-triiodothyronine (T3) administration. In control (untreated) animals a significant reduction of renal ME as well as hepatic and renal alpha-GPDH activity with increased age were observed but renal ME activity was not age-related. Following acute T3 stimulation (200 micrograms T3/100 g body wt single injection), the levels of hepatic ME and alpha-GPDH as well as renal alpha-GPDH but not renal ME remained lower in the adult than in the younger group. After chronic T3 stimulation (15 micrograms T3/100 g body wt for 7 days) or 200 micrograms T3/100 g body wt for 4 days), the enzyme levels remained significantly lower in older animals for hepatic ME but were no longer different for hepatic and renal alpha-GPDH, while renal ME, which was not altered with age, had values that were the same as in the younger group. These studies have demonstrated that age-related changes in hepatic and renal T3-sensitive enzymes could not be attributed solely to T3 occupancy of nuclear receptor binding sites, but may be influenced by other factors depending upon the specific tissues and subcellular T3-sensitive enzymes being assessed.     

A comparison of the effects of bilateral sections of the chorda tympani nerve and extirpation of the submaxillary and sublingual salivary glands on the eating and drinking patterns of the rat

The chorda tympani nerve (CT) innervates the fungiform papillae on the tip of the tongue and has been considered an important nerve for the sense of taste. The CT also contains the parasympathetic supply to the submaxillary and sublingual salivary glands. Therefore, changes in taste or feeding behavior following bilateral sections of CT are caused by both degeneration of fungiform papillae and the inevitable partial desalivation of the rat. In the present experiments we compared the effects of bilateral chorda tympani nerve sections with extirpation of submaxillary and sublingual glands on daily home cage eating and drinking patterns in the rat. Before and after surgery we analyzed the daily eating and drinking patterns, including such measures as intake, bout number, bout length, interbout interval and rate of consumption during bouts. The results of desalivation and bilateral CT sections were indistinguishable. The most profound change was that eating bout duration was increased following surgery. Since food intake did not increase, the results indicate a marked loss in eating efficiency over the daily ingestion periods. Although the eating patterns of desalivated and chorda tympani sectioned rats are quite similar, the evidence is not compelling that they have the same physiological basis. A second experiment was designed to test the hypothesis that the atypical eating patterns observed following bilateral sectioning of CT were the direct result of partial desalivation resulting from the denervation of the salivary glands. In this experiment a unilateral section was made of one CT and it was shown that the eating behavior was not affected. Then the contralateral submaxillary and sublingual salivary glands were removed. This resulted in a six-fold increase in feeding bout length. In all cases a unilateral CT section combined with extirpation of the contralateral salivary glands resulted in rats whose eating behavior was indistinguishable from the earlier data following either the bilateral CT sections or bilateral desalivations. The conclusion is drawn that the eating irregularities noted following bilateral CT sections result from this partial desalivation. CT sections were verified by taste bud counts in the fungiform papillae and histological examinations were made of salivary glands in rats receiving CT sections.